inputing to PIC 16F627A from Car wiring
Re: inputing to PIC 16F627A from Car wiring
A couple of things.<p>1. Make sure that the actual power supply to the Pic is as clean as possible, a choke in series in the post regulator stage or using a regulator specially designed for the car environment would help. Also ferrite rings around the power leads at the entry to the power supply would help.<p>2. Resistor in series to each pin used, will help overcurrent problems. Two diodes one with cathode to +v and one with anode to -v in series with each other, so that the cathode junction where the diode with anode to -v meats the anode of the other diode goes to the pic pin and also the signal line. Schottky diodes would be best or a very fast acting diode.<p>3. Enclose in an earthed metal box. Make sure power supply wiring and traces is larger than the other wires. Make sure the earth is a good earth. Twisting the signals wires may help. Possibly though not likely using a feed through diode(used in RF work) may help.<p>4. Real last resort, isolate the signal wires using an opto isolator.<p>One problem may also be the voltage on the MCLR pin is not rising fast enough and you are getting a reset condition. <p>Colin
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Re: inputing to PIC 16F627A from Car wiring
The caps are going help filter low frequency ripple - I doubt there is much of that in the car. Noise is another beast and it can get picked up well down stream of your powersupply. I would heed bodgy's suggestions. ferrite beads are your friends here.<p>Also, the signals coming into your PIC - are they 12V? You should use a divider to get them down to 5V if you aren't using opto isolation. <p>You might consider a low pass filter on your signal lines. Since noise often has a fairly high frequency (spikes with fast rise and fall), a well chosen pass frequency that is above your expected signal will help a lot.
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