Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

On 11/11/2013 12:38, Jay wrote:
Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

A guess, but have you considered the diode capacitance and corresponding
FET switch-on current?

I would imagine the PIC has a short rise-time?

Given coil current is only 30mA I would put a 100R resistor in series
with the diode, would also make for a faster turn-off.

The 2N7002 has a rated current of 300mA.

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

The PIC18F452 pin 5 (RD7/PSP7), is that high-side-only drive? If so,
the 10K G-S pull-down is inadequate for quick turn-off, and the 2N7000
dissipates to death.

Or it could be the other way around and the PIC can't raise the gate
voltage quickly enough due to its large capacitance. Likewise a slow
death due to dissipation.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

---
Dunno, but a 1N4002 isn't a Schottky.

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

There should be a series gate resistor, particularly if J2 (if it is the
processor, and not a cable) is more than a few cm from the transistor.
Sometimes not even that. 100-1k ohm would be plenty, installed right at
the gate.

Just out of habit, I would specify a BJT for the switch, which I think
saves a few cents and not much else (the series base resistor is
required). Seems unlikely that the coil would fail shorted (so a current
limited switch would be desirable) or generate spikes more than normal
(demanding better spike protection, e.g., RCD snubber).

Tim

--
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

"Jay" wrote in message
...
Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay
coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that
it
will run for quite awhile, perhaps 20 to 30 thousand cycles before
failing
entirely shorted Drain to Source.

Thanks.

On 11/11/2013 4:38 AM, Jay wrote:
Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

What do you see when you put a voltage probe and a current probe on the
drain
and look at 'em with a scope...initially and some time later near failure?
A digital scope with multiplication capability will make the job easier.

Thermal cycling of the chip can kill it even way below max average
dissipation.

What's the gate resistor for?
If you're driving it from low impedance, you don't need it.
If you do need it, it's too big. Miller capacitance may be what's
killing you.

In article ,
Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

There may be a second voltage bounce on the coil that's pushing the
drain to -1V and pushing the gate as low as -14V through capacitive
coupling. It could be making your PIC go nuts in ways that induces high
voltage resonance on the gate drive or sends high currents/frequencies
through your slow bypass diode (D5).

It looks like one simple solution would be to add a fast diode between
the FET and the PIC. That would keep negative voltages out of the PIC
and prevent any high frequency interactions from happening.

If the PIC has a low impedance output that doesn't mind some negative
voltage, place a resistor in series with the gate to slow down the FET.

On Mon, 11 Nov 2013 09:23:30 -0600 John Fields
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

---
Dunno, but a 1N4002 isn't a Schottky.

Yeah, I noticed that as well. It's not my schematic, though. Thanks.

On Mon, 11 Nov 2013 08:16:16 -0700 Jim Thompson
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

The PIC18F452 pin 5 (RD7/PSP7), is that high-side-only drive? If so,
the 10K G-S pull-down is inadequate for quick turn-off, and the 2N7000
dissipates to death.

Or it could be the other way around and the PIC can't raise the gate
voltage quickly enough due to its large capacitance. Likewise a slow
death due to dissipation.

...Jim Thompson

Hi Jim,

Thanks. I think your second thought may be right. I took a scope capture
of the gate at turn on. (Attached)
Think that could be the culprit? Any ideas to get rid of it?

To address Tim's question:
The total trace length including wire is about 6" or so between the PIC
and the FET. 4" of that is on a ribbon cable between two connectors.
The diode is at the coil, not the FET.

Turn off looks fine, no ringing or anything...

Thanks everybody for your suggestions.

Tim Williams wrote:
Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)
* NO, a/the "snubbing" diode should be across the coil, preferably with
a series current limiting resistor.
The diode shunts the voltage created by di/dt at turnoff, and a
series resistor reduces the coil current at that time, speeding the
relay turnoff.
Voltage spikes are created by the coil di/dt, not by the switch
transistor.


There should be a series gate resistor, particularly if J2 (if it is the
processor, and not a cable) is more than a few cm from the transistor.
Sometimes not even that. 100-1k ohm would be plenty, installed right at
the gate.

Just out of habit, I would specify a BJT for the switch, which I think
saves a few cents and not much else (the series base resistor is
required).
* Yes, can be more robust in this app: SOA and peak voltage.

