Regarding reverse polarity. Arduino power source.

Forum 2005-2010 (read only) Hardware Interfacing
1

Okay, got two quite separate questions coming up.

  • I've got two transistors connected to the Arduino, which are used to power on the 6v motors from the 6v battery source. There problem here is, I can't go backwards, how should I reverse the polarity on the motors when I want to go backwards?

  • Since I've got two 6v battery "holders" I was wondering if it is possible to power the Arduino Duemilanove with 6v? Right now I'm using the USB port. I did see that the "Arduino playground" guide recommended 9v, but 6v would be a lot easier for me.
    Arduino Playground - 9VBatteryAdapter

2

The standard solution for reversing motors is an H-Bridge (google it).

The established wisdom is that its 7V minimum into the DC plug.

3

The established wisdom is that its 7V minimum into the DC plug.

Yeah pretty much but it depends on what you are doing with the arduino as to whether you can get away with it. The minimum is kinda stated as 7V due to the dropout on the regulator. Anything lower than that and you risk the regulator not supplying the chip with the 5V that it requires. I have used a 6v pack before and for most things you can get away with it but for some things, the ATmega chip needs 5v to do it properly.

Mowcius

4

The ATmega can take upto 5.5V max, so one possible method is to pass 6V supply through a rectifier diode to drop about 0.7V, thus becoming 5.3V

Wise to double check that fresh batteries aren't much higher than 6V though.

Incidentally 4 NiMH cells are about 5.4V--5.0V anyhow, which is in spec for the Arduino. 4 NiCd's will give about 4.8V which is OK too.