Can you power an Arduino with a car battery-spec sheet says yes??

I am real new to working with electronics and reading spec sheets, but it seems to me that you can hook an Arduino Uno directly to a car battery through Vin and Ground and it will be OK. And reading the specs on Sparkfun you can do the same with the Pro Micro by connecting to RAW and Ground.

So we are talking about 13v and maybe a little more coming off the car battery...

From the specs:
Input Voltage (recommended)
7-12V
Input Voltage (limit)
6-20V

Anybody have a definitive answer that this is OK?

Read the official specs

If they are not genuine they may not take that voltage input though

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Mark

If you read my email you would see I quoted the spec and it says the limit is 20v. A little over 13v is not 20v. As I mentioned I am new to electronics so don't how much stress this puts on the board.

Maybe if I explain my project it might help. I want to build something that is as small as possible, that goes on a motorcycle and that can drive a 3 watt LED. The LED will flash different rates depending on inputs. The electronics needs to go into the smallest possible waterproof box I can fit it into. The Light will be separate in a solid aluminum, waterproof holder. I want the light holder to be very small so it will contain just the LED and not other components.

I have built a prototype using a Pro Micro Arduino using a motorcycle battery running through a voltage regulator board, outputting 9V, attached to the RAW/GRN pins. The LED is being driven off the VIN pin through a 3v regulator chip controlled from one of the Arduino pins through a MOSFET. The LED draws something like .400ma.

I ran the prototype for about 2 hours last night without any heat issues so it appears to be working OK.

However the 9v voltage regulator board more that doubles the size of the whole project so would like to either power the board directly from the battery or find another solution that is a lot smaller.

Any ideas would be helpful.

Thanks

You have answered your own question by already quoting the specs then. A limit of 6 - 20V. If it fails due to the voltage input and it is within those specs you can claim on Arduino's warranty and get a new board.

They wouldn't quote those limits if they hadn't tested and were sure of reliability within those values. A battery being charged will not go over 15V - 99% use a max charge voltage 0f 14.7V for SLA. You are well within the quoted values

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Mark

Thanks MarkDerbyshire... being knew to all this I wasn't sure how to interpret "recommended" vs "limit".

If this is the main motorcycle battery, be aware that when being charged the voltage can spike significantly above 13V!

I think a real problem might not be the input voltage seen in isolation, but rather the heat dissipation required to get it down to 5V at whatever current is drawn.

It might be better to drop that voltage outside of the Arduino, but that's where we came in.

Tenorjazz:
I am real new to working with electronics and reading spec sheets, but it seems to me that you can hook an Arduino Uno directly to a car battery through Vin and Ground and it will be OK. And reading the specs on Sparkfun you can do the same with the Pro Micro by connecting to RAW and Ground.

So we are talking about 13v and maybe a little more coming off the car battery…

From the specs:
Input Voltage (recommended)
7-12V
Input Voltage (limit)
6-20V

Anybody have a definitive answer that this is OK?

You can run any Arduino board on 12 volts.

In an automotive or motorcycle application, I heartily suggest a circuit like this:

(click for full size)
12v_pwr_sply.jpg

The purpose of the parts is as follows:

The fuse - fire safety obviously
The diode - keeps large current drain spikes from getting to the Arduino and crashing it
The 1000 uF cap - ditto
The 7805 - provides nice clean stable 5 volts for the Arduino, and provides a LOT of electrical noise rejection
The 100 uF cap - keeps the 7805 stable - probably don’t even need it

The fuse, diode and large cap are ABSOLUTELY necessary to keep electrical noise out of the Arduino, which can crash the running software and even damage the AVR chip.

Hops this helps.

You could always hack a automotive cigarette lighter/USB convertor and get a decent 5Vdc for the Mini. They cost about $5 US, and after removing the case and connector for USB and lighter socket, are pretty small. Just solder some wires in and it's ready to use.

tinman13kup:
You could always hack a automotive cigarette lighter/USB convertor and get a decent 5Vdc for the Mini. They cost about $5 US, and after removing the case and connector for USB and lighter socket, are pretty small. Just solder some wires in and it's ready to use.

THAT is a good idea!

Tenorjazz:
If you read my email you would see I quoted the spec and it says the limit is 20v. A little over 13v is not 20v. As I mentioned I am new to electronics so don't how much stress this puts on the board.

Maybe if I explain my project it might help. I want to build something that is as small as possible, that goes on a motorcycle and that can drive a 3 watt LED. The LED will flash different rates depending on inputs. The electronics needs to go into the smallest possible waterproof box I can fit it into. The Light will be separate in a solid aluminum, waterproof holder. I want the light holder to be very small so it will contain just the LED and not other components.

I have built a prototype using a Pro Micro Arduino using a motorcycle battery running through a voltage regulator board, outputting 9V, attached to the RAW/GRN pins. The LED is being driven off the VIN pin through a 3v regulator chip controlled from one of the Arduino pins through a MOSFET. The LED draws something like .400ma.

I ran the prototype for about 2 hours last night without any heat issues so it appears to be working OK.

However the 9v voltage regulator board more that doubles the size of the whole project so would like to either power the board directly from the battery or find another solution that is a lot smaller.

Any ideas would be helpful.

Thanks

The basic problem is the inductive spikes from the starter motor armature. If ALL accessory circuits, including your Arduino are turned off while the starter motor is active, you are ok. That is why all light and accessory circuits on modern automobiles are off while the starter motor is operating.

Paul

Paul_KD7HB:
The basic problem is the inductive spikes from the starter motor armature. If ALL accessory circuits, including your Arduino are turned off while the starter motor is active, you are ok. That is why all light and accessory circuits on modern automobiles are off while the starter motor is operating.

Paul

The circuit I posted was one that I used many years ago when I built an all TTL digital clock for my car. In spite of capacitors, resistors and all kinds of filtering, starting the car crashed the clock every time.

Since at that time I didn't have an oscilloscope, I had no idea what the problem was.

I was talking about the problem with a buddy of mine and he took a sheet of paper and said "let's try to figure out what happens on the 12 volt line when the car is started".

The "graph" had a straight 12 volt line, a very short dip down to around 6 volts that rose up to about 8 volts and went up and down as the starter motor drew more and less current with each compression stroke, followed by a quick positive spike when the starter was disengaged.

I looked at and thought "I figured all of that EXCEPT the quick downward spike" and decided to try using a series diode to keep the negative spike from "draining" the input filter cap. It worked... the clock never crashed again.

If there's ANYTHING that's vitally important when connecting digital stuff to a car 12 volt system, it's that diode and a capacitor large enough to provide power for the duration of the spike.

With an oscilloscope (or a bit more thinking) I could have solved that problem a lot earlier....