Seems unlikely that the coil would fail shorted (so a current
limited switch would be desirable)
* Have never seen a relay coil shorted in 50+ years.

or generate spikes more than normal
(demanding better spike protection, e.g., RCD snubber).

Tim

On Tue, 12 Nov 2013 08:45:16 -0500, Jay wrote:

On Mon, 11 Nov 2013 08:16:16 -0700 Jim Thompson
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

The PIC18F452 pin 5 (RD7/PSP7), is that high-side-only drive? If so,
the 10K G-S pull-down is inadequate for quick turn-off, and the 2N7000
dissipates to death.

Or it could be the other way around and the PIC can't raise the gate
voltage quickly enough due to its large capacitance. Likewise a slow
death due to dissipation.

...Jim Thompson

Hi Jim,

Thanks. I think your second thought may be right. I took a scope capture
of the gate at turn on. (Attached)
Think that could be the culprit? Any ideas to get rid of it?

To address Tim's question:
The total trace length including wire is about 6" or so between the PIC
and the FET. 4" of that is on a ribbon cable between two connectors.
The diode is at the coil, not the FET.

Turn off looks fine, no ringing or anything...

Thanks everybody for your suggestions.

The time spent in that flat spot (gate charge plateau) is probably
what is getting you.

I'd probably rig up a bipolar driver between the micro and the gate.

More detail as to ON/OFF rate, etc?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Tue, 12 Nov 2013 08:14:31 -0700, Jim Thompson
wrote:

On Tue, 12 Nov 2013 08:45:16 -0500, Jay wrote:

On Mon, 11 Nov 2013 08:16:16 -0700 Jim Thompson
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

The PIC18F452 pin 5 (RD7/PSP7), is that high-side-only drive? If so,
the 10K G-S pull-down is inadequate for quick turn-off, and the 2N7000
dissipates to death.

Or it could be the other way around and the PIC can't raise the gate
voltage quickly enough due to its large capacitance. Likewise a slow
death due to dissipation.

...Jim Thompson

Hi Jim,

Thanks. I think your second thought may be right. I took a scope capture
of the gate at turn on. (Attached)
Think that could be the culprit? Any ideas to get rid of it?

To address Tim's question:
The total trace length including wire is about 6" or so between the PIC
and the FET. 4" of that is on a ribbon cable between two connectors.
The diode is at the coil, not the FET.

Turn off looks fine, no ringing or anything...

Thanks everybody for your suggestions.

The time spent in that flat spot (gate charge plateau) is probably
what is getting you.

I'd probably rig up a bipolar driver between the micro and the gate.

More detail as to ON/OFF rate, etc?

...Jim Thompson

Sheeesh! It just occurred to me... the easy fix... One package of
74HC04 (or the small package equivalent). Parallel 5 of the six
inverters for directly driving the gate, then one inverter between
micro and the 5-paralleled ones. That ought to speed up things a bit
;-)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On 11/12/2013 7:38 AM, Jim Thompson wrote:
On Tue, 12 Nov 2013 08:14:31 -0700, Jim Thompson
wrote:

On Tue, 12 Nov 2013 08:45:16 -0500, Jay wrote:

On Mon, 11 Nov 2013 08:16:16 -0700 Jim Thompson
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

The PIC18F452 pin 5 (RD7/PSP7), is that high-side-only drive? If so,
the 10K G-S pull-down is inadequate for quick turn-off, and the 2N7000
dissipates to death.

Or it could be the other way around and the PIC can't raise the gate
voltage quickly enough due to its large capacitance. Likewise a slow
death due to dissipation.

...Jim Thompson

Hi Jim,

Thanks. I think your second thought may be right. I took a scope capture
of the gate at turn on. (Attached)
Think that could be the culprit? Any ideas to get rid of it?

To address Tim's question:
The total trace length including wire is about 6" or so between the PIC
and the FET. 4" of that is on a ribbon cable between two connectors.
The diode is at the coil, not the FET.

Turn off looks fine, no ringing or anything...

Thanks everybody for your suggestions.

The time spent in that flat spot (gate charge plateau) is probably
what is getting you.

I'd probably rig up a bipolar driver between the micro and the gate.

More detail as to ON/OFF rate, etc?

