Static

Feb 28, 2005 1 Replies
R

Hi



I hope there's someone here who can help me with this because I've never seen the like of it.



It's a PIC16C58B driving an LCD in a small, hand held ABS plastic case. There's a reverse printed perspex/lucite display cover held on with pressure sensitive adhesive. Inside it's all cmos to conserve power.



If you stroke the display cover with your finger you get spurious readings, someone just called to report the problem and I don't know how to fix it. There is nothing to ground it to, it runs of internal batteries, why should it care about static???



Help -angst- panic - hair tearing - etc :o(



Robin G Hewitt


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D

Hi Robin. I've had several bad experiences with ESD-sensitive electronics in the past. I've seen controllers which were so sensitive that the companies had to go to extreme means to deal with the problem

- ie, multiple lines of attack. Even small ESD charges are generally measured in the 1000's of volts, and can jump across spaces in the range of mm to cm, so the charge may be going around the sides to jump to your electronics. For this type of app, you might be able to re-route the charges away from your electronics. It might be possible to get a transparent conductive screen material. Alternatively, you might try putting some conductive material in the case to try and re-route the charges. Aluminized duct tape is good for this, and very easy to work with. This is the easy stuff to try. If it doesn't help, you may need to add spike suppressors to the electronics at multiple points, especially on the I/O lines. Transzorbs are good for this. SA5, P6KExx, etc.

- dan michaels

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