Static discharge

[Gusse]

I'm working on a project in which a hardwired input from the "real world" may be subject to a static discharge when it's originally connected to the PIC/circuit board. Has anyone worked through this in a safe manner? Even if I use and optoisolator, it would share the common power supply and thus could still cause a problem.

Any suggestions on buffering the input safely would be appreciated.

picster

Hi Picster,

To protect HW, use some ESD protection components (varistor, TVS, etc..) and then add some small serial resistor (~20-40 ohm) in series in front of all inputs you need to protect. Use low Vbr ESD components, ~7-14V are OK. It will ensure that residual voltage will not burn PIC input.

To protect SW, use timeout(s) in input fuction(s) to filter out disturbances. If input still get triggered due to ESD then make sure that SW will accept only reasonable input strings.

If you have any interrupts, make sure that INT sources have filtering and SW can recover even if INT was due to ESD disturbances.

What kind of application you are building? And to which kind of environment?

BR,
-Gusse-