...Jim Thompson

Sheeesh! It just occurred to me... the easy fix... One package of
74HC04 (or the small package equivalent). Parallel 5 of the six
inverters for directly driving the gate, then one inverter between
micro and the 5-paralleled ones. That ought to speed up things a bit
;-)

...Jim Thompson

Am I the only one old enough to remember the days when we used
to IDENTIFY a problem before we started throwing solutions at it?

You really need to plot the voltage AND the current in the FET
on BOTH edges.

I'm gonna make a big leap here cuz I don't know the current in the relay
relative to the capabilities of the FET. A quick look at the spec
suggests that, using the worst
case specs, there's plenty of room for the possibility that this is the
WRONG FET for the task.

If it's low-impedance pullup-only drive. Otherwise Miller can
eat your lunch at turn-on too.
If it really is Miller effect. And IF reducing the gate resistor
from 10K to 1K really does reduce the discharge time by a factor of
10.
Might that solve the problem?
Should be trivial to tell by looking at the CURRENT X Voltage profile
at the drain and gate.

I'm not saying you shouldn't fix it, but it is curious that you have
the remote alarm with mechanical relay going off 30,000 times.

On Tue, 12 Nov 2013 17:16:41 -0800, mike wrote:

On 11/12/2013 7:38 AM, Jim Thompson wrote:
On Tue, 12 Nov 2013 08:14:31 -0700, Jim Thompson
wrote:

On Tue, 12 Nov 2013 08:45:16 -0500, Jay wrote:

On Mon, 11 Nov 2013 08:16:16 -0700 Jim Thompson
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

The PIC18F452 pin 5 (RD7/PSP7), is that high-side-only drive? If so,
the 10K G-S pull-down is inadequate for quick turn-off, and the 2N7000
dissipates to death.

Or it could be the other way around and the PIC can't raise the gate
voltage quickly enough due to its large capacitance. Likewise a slow
death due to dissipation.

...Jim Thompson

Hi Jim,

Thanks. I think your second thought may be right. I took a scope capture
of the gate at turn on. (Attached)
Think that could be the culprit? Any ideas to get rid of it?

To address Tim's question:
The total trace length including wire is about 6" or so between the PIC
and the FET. 4" of that is on a ribbon cable between two connectors.
The diode is at the coil, not the FET.

Turn off looks fine, no ringing or anything...

Thanks everybody for your suggestions.

The time spent in that flat spot (gate charge plateau) is probably
what is getting you.

I'd probably rig up a bipolar driver between the micro and the gate.

More detail as to ON/OFF rate, etc?

...Jim Thompson

Sheeesh! It just occurred to me... the easy fix... One package of
74HC04 (or the small package equivalent). Parallel 5 of the six
inverters for directly driving the gate, then one inverter between
micro and the 5-paralleled ones. That ought to speed up things a bit
;-)

...Jim Thompson

Am I the only one old enough to remember the days when we used
to IDENTIFY a problem before we started throwing solutions at it?

You really need to plot the voltage AND the current in the FET
on BOTH edges.

I'm gonna make a big leap here cuz I don't know the current in the relay
relative to the capabilities of the FET. A quick look at the spec
suggests that, using the worst
case specs, there's plenty of room for the possibility that this is the
WRONG FET for the task.

If it's low-impedance pullup-only drive. Otherwise Miller can
eat your lunch at turn-on too.
If it really is Miller effect. And IF reducing the gate resistor
from 10K to 1K really does reduce the discharge time by a factor of
10.
Might that solve the problem?
Should be trivial to tell by looking at the CURRENT X Voltage profile
at the drain and gate.

I'm not saying you shouldn't fix it, but it is curious that you have
the remote alarm with mechanical relay going off 30,000 times.

Huh? Too many tokes ?:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Tue, 12 Nov 2013 08:38:35 -0700 Jim Thompson
wrote in Message id:
:

On Tue, 12 Nov 2013 08:14:31 -0700, Jim Thompson
wrote:

On Tue, 12 Nov 2013 08:45:16 -0500, Jay wrote:

On Mon, 11 Nov 2013 08:16:16 -0700 Jim Thompson
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

The PIC18F452 pin 5 (RD7/PSP7), is that high-side-only drive? If so,
the 10K G-S pull-down is inadequate for quick turn-off, and the 2N7000
dissipates to death.

