Powering Arduino in Car instaation

Hi Guys,

I want to install an arduino in my car to suppement my car PC.

I got a few choices on how to power it:

  • 19 volt regulated power from an OPUS DC-DC power suppy
  • 5 volts reguated power from the same source
  • USB connector
  • Unregulated 12 volt power from the car which of course fluctuates a lot.

Is an unregulated power source from the car OK?

I am leaning towards the regulated 19 volts as it would power up in sync with the Car PC but I think that is at the top end of the specifications so I guess I need to step it down a bit. Is there a simple power circuit that would step the voltage down to 12 volts or so? I was not sure if a simpe votage divider woud suffice.

Thanks in anticipation.

If i was about to make that choice i would rather go a slightly different way.
There are USB to cigarette lighter adapters for a few bucks… you could strip one so you had a 5V regulated source and place it anywhere you want (if power cables run there) if you dont want to actually replace the cigarette lighter…

Car electrical systems are a really nasty environment: lots of annoying noise and voltage variations, but also potentially-lethal spikes.

If it’s convenient to run off the PC’s 5V supply, I’d do that, and rely on its protective circuitry.

If it’s not, I’d add a protective circuit to the power input.

Put a 1N4000-series diode and a resistor (about 10 Ohm 2W) in series with the power. Add a 27V-or-so Zener to ground to clip spikes, and a .1uF cap to filter some noise. If you don’t have a fat electrolytic on the power input of your Arduino, add it to the protection circuit.


Thanks. I have the Demilanove. there are 2 x 47 capacitors on it near the power supply. Does it have the fat capacitor? I see a few spare holes.

I will connect it to USB but I would like it to power it on when the Monitor powers up (which is before the PC). It is is driven by the 19 volts, so I was wondering if I could step it down to 12 volts easily.

If you want to run the Arduino off the 19V supply, you can use a voltage regulator like an LM7809 or LM7808 to step the voltage down and dissipate most of the waste heat. Depending on what’s connected to the Arduino, you might or might not need to put a heat sink on the regulator (I’d probably do it, since it only costs a quarter or so, but I tend to be overly-conservative about such things). The 19V supply should be clean enough that you won’t need to do all the noise- and spike-protection steps I mentioned earlier, though.


Thanks Ran, I had seen something like them in a catalog last night but not pulled the data sheet for it. 20 odd volts in and constant 12 volts out. The Opus PS cost me about $150 and is itself controlled by an Atmel MegaCPU, so it is pretty robust. As you say, filtering is not the issue.

I assume a motorcycle environment would also be noisy and spiky. I pretty much only have the arduino (probably an RBBB) and a few leds - what would I need to protect it?

Bill, Sure would be. Is your bike 6 or 12 volt?

I use an Opus DCA7 150 watt power supply from http://www.opussolutions.com in my car.

I see that they now have a separate 15 watt power supply that will output 5,7.5, 9 or 12 volts at 3 amps for USD $34 plus $5.00 for one in a case. It works from 6.5V to 30V input.

Might be a couple of dollars but you would only do it once! I will vouch for their support it is first rate, they even telephoned me from the US for installation support (I am in Australia!)

Other than that, be guided by what Ran said in the third post and maybe add an LM808/809 regulator as he said later.

im also planing to put a arduino in a car, an old one with some crazy noise from the ignition…

Z diode and big capacitor is clear, then i will put a 7805 with the capacitor´s and thats going straight into the arduino (and some other circuits)

is that enough, or can i put some sort off other filtering devices in front to keep the arduino save? :-/