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Topic starter
2019-07-23 2:33 pm
Hey folks,
This is an idea that came tangentially from a question I had in another forum here on DBWS.
I thought it might be a good project to build a theft control device. I will use an accelerometer to detect the unauthorized movement of my car then use a relay to kill the engine before it gets out of the driveway.
The sketch and basic wiring is easy enough but with the accelerometer and the relay coil and the relay switch all be on a common power supply and a common ground, what can I do to 'protect' the Arduino from electrical assault. I thought maybe some diodes in strategic locations might help but I don't know what I don't know.
The image shows a basic block diagram of the project. Would there be any use of adding diodes in any of the locations marked by a blue arrow? Or anywhere else?
This topic was modified 5 years ago 2 times by logwagon
2019-07-23 3:01 pm
You could put a diode from the car power to your regulator to protect from reverse voltage. Then on the input side of the power from the car to your reg, a largish capacitor across GNC and 12+, and then a medium size on the output of the reg to the Arduino across GND and 5+. I would test out different sizes to see what works best.
Topic starter
2019-07-23 3:40 pm
Any sizes of diodes and caps for me to start with?
2019-07-23 4:03 pm
I would find a big fat rectifier diode with at least 2a and 24v. You could possibly use a Schottky, but am unsure of the power going through the car wires. Start with 1uf to 10uf cap in the car power side and .47uf on the input to the Arduino power. Ceramic if you have them. I just usually swap them out to see what works best with ripple.
Topic starter
2019-07-23 4:11 pm
I have a buck converter to use instead of a voltage regulator. That should deal with ripple?
2019-07-23 4:15 pm
You may be fine on that side, just have one in the 12v car side to try and smooth out surges from the alternator.