Or it could be the other way around and the PIC can't raise the gate
voltage quickly enough due to its large capacitance. Likewise a slow
death due to dissipation.

...Jim Thompson

Hi Jim,

Thanks. I think your second thought may be right. I took a scope capture
of the gate at turn on. (Attached)
Think that could be the culprit? Any ideas to get rid of it?

To address Tim's question:
The total trace length including wire is about 6" or so between the PIC
and the FET. 4" of that is on a ribbon cable between two connectors.
The diode is at the coil, not the FET.

Turn off looks fine, no ringing or anything...

Thanks everybody for your suggestions.

The time spent in that flat spot (gate charge plateau) is probably
what is getting you.

I'd probably rig up a bipolar driver between the micro and the gate.

More detail as to ON/OFF rate, etc?

...Jim Thompson

Sheeesh! It just occurred to me... the easy fix... One package of
74HC04 (or the small package equivalent). Parallel 5 of the six
inverters for directly driving the gate, then one inverter between
micro and the 5-paralleled ones. That ought to speed up things a bit

Thanks Jim. That worked great to get that flat spot out.

On Wed, 13 Nov 2013 10:20:29 -0500, JW wrote:

On Tue, 12 Nov 2013 08:38:35 -0700 Jim Thompson
wrote in Message id:
:

On Tue, 12 Nov 2013 08:14:31 -0700, Jim Thompson
wrote:

On Tue, 12 Nov 2013 08:45:16 -0500, Jay wrote:

On Mon, 11 Nov 2013 08:16:16 -0700 Jim Thompson
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

The PIC18F452 pin 5 (RD7/PSP7), is that high-side-only drive? If so,
the 10K G-S pull-down is inadequate for quick turn-off, and the 2N7000
dissipates to death.

Or it could be the other way around and the PIC can't raise the gate
voltage quickly enough due to its large capacitance. Likewise a slow
death due to dissipation.

...Jim Thompson

Hi Jim,

Thanks. I think your second thought may be right. I took a scope capture
of the gate at turn on. (Attached)
Think that could be the culprit? Any ideas to get rid of it?

To address Tim's question:
The total trace length including wire is about 6" or so between the PIC
and the FET. 4" of that is on a ribbon cable between two connectors.
The diode is at the coil, not the FET.

Turn off looks fine, no ringing or anything...

Thanks everybody for your suggestions.

The time spent in that flat spot (gate charge plateau) is probably
what is getting you.

I'd probably rig up a bipolar driver between the micro and the gate.

More detail as to ON/OFF rate, etc?

...Jim Thompson

Sheeesh! It just occurred to me... the easy fix... One package of
74HC04 (or the small package equivalent). Parallel 5 of the six
inverters for directly driving the gate, then one inverter between
micro and the 5-paralleled ones. That ought to speed up things a bit

Thanks Jim. That worked great to get that flat spot out.

Glad to hear it worked out for you!

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

What's the actual gate drive voltage?


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

On Wed, 13 Nov 2013 19:28:02 -0800 John Larkin
wrote in Message id:
:

On Mon, 11 Nov 2013 07:38:52 -0500, Jay wrote:

Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that it
will run for quite awhile, perhaps 20 to 30 thousand cycles before failing
entirely shorted Drain to Source.

Thanks.

What's the actual gate drive voltage?

About 5 volts or so. You must have missed the scope capture. Anyway I'm
all set, JT's idea of using a 74HC04 worked well.
Thanks.

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson


Whenever "Thompson" and "inductance" show up in the same post, amusement is sure
to follow.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

On Mon, 18 Nov 2013 09:34:16 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson


Whenever "Thompson" and "inductance" show up in the same post, amusement is sure
to follow.

Wiring inductance _between_device_and_catch_diode_ can cause voltage
spikes, depending on device turn-off speed... irrespective of what
smug-ass comments Larkin may churn up.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Mon, 18 Nov 2013 11:14:39 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 09:34:16 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson


Whenever "Thompson" and "inductance" show up in the same post, amusement is sure
to follow.

Wiring inductance _between_device_and_catch_diode_ can cause voltage
spikes, depending on device turn-off speed... irrespective of what
smug-ass comments Larkin may churn up.

