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Baby orangutan to control voltage to automotive gauge - jumping car wiped out program


I have built a project that uses the baby orangutan motor pins to send a voltage to operate the dash fuel gauge on my 1940 Ford. The orangutan is programmed to measure/calculate the variable resistor in the gas tank float mechanism in ohms (through the use of a voltage divider using Vcc as the reference voltage) then send the correct voltage to the dash fuel gauge. This all works fine and the gas gauge reads correctly. I might note that I use one of your voltage regulators (your #2861 - 9V output) to power the orangutan from the car’s 12 V electrical system. The problem I just had was that I had to have the car jumped when trying to leave a car show and after that the gauge read empty (basically a 0 V input). I bench tested the circuit and realized that the program had been erased or at least messed up and no longer sent a voltage to the fuel gauge. Reloading the program fixed the problem and all is working again.

Could this have been the result of a surge due to jumping the car? Any other possible causes? Any suggestions on how to avoid the problem in the future?




Hi, Burke.

I am not sure if the issue was caused by a voltage spike, but I imagine that a car is a pretty electrically noisy environment and that could be significantly worse when jumping it. You might consider adding TVS diodes and large decoupling capacitors to the input of the regulator and/or Baby Orangutan to help protect it from spikes or noise. If you haven’t already, you might also try asking what general protections people use on an automotive electronics forum.




Thanks for the help on this issue.

I tried to find info on how large “large decoupling capacitors” should be and found only info on small ripple from power supplies. One engineer said automotive applications can have surges of up to 60 V from the alternator. I think a TVS would handle the possible large surges coming from the car electrical system. But between the pololu voltage regulator and the baby o, what would you recommend for surge suppression or would it be unnecessary if the voltage from the car is kept below 36 V (the max voltage for the pololu regulator)?



We do not have much knowledge when it comes to automotive applications, so we cannot really give advice on what scale of capacitors or TVS diodes might be appropriate or if that would really be practical. That is why I thought an automotive electronics forum would be a better place to ask.