I have to mount some pushbuttons on a metal panel. So if the person's finger who is pushing the button is full of ESD, how do I protect the circuit?
I've seen pushbuttons who have an extra connection for earth ground. Is that connection meant to protect against ESD?
thanks, Mike
Give the current a shorter path to travel to ground than through your circuit- so it will spark to ground. Some series resistance wouldn't hurt either.
Yes.
Best regards, Spehro Pefhany
On 9 Sep 2003 11:21:22 -0700, snipped-for-privacy@yahoo.com (Mike V.) Gave us:
Get metal button hats that tie over to chassis, OR have the idiot discharge himself to the rack chassis BEFORE using the controls.
Older switches were usually AC, and metallic switch shells had to be grounded as a rule. In more modern years, yes, I'd have to say that ESD protection must be one reason they are provided in that fashion.
Buying shrouded pushbuttons works as well, as the shroud is metallic, and is touched before the switch.
Plastic switches should have some kV level of isolation to the operator from the circuit, so I can't imagine the case you mention where his discharge would actually make it to the switch terminals behind the panel.
Look carefully at the construction of the pushbutton.
Typically, the plastic part pushes a spring contact again a more fixed contact. If you arrange the circuit so that the movable contact is GROUNDED. The mounting hardware, of course, is already grounded.
This should keep the nasty electrostatic stuff away from the IC or whatever. You can add a little more protection by clamping diodes and resistive isolaton of the "fixed" contact.
That's usually just to provide another place to solder a ground wire. If your case, you can use it to bond the movable contact to the chassis or panel.
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