### Author Topic: Power Glitch Detection Circuit  (Read 1352 times)

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#### gyachts

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##### Power Glitch Detection Circuit
« on: January 04, 2023, 05:49:23 pm »
I'm working on a project where I need to detect a 0v pulse on a power supply line as a signal for loading.
If the power supply line has no low voltage pulses then the circuit does nothing.
If there is a pulse in the line going to 0v or near 0v, I want to detect the pulse so that I can latch the gate of a n-fet, using the simplest circuit possible.
I was trying to use a detection circuit with a p-channel fet that would then switch the n-channel fet and latch it.
When the pulse is present it is about 320us wide and repeats about every 8.7ms.
The line voltage can be anywhere from 11v to 15v.

I've attached a wave form example of the signal on the line.

Any ideas or experience anyone can share would be appriciated.

Greg

#### Terry Bites

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##### Re: Power Glitch Detection Circuit
« Reply #1 on: January 04, 2023, 06:17:08 pm »
Use a 555 in bistable mode. Its negative edge triggered.

#### jwet

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##### Re: Power Glitch Detection Circuit
« Reply #2 on: January 05, 2023, 03:32:50 pm »
At these speeds, I think I would put the uP in the loop.  The problem with something that is just neg edge triggered only is that it would get tripped on each power down cycle.  The unique thing about your trigger is the negative edge is followed by a positive edge in your max pulse width.  You could detect the drop out with a comparator or logic gate, have this go to an interrupt and then have the uP watch for the rising edge in the right time window.  Is this doable?- I don't know what you mean by "load" signal.  If there's no uP, then I think some kind of more complex 555 type circuit or comparators with open collectors/open drains acting as monostables?  LM393.

#### berke

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##### Re: Power Glitch Detection Circuit
« Reply #3 on: January 05, 2023, 05:41:09 pm »
How about this.  You didn't really specify what kind of supply you have for the monitoring side so I assumed 3.3V.  Parts count 1x74HC132, 1 diode, two caps, 4 Rs.

#### Zero999

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##### Re: Power Glitch Detection Circuit
« Reply #4 on: January 05, 2023, 06:24:58 pm »
What voltage threshold do you want it to trigger on?

#### EggertEnjoyer123

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#### EggertEnjoyer123

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##### Re: Power Glitch Detection Circuit
« Reply #6 on: January 06, 2023, 07:52:22 am »

#### gyachts

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##### Re: Power Glitch Detection Circuit
« Reply #7 on: January 06, 2023, 04:00:05 pm »
Probably anything below 1-3 volts.

Greg

Smf