[Motorcycle] Is extra capacitor needed for mini DC - DC buck converter?

Thread Starter


Joined Oct 10, 2021

I want to make a small LED monitor for my motorcycle, so I can read the engine's temp, oil temp etc... from there.
I am using Arduino Nano for this project and the power supply will be come from the motorcycle's battery.

When the engine is running, I guess the voltage from battery "is not" a pure DC voltage? Also, the power supply from the motorcycle is "dirty" & lot of "noise" and sometime will have voltage spikes? So the first step I think is to have a clean power supply.

Below is my schematic, and I would like to seek your advice, should I put some capacitors to the INPUT & OUTPUT side? to absorb the voltage spikes, clean the noise and protect my dc-dc buck converter? If yes, is C2, 10uF enough to absorb the voltage spikes? I assume C1, C3, 0.1uF can provide a smooth Vin, right?


My Mini DC-DC buck converter. It already have two ceramic capacitor on it.


Many thanks



Joined Jan 15, 2015
It won't hurt to add capacitance for filtering, not sure why the 1N4007 diode is in there but all it will do is drop about 0.65 to 0.7 volt. C2 will smooth the lower frequency noise while C3 filters the higher frequency noise. Since you are going with an Arduino NANO board and since you are already down converting the voltage you don't want to power the board using Vin. The Vin terminal is upstream of the board's onboard regulator so applying 5.0 Volts to Vin will not work. Since you have 5 Volts you apply it to the 5V pin. The Vin pin is for a 7 to 12 Volt input for the regulator to work.

Next since you are going to use a uC why not grab a display and look at things like Oil Temp, Oil Pressure, Battery Voltage and other engine parameters you may be interested in? Not saying using digital outs fro LEDs is a bad idea bit the NANO has a bunch of analog in and can easily drive a display.

Yes, you can use a higher voltage cap. :)



Joined Jan 23, 2018
Does the motorcycle have a battery? Many do, a few run on something often called a magneto, although it is more like an alternator off the ignition magneto. If there is a battery then that will be the point to start with the supply voltage source.

AND for filtering it is very useful to have a series inductance along with the shunt capacitors. The impedance of the series inductance rises with frequency and noise spike rise rate, and so that series inductor will keep a lot of the noise away from the shunt capacitors. The bypass capacitors form a voltage divider with the impedance of the noise source as the other resistor, while a series filter inductor presents a higher impedance to the noise current. Really,, both are needed.
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Joined Jan 15, 2015
I just caught in another forum:
My Mini DC-DC buck converter. It already have two ceramic capacitor on it. I'm not using 78xx is because the mini buck converter is small and no heat at all when convert 12v to 9v.
That being the case I wrongly assumed your buck converter had a 5 Volt output. My bad so you are fine using Vin.