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Yocto and ESD protection - advice needed.

PostPosted: Jan 18th, '18, 15:18
by Oortone
Hi!

I noticed my Yocto and my x0x is both more sensitive to ESD than basically all my other gear. In the winter time when humidity is dropping these machines will sometimes reset when I touch their enclosure.

I had a discussion about this in a Swedish electronics forum where quite a few knowledgeable in electronics often participate. After having looked at the schematics many remarked that the ATmegas are poorly protected against ESD in these designs. Especially the Yocto. I got many tips but no real schematic suggestions.

They remarked the reset is not buffered properly, and that a capacitor of 100 nF between RESET and GND would be good.
Other ideas where better grounding, and TVS diodes. Also some people had concerns regarding the chrystal and that I should ground it’s metallic enclosure.

So now I wonder if others have had ESD problems with their Yocto and if someone has a successfully managed to make it less sensitive and in that case how this was done.

Here’s the discussion just in case, but it’s in Swedish:
http://elektronikforumet.com/forum/view ... =7&t=89602

Re: Yocto and ESD protection - advice needed.

PostPosted: Jan 21st, '18, 19:40
by helectromagneticus
Oortone wrote:Hi!

I noticed my Yocto and my x0x is both more sensitive to ESD than basically all my other gear. In the winter time when humidity is dropping these machines will sometimes reset when I touch their enclosure.

I had a discussion about this in a Swedish electronics forum where quite a few knowledgeable in electronics often participate. After having looked at the schematics many remarked that the ATmegas are poorly protected against ESD in these designs. Especially the Yocto. I got many tips but no real schematic suggestions.

They remarked the reset is not buffered properly, and that a capacitor of 100 nF between RESET and GND would be good.
Other ideas where better grounding, and TVS diodes. Also some people had concerns regarding the chrystal and that I should ground it’s metallic enclosure.

So now I wonder if others have had ESD problems with their Yocto and if someone has a successfully managed to make it less sensitive and in that case how this was done.

Here’s the discussion just in case, but it’s in Swedish:
http://elektronikforumet.com/forum/view ... =7&t=89602


Could you measure the electrical resistance between your chassis and the power supply ground? If the chassis isn't already connected, bonding the chassis to the power supply ground would help? Also, the digital and analog portions of the Yocto use separate grounds - I wonder if bonding them together with a resistor would help with your problem. This of course depends on how different the analog and digital grounds are...

Crystals usually perform better with a grounded chassis, yes. You can get them in 3-pin versions that have an explicit chassis-connected pin.

Interesting about the reset circuit - I'll have to take a look at that.

Re: Yocto and ESD protection - advice needed.

PostPosted: Jan 24th, '18, 16:00
by Oortone
Thanks for the advice.

I use an AC power adapter of wall wart kind. There's no power supply ground. Only two leads which I guess comes directly from the transformer.

I'll try the other ideas, thanks. How big resistance do you think I should use; 1M Ohm?