...Jim Thompson

Show us.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

On Mon, 18 Nov 2013 10:30:05 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 11:14:39 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 09:34:16 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
m wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson


Whenever "Thompson" and "inductance" show up in the same post, amusement is sure
to follow.

Wiring inductance _between_device_and_catch_diode_ can cause voltage
spikes, depending on device turn-off speed... irrespective of what
smug-ass comments Larkin may churn up.

...Jim Thompson

Show us.

See attachment. Sorry that Larkin is incapable of understanding the
basic behavior of _any_ inductance.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Mon, 18 Nov 2013 12:25:28 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 10:30:05 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 11:14:39 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 09:34:16 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson


Whenever "Thompson" and "inductance" show up in the same post, amusement is sure
to follow.

Wiring inductance _between_device_and_catch_diode_ can cause voltage
spikes, depending on device turn-off speed... irrespective of what
smug-ass comments Larkin may churn up.

...Jim Thompson

Show us.

See attachment. Sorry that Larkin is incapable of understanding the
basic behavior of _any_ inductance.

...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)




--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

On Mon, 18 Nov 2013 13:20:14 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 12:25:28 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 10:30:05 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 11:14:39 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 09:34:16 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
m wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
m wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson


Whenever "Thompson" and "inductance" show up in the same post, amusement is sure
to follow.

Wiring inductance _between_device_and_catch_diode_ can cause voltage
spikes, depending on device turn-off speed... irrespective of what
smug-ass comments Larkin may churn up.

...Jim Thompson

Show us.

See attachment. Sorry that Larkin is incapable of understanding the
basic behavior of _any_ inductance.

...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)

No amount of bloviation will cover your ignorance... wiring out to a
solenoid or relay before the catch diode will give you grief.

No matter how many times you bloviate.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Mon, 18 Nov 2013 14:25:27 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 13:20:14 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 12:25:28 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 10:30:05 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 11:14:39 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 09:34:16 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
om wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson


Whenever "Thompson" and "inductance" show up in the same post, amusement is sure
to follow.

Wiring inductance _between_device_and_catch_diode_ can cause voltage
spikes, depending on device turn-off speed... irrespective of what
smug-ass comments Larkin may churn up.

...Jim Thompson

Show us.

See attachment. Sorry that Larkin is incapable of understanding the
basic behavior of _any_ inductance.

...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)

No amount of bloviation will cover your ignorance... wiring out to a
solenoid or relay before the catch diode will give you grief.

No matter how many times you bloviate.

...Jim Thompson

Using your idiotic simulation, I suppose so. Good thing I don't use
your idiotic simulations.

25 kilovolts! Hilarious! I wish I could make a 25 kilovolt boost
conveter from a 2N7000!



--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

On Mon, 18 Nov 2013 13:49:57 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 14:25:27 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 13:20:14 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 12:25:28 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 10:30:05 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 11:14:39 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 09:34:16 -0800, John Larkin
m wrote:

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
m wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART. com wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson


Whenever "Thompson" and "inductance" show up in the same post, amusement is sure
to follow.

Wiring inductance _between_device_and_catch_diode_ can cause voltage
spikes, depending on device turn-off speed... irrespective of what
smug-ass comments Larkin may churn up.

...Jim Thompson

Show us.

See attachment. Sorry that Larkin is incapable of understanding the
basic behavior of _any_ inductance.

...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)

No amount of bloviation will cover your ignorance... wiring out to a
solenoid or relay before the catch diode will give you grief.

No matter how many times you bloviate.

...Jim Thompson

Using your idiotic simulation, I suppose so. Good thing I don't use
your idiotic simulations.

25 kilovolts! Hilarious! I wish I could make a 25 kilovolt boost
conveter from a 2N7000!

It was to make my point... after all I did say, "Wiring inductance
_between_device_and_catch_diode_ can cause voltage spikes, depending
on device TURN-OFF SPEED... "

Slower times and less inductance will, of course, produce a smaller
spike... but there WILL STILL BE A SPIKE. And CDG of a power FET will
help slow things down... perhaps enough that the dwell time in the
gate charge plateau region will slowly kill you instead.

