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I have 6' of 24 gauge wire that will be carrying my voltage signal to the PIC's ADC - should I use a 1uf capacitor on the ADC input pin close to the chip?
Thanks!
hi,
I would add a 1K in series with the 6ft lead, close to the PIC's input pin.
I dont know what common/ground/0V line for the Vsource is from the remote [6ft end], but it would be advisable to use at least a twisted pair of wires.
Thats the Vsignal and PIC 0V.
If the 6ft wire is running close to other high current switching lines, I would consider a 5.1V or 5.6V zener from the PIC adc pin to 0V.
I am using a 2k resistor, but it is closer to the beginning of the 6' line. I will move it closer to the PIC.
I have 3 24 gauge wires going to the PIC, ADC wire, Ground and a 5v supply wire - all have been twisted together and placed in a vinyl jacket.
Is the Zener some type of overload protection in this case or does it block some unwanted interference?
I am using a 2k resistor, but it is closer to the beginning of the 6' line. I will move it closer to the PIC.
I have 3 24 gauge wires going to the PIC, ADC wire, Ground and a 5v supply wire - all have been twisted together and placed in a vinyl jacket.
Is the Zener some type of overload protection in this case or does it block some unwanted interference?
hi,
The PIC internal diodes are limited to about 20mA, I was concerned if the 6ft line picked up a low impedance source 'spike' the 5.1V zener would help to absorb the overvoltage current.
With a 2K resistor (as he's using) you would need 25V continuous input to pass 20mA.
If you've ever fitted a PIC in the socket backwards, you'll know that the protection diodes happily pass a LOT more than 20mA without damage
Problem is I'm not sure where the 6ft wire is routed, if its adjacent to HV switching circuits, it could pickup a lot more than 25V.
For the very small cost of a zener, I personally would fit it, again we dont know how critical it is that the PIC fails and the program stops.
Superflex, what is the actual project.?
Nigel, how could ever possibly believe I would insert a PIC backwards...