# Arduino + Ardumoto : External power source

I have an Arduino and an ArduMoto. I want to use that to power 8V motors with a 17V battery (using PWM).

It says for the Ardumoto that the VIN used to power the motors is the VIN of the Arduino (limited at 12V). But there is on the Ardumoto a VIN input, with written on the side : VIN Max 18V.

I wonder if I can plug in a 17V battery on this, without a risk for the Arduino ?

No - dont use the VIN of the Arduino- it lacks power to power up that Ardumoto driver. Use the VIN on the Ardumoto labeled Max18V

The only thing that you will loose because of 1volt shortage is some torque and slightly faster battery depleting.. but its in an acceptable range any way.

The VIN on the arduino is only used to power the PIC and some other controllable devices especially the Serial Communications. Never connect any heavy loads or voltages to the Arduino. Thats the purpose of the Ardmoto.

Keep the power source of the Arduino and the Bridge separate ideally- or at least isoloted by another voltage regulator if you want ot use one battery pack.

• Since when have Arduinos used PICs? – Kellenjb Jun 9 '11 at 20:32
• I think you misread my question. By default, Ardumoto uses the VIN of the Arduino, this is not the 5V output of the Arduino, which means you can have heavy loads with that. But I'm wondering if the additional VIN +18V of the Ardumoto (there is the VIN of arduino too on the Ardumoto) will send the 18V back to the Arduino, and then potentially damage it. – Matthieu Napoli Jun 9 '11 at 22:28
• In short : there are 2 VIN on the Ardumoto, one of the Arduino, one that I don't know what it does really (the documentation don't talk about that) – Matthieu Napoli Jun 9 '11 at 22:29
• About this weird 18V VIN on the Ardumoto, in ended up bending the pin of the Ardumoto shield so that it wouldn't connect to the VIN of the Arduino. Now I'm able to have the Arduino power by 9V battery or USB, and power the motors (through the 18V VIN of the Ardumoto) with my 17V battery. Nice! Even though weird. Thanks again – Matthieu Napoli Aug 3 '11 at 18:06
• Can you post a picture if possible.. it hard to imagine what actually you did. Thanks :) – Piotr Kula Aug 4 '11 at 8:38