Sometimes I feel sorry for you, being manic-depressive has got to be a
burden on an otherwise (allegedly) productive person.

But then that other part of your personality springs forth, you know
the part I mean, the PLUPERFECT ASSHOLE SIDE. Then I lose my
sympathy, and rank you right up there in that class of pompous
ignorance alongside Phil Allison and Bill Slowman.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)

No amount of bloviation will cover your ignorance... wiring out to a
solenoid or relay before the catch diode will give you grief.

No matter how many times you bloviate.

...Jim Thompson

Using your idiotic simulation, I suppose so. Good thing I don't use
your idiotic simulations.

25 kilovolts! Hilarious! I wish I could make a 25 kilovolt boost
conveter from a 2N7000!

It was to make my point... after all I did say, "Wiring inductance
_between_device_and_catch_diode_ can cause voltage spikes, depending
on device TURN-OFF SPEED... "

Slower times and less inductance will, of course, produce a smaller
spike... but there WILL STILL BE A SPIKE. And CDG of a power FET will
help slow things down... perhaps enough that the dwell time in the
gate charge plateau region will slowly kill you instead.

Sometimes I feel sorry for you, being manic-depressive has got to be a
burden on an otherwise (allegedly) productive person.

But then that other part of your personality springs forth, you know
the part I mean, the PLUPERFECT ASSHOLE SIDE. Then I lose my
sympathy, and rank you right up there in that class of pompous
ignorance alongside Phil Allison and Bill Slowman.

...Jim Thompson

Boys, I don't mind a little disagreement, but Jim!
Putting anyone in the same category as Phil Allison,
shame, shame on you, that's a low blow.
Mikek

On Mon, 18 Nov 2013 17:47:13 -0600, amdx wrote:


...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)

No amount of bloviation will cover your ignorance... wiring out to a
solenoid or relay before the catch diode will give you grief.

No matter how many times you bloviate.

...Jim Thompson

Using your idiotic simulation, I suppose so. Good thing I don't use
your idiotic simulations.

25 kilovolts! Hilarious! I wish I could make a 25 kilovolt boost
conveter from a 2N7000!

It was to make my point... after all I did say, "Wiring inductance
_between_device_and_catch_diode_ can cause voltage spikes, depending
on device TURN-OFF SPEED... "

Slower times and less inductance will, of course, produce a smaller
spike... but there WILL STILL BE A SPIKE. And CDG of a power FET will
help slow things down... perhaps enough that the dwell time in the
gate charge plateau region will slowly kill you instead.

Sometimes I feel sorry for you, being manic-depressive has got to be a
burden on an otherwise (allegedly) productive person.

But then that other part of your personality springs forth, you know
the part I mean, the PLUPERFECT ASSHOLE SIDE. Then I lose my
sympathy, and rank you right up there in that class of pompous
ignorance alongside Phil Allison and Bill Slowman.

...Jim Thompson

Boys, I don't mind a little disagreement, but Jim!
Putting anyone in the same category as Phil Allison,
shame, shame on you, that's a low blow.
Mikek

I'm sorry! I besmirched Allison and Slowman :-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

"amdx" wrote in message
...
Boys, I don't mind a little disagreement, but Jim!
Putting anyone in the same category as Phil Allison,
shame, shame on you, that's a low blow.

Actually, when I read the first post of this latest series, I could've
sworn I was reading one of them. That distinct combination of arrogance
and ignorance.

Both John and Jim are equally childish as Phil.

Tim

--
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

On Mon, 18 Nov 2013 17:47:13 -0600, amdx wrote:


...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)

No amount of bloviation will cover your ignorance... wiring out to a
solenoid or relay before the catch diode will give you grief.

No matter how many times you bloviate.

...Jim Thompson

Using your idiotic simulation, I suppose so. Good thing I don't use
your idiotic simulations.

25 kilovolts! Hilarious! I wish I could make a 25 kilovolt boost
conveter from a 2N7000!

It was to make my point... after all I did say, "Wiring inductance
_between_device_and_catch_diode_ can cause voltage spikes, depending
on device TURN-OFF SPEED... "

Slower times and less inductance will, of course, produce a smaller
spike... but there WILL STILL BE A SPIKE. And CDG of a power FET will
help slow things down... perhaps enough that the dwell time in the
gate charge plateau region will slowly kill you instead.

