Re: [PIC] Do you put a resistor in series with digital and analoginputs? by IVP .

> I'm just trying to make my projects as idiot-proof as possible :-) Nathan, It can take more than just a resistor, particularly for inputs. Current limiting is fine but you need also to look at voltage limiting Diodes (Zener, Schottky, TVS, etc) need to be used in some environments to soak up charge For example, a circuit with an electromechanical device, eg relay, solenoid, or capacitor shorting, can impose a spike when de-energising that is below Vss-0.6V. This can cause an input pin in the vicinity to latch up and fry. So it needs at least a Schottky diode (which has a lower Vf than the PIC's internal diodes) to conduct that spike. In this case, anode to Vss, cathode to pin. I learned that after losing several analogue pins and smoked a couple of PICs big time That's just one example. Noise and voltages come in many permutations. I've one board which needs much filtering because it sits right next to a spark plug, another is close to a 5W radio transmitter Mostly circuits don't need general over-protection, mostly, but there are times when you need to consider a specific circumstance eg Google for input pin protection Jo