I just designed a differential lock controller for 4 wheel drive vehicle, it worked great and the customer is very happy with it (after extensive testing by mechanical engineers thanks god :) ) it is actually going into production.
Just before I make my first production prototype I have few questions which I like your opinion.
1. I sense the position of 5 contacts with respect to ground either open (hi through pullup resistor) or short to ground, the sensors are approximately 3 meters away, they are working fine just connected directly to port pin of the microcontroller, do I need to use opto-couplers for these switches and contacts?
2. I sense the speed pulses from proximity sensor, I buffer the pulses and send them to interrupt pin directly, do I need to use optocoupler also after the buffer?
3. Do I need to use line filters to my signals on the microcontroller board?
4. I have a single chip microcontroller, do I need a solid ground plane, although my circuit lives in a grounded metal case with nice military connector?
5. Can I drive LEDs on the dashboard direct of the controller board using a driver transistor?
6. Looks like I have optocouplers on the brains, I thought we only use optocouplers to get red of ground noise in signals from different systems, in this case where I have switches and on off contacts do I need optocouplers at all or is there a cheaper alternative?
7. My circuit seems to work nicely without any of the above, I can't raise my cost up because I might risk losing the contract, any suggestions please?
Regards
Mahmood