Sometimes I feel sorry for you, being manic-depressive has got to be a
burden on an otherwise (allegedly) productive person.

But then that other part of your personality springs forth, you know
the part I mean, the PLUPERFECT ASSHOLE SIDE. Then I lose my
sympathy, and rank you right up there in that class of pompous
ignorance alongside Phil Allison and Bill Slowman.

...Jim Thompson

Boys, I don't mind a little disagreement, but Jim!
Putting anyone in the same category as Phil Allison,
shame, shame on you, that's a low blow.
Mikek


He gets abusive every time he figures out that he's wrong.

A PCB trace, or a wire, isn't an inductor: it's a transmission line
with some Zo. The drain voltage won't fly up more than Id*Zo, and will
fly up much less for practical cases.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

On Mon, 18 Nov 2013 18:34:01 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 17:47:13 -0600, amdx wrote:


...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)

No amount of bloviation will cover your ignorance... wiring out to a
solenoid or relay before the catch diode will give you grief.

No matter how many times you bloviate.

...Jim Thompson

Using your idiotic simulation, I suppose so. Good thing I don't use
your idiotic simulations.

25 kilovolts! Hilarious! I wish I could make a 25 kilovolt boost
conveter from a 2N7000!

It was to make my point... after all I did say, "Wiring inductance
_between_device_and_catch_diode_ can cause voltage spikes, depending
on device TURN-OFF SPEED... "

Slower times and less inductance will, of course, produce a smaller
spike... but there WILL STILL BE A SPIKE. And CDG of a power FET will
help slow things down... perhaps enough that the dwell time in the
gate charge plateau region will slowly kill you instead.

Sometimes I feel sorry for you, being manic-depressive has got to be a
burden on an otherwise (allegedly) productive person.

But then that other part of your personality springs forth, you know
the part I mean, the PLUPERFECT ASSHOLE SIDE. Then I lose my
sympathy, and rank you right up there in that class of pompous
ignorance alongside Phil Allison and Bill Slowman.

...Jim Thompson

Boys, I don't mind a little disagreement, but Jim!
Putting anyone in the same category as Phil Allison,
shame, shame on you, that's a low blow.
Mikek


He gets abusive every time he figures out that he's wrong.

A PCB trace, or a wire, isn't an inductor: it's a transmission line
with some Zo. The drain voltage won't fly up more than Id*Zo, and will
fly up much less for practical cases.

Only if it's over a ground plane. Dummy.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Mon, 18 Nov 2013 20:02:44 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 18:34:01 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 17:47:13 -0600, amdx wrote:


...Jim Thompson

Moron. A PCB trace, or a wire, isn't an inductor, it's a transmission
line. And a mosfet isn't an ideal switch.

According to your model, every mosfet always blows up from its own
wirebond inductance! Or from any drain trace, even if the load is
resistive!

(Thompson + inductors) dependably = (stupidity)

No amount of bloviation will cover your ignorance... wiring out to a
solenoid or relay before the catch diode will give you grief.

No matter how many times you bloviate.

...Jim Thompson

Using your idiotic simulation, I suppose so. Good thing I don't use
your idiotic simulations.

25 kilovolts! Hilarious! I wish I could make a 25 kilovolt boost
conveter from a 2N7000!

It was to make my point... after all I did say, "Wiring inductance
_between_device_and_catch_diode_ can cause voltage spikes, depending
on device TURN-OFF SPEED... "

Slower times and less inductance will, of course, produce a smaller
spike... but there WILL STILL BE A SPIKE. And CDG of a power FET will
help slow things down... perhaps enough that the dwell time in the
gate charge plateau region will slowly kill you instead.

Sometimes I feel sorry for you, being manic-depressive has got to be a
burden on an otherwise (allegedly) productive person.

But then that other part of your personality springs forth, you know
the part I mean, the PLUPERFECT ASSHOLE SIDE. Then I lose my
sympathy, and rank you right up there in that class of pompous
ignorance alongside Phil Allison and Bill Slowman.

...Jim Thompson

Boys, I don't mind a little disagreement, but Jim!
Putting anyone in the same category as Phil Allison,
shame, shame on you, that's a low blow.
Mikek


He gets abusive every time he figures out that he's wrong.

