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I want to use an Arduino (maybe Nano, maybe MEGA) in my motorcycle (a new KTM with lots of electronics). I checked my test circuit (with the MEGA) and it uses about 100mA (with 5V connected to the 5V pin).

Edit: the bike has a 12v battery and when it's on the generator pushes this up to about 14.3v.

For my first tests I used a 3 terminals DC/DC Regulator with output 5V for the Arduino power supply. If the ignition is on the Arduino works. As soon as I start the bike the Arduino restarts every couple of seconds.

Currently I used the BP5293 DC/DC Regulator because it has 2% precision. Currently I don't have any capacitors on the input or output terminals of that regulator.

I guess I have the following options:

a) Use the BP5293 and add capacitors on the input and/or output terminals. In the datasheet an output capacitor of about 10-330uF is recommended. For the input it recommends a capacitor but without any value given.

b) Use another regulator to 5V

c) Use a regulator to i.e. 7V and then connect that to the Arduino power input and let the Arduino do the filtering of the input.

What is the proper solution and what are suitable values for the capacitors?

I have 100nF ceramic capacitors and Low ESR electrolyte capacitors with 6.3V, 16V and 35V from 68uF up to 3300uF in stock. Obviously I could just try but I prefer to know how it should be done.

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  • Connect ceramic capacitor, recommended 10μF from the datasheet. I'd start with the input side, as the Arduino boards already have some capacitors on the board itself. Low ESR electrolytic, instead of ceramic, is most likely fine. Just make sure you have the correct polarity. I'd go for the 35V rating, just to be sure.
    – Gerben
    Apr 19, 2019 at 13:21
  • Your motorcycle battery is 6V, correct? You're probably having voltage drop problems. A capacitor on the input side of your power supply might help. You might also need a buck/boost power supply, which is able to increase or decrease the output voltage, since 6V too close to 5V for a linear regulator to handle.
    – Duncan C
    Apr 19, 2019 at 15:11
  • @DuncanC: I edited the question to show the bike has 12v. I didn't mention that because I think by now all bikes, even the smallest, use 12v. But if it would use 6v then you are obviously right about the consequences. Thanks
    – Edgar
    Apr 20, 2019 at 1:31

1 Answer 1

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The solution depend on what causes the reset.

It might be EMI interference on the RESET, in this case a stronger pull-up might help. The standard pull-up for nano is 1kohm which should be enough but if you use a clone the value might be higher.

If the reset comes from power drops then only a higher capacitor on the regulator input would not be enough since you also have other consumers on the 12V line that will suck the energy stored in the input capacitor.

Feed the capacitor and the regulator input through a diode, anode to 12v, cathode to capacitor/regulator. This will stop the energy stored in the capacitor to go back to the 12V line.

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