Author Topic: ESD Discharge Simulator  (Read 3113 times)

Mr Eastwood

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ESD Discharge Simulator
« on: July 22, 2014, 09:50:29 AM »
Here's a pic of something I picked up from Ebay recently;  it discharges 1kv at a level that simulates a standard human body model static discharge.  In the picture I used one of those pink anti-static bags for a quick test of something that offers bad ESD protection;  the LEDs on the module inside the bag show how much voltage gets through, and in this case this type of bag lets  > 300 volts through to whatever is inside.   I'll do a peek-inside when I get chance,  if anyone is interested.
« Last Edit: July 22, 2014, 09:52:10 AM by Mr Eastwood »
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MJLorton

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Re: ESD Discharge Simulator
« Reply #1 on: July 22, 2014, 02:24:13 PM »
Aaah yes...keen to see the insides and the results of other bags / materials.
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Mr Eastwood

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Re: ESD Discharge Simulator
« Reply #2 on: January 10, 2016, 07:09:03 PM »
As promised some peak-inside images;  for some reason they seemed to find it necessary to hide the relay types by scrubbing off the markings on the discharge PCB.


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SeanB

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Re: ESD Discharge Simulator
« Reply #3 on: January 11, 2016, 11:51:31 AM »
Yes, so difficult to figure out the relay types there.... RL1 is a double pole double throw Siemens relay, do not know the coil voltage but likely a 24VDC version, as those are cheap and common, and 35V rating for C2 says it is likely that. Also is rated for 2kV withstand between contacts and coil.. Easy enough to measure, look at voltage rating of . RL2 is a mercury wetted high voltage reed relay,  as that is the spec in the standard for the relay, so you get a fast rise pulse out of the 470pF 1500V capacitor to simulate the human touch model. 330R resistor is the emulated body resistance.

Charges the 47n capacitor to a high voltage, then uses RL1 to discharge it when power is off, via the 2 series 10M high voltage resistors, as well as to connect it to charge the 470p capacitor via the one 10M resistor. The reed relay then pulses to simulate a touch. Would be nice to see the bottom of the board to reverse engineer the circuit.

Detector is easy, the CA5260 is a CMOS input opamp, so it is arranged there as a simple flash converter, using a ladder of resistors to sample the pulse input, and the 74HC279 latches hold the maximum voltage from the converter to display.

http://www.intersil.com/content/dam/Intersil/documents/ca52/ca5260-a.pdf

Mr Eastwood

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Re: ESD Discharge Simulator
« Reply #4 on: January 13, 2016, 07:30:15 AM »
Thanks Sean!  after reading your comment I thought I'd have a go at reversing it,  so - here's some more info..

I think it basically works by charging up C5/C6 through one of the 10M resistors; once you press the test button it delays the HV switching action of RL2 using a RC with C3,  the delay gives the contacts on RL1 time to settle and route the HV charge from C5/C6 to RL2 and out to the positive test lead;  then once C5/C6 have discharged across the test material and you release the test button RL1 then connects the HV positive test lead to ground through the other 10M resistor - this I think is a safety feature in case there is still any HV potential across the test leads which might shock the operator.

Something like...

« Last Edit: January 13, 2016, 12:19:26 PM by Mr Eastwood »
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