ESD Generator - ESD Gun simulator

[AllTheGearNoIdea]

Does anyone know how the switching of the ESD is done on commercial ESD gun simulators.  I am looking to build something to recreate the human model for precompliance testing and want something more controllable than a grill starter.  I am assuming that they maybe use a  high voltage vacuum relay  but not sure how they achieve the very fast rise times.  I have had a look on eBay but these are very expensive. I would probably be looking at discharging up to 10kv from a 100pf door knob capacitors. 

Just wondered if anyone had opened one up and had a look inside etc.

Thanks regards a Chris

[capt bullshot]

To my (limited) knowledge, they use relays. A mercury wetted relay achieves fast enough rise time (faster than semiconductor switches anyway), then there's a defined impedance in series to shape the pulse.

[Leo Bodnar]

Why bother making one?
Keytek 2000 is cheap and available on eBay.  Most of its complexity is in pulse train generation using 1980's tech.
Here is its operating instructions and service manual: http://manuals.repeater-builder.com/te-files/KEYTEK/KEYTEK%2020XX%20Operating%20Instructions.pdf

If you are trying to save cost, get only the gun and make the driver yourself.  I think the HV cap is at the back of the gun and is replaceable (I have not used mine in years...)

Hg wetted relays risetime is into picoseconds, it is probably an overkill.  Standard ESD pulse has only about 1ns risetime.
Leo

[AllTheGearNoIdea]

Thanks that’s really useful especially the manual. I have had a look for one on eBay for a few months and all the working ones were still relatively expensive and had shipping on the top which was expensive for the U.K. But maybe if I keep looking I will get lucky. I do still want to have ago at building a simple homebrew version I know it won’t be traceable to the standard etc but I still think it would be better than the grill starter option.

Thanks again really useful.

Regards Chris

[Leo Bodnar]

You can borrow mine to play with if you want.

If you keep offering £200-£300 to sellers you will eventually get one.  Shipping is not that easy to tackle though.

Leo

[AllTheGearNoIdea]

Thanks Leo that’s a really kind offer. Let me see how I get on with my homebrew poor mans version but something I would be interested in looking at.

Best regards Chris

[AllTheGearNoIdea]

I went ahead and built my ESD gun it is unlikely to comply with any of the test standards but neither is a Piezo Grill starter or charged plastic rule with spark gap so I still think it still has some utility.  I found it an interesting little project and enjoyed the construction.  The build was about £50 in total the highest cost item was the high voltage relay at £35.

Link here if anyone wants to take a snoop
https://youtu.be/eJ4gi0EaJOs

[joeqsmith]

I wonder if you welded the contacts yet?   

I have some relays that were made by a company that was sold.  The new company created new documents for their products and the marketing people left out some key information that a designer would need.   When it comes to selecting a HV relay, we can't just look at the rated voltage, current and cycles..

Did you get lucky? 

[floobydust]

What do you use for a HV switch in your transient generator?

[AllTheGearNoIdea]

floobydust:  I have attatched the relay datasheet

Pickering
SoftCenter ® construction
zz Option of PCB or flying lead switch connections
zz Small size
zz Up to 10 kV stand-off, 7.5 kV switching
zz Long life
zz Fully encapsulate


joeqsmith:  I dont think I have damaged the contacts yet but  I cannot look at the discharge curve as I lack an CRO with the required 1Ghz bandwidth. But I have not noticed any difference in operation. Its not like I do very much testing its the kind of thing I take out the box one every three years hit something twelve times then back in the box.

Im not sure on the contact life the relay it rated at 3A but the expected discharge based on the voltage setting can easily exceed 30 Amp.  I am overdriving the contact rating at 8K but I put the gun into constant mode after 8KV so the contacts are closed. Perhaps given the fact the pulse should only be a few nano seconds means there is not enough time to damage the contacts and  total energy is very low.   If you have better ideas please jump in.

Thanks Regards Chris