A PCB trace, or a wire, isn't an inductor: it's a transmission line
with some Zo. The drain voltage won't fly up more than Id*Zo, and will
fly up much less for practical cases.

Only if it's over a ground plane. Dummy.

...Jim Thompson

A trace or wire not "over a ground plane" has infinite Zo? It's a pure
inductance?

Gosh, Thompson teaches us something new every day. Generally wrong.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

"John Larkin" wrote in message
...
He gets abusive every time he figures out that he's wrong.

A PCB trace, or a wire, isn't an inductor: it's a transmission line
with some Zo. The drain voltage won't fly up more than Id*Zo, and will
fly up much less for practical cases.

So let's see how often you specify routed traces by inductance rather than
impedance and length in power circuits. Hmm? Oh, but that would defeat
your argument, so you won't tell. How convenient.

At 1/4 lamba:
Transmission line with Zo Z: inductive
Transmission line with Zo Z: capacitive

Independent of frequency (aside from Xc / Xl dependent on F).

Given the broadband nature of the relay circuit, overshoot will be
something, whether tranmission line or lumped equivalent. Obviously not
25kV, obviously not even over Vds(max), whatever that happens to be. But
consider a trace, to a relay, laid by someone without understanding of
high speed action, and probably not using a ground plane. Zo will
probably be in the 300 ohm range. Spike to avalanche? Easy.

Now shut the **** up, both of you. You're a disgrace to the internet.

Tim

--
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

On Tue, 19 Nov 2013 00:00:08 -0600, "Tim Williams"
wrote:

"John Larkin" wrote in message
.. .
He gets abusive every time he figures out that he's wrong.

A PCB trace, or a wire, isn't an inductor: it's a transmission line
with some Zo. The drain voltage won't fly up more than Id*Zo, and will
fly up much less for practical cases.

So let's see how often you specify routed traces by inductance rather than
impedance and length in power circuits. Hmm? Oh, but that would defeat
your argument, so you won't tell. How convenient.

At 1/4 lamba:
Transmission line with Zo Z: inductive
Transmission line with Zo Z: capacitive

Independent of frequency (aside from Xc / Xl dependent on F).

Given the broadband nature of the relay circuit, overshoot will be
something, whether tranmission line or lumped equivalent. Obviously not
25kV, obviously not even over Vds(max), whatever that happens to be. But
consider a trace, to a relay, laid by someone without understanding of
high speed action, and probably not using a ground plane. Zo will
probably be in the 300 ohm range. Spike to avalanche? Easy.

Now shut the **** up, both of you. You're a disgrace to the internet.

You're not making any more sense than Thompson.

The issue was, with a mosfet driving a relay coil, whether the clamp diode is
located at the coil or at the drain of the mosfet. I've heard people insist that
it must be at the coil, and Jim insists it must be at the fet drain. I think it
doesn't matter.

The case in point, that started this, was a 2N7000 driving a clamped 12-volt
relay coil at 30 ma, on a PC board. Jim thinks the inductance of the trace can
blow the fet. He posted a preposterous simulation to prove it.

If the trace were very long, and was 300 ohm Zo (both unlikely) the overshoot
from the trace would be 9 volts max, less in real life.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

In article ,
says...

On Mon, 18 Nov 2013 12:25:28 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 10:30:05 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 11:14:39 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 09:34:16 -0800, John Larkin
wrote:

On Mon, 18 Nov 2013 09:05:54 -0700, Jim Thompson
wrote:

On Mon, 18 Nov 2013 06:59:03 -0800, John Larkin
wrote:

On Thu, 14 Nov 2013 08:13:54 -0700, Jim Thompson
wrote:

On Wed, 13 Nov 2013 19:30:07 -0800, John Larkin
wrote:

On Mon, 11 Nov 2013 10:49:05 -0600, "Tim Williams"
wrote:

Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

Why? It will clamp a flyback overshoot wherever it is in the circuit.

If the wiring from FET to coil is significantly inductive, then what?

...Jim Thompson


Since you can't think this through, you'll have to Spice it.

No. It's _you_ who'll have to LTspice it... and you'll get it wrong
:-}

...Jim Thompson



Having fun, John?

Jamie