I'm pretty nub when it comes to arduino, so if this is in the wrong forum, sorry.
Got a 12V pond water pump. I want to control it with my arduino, but I'm not sure if it's possible. The pump has 2 wires, one purple, one black.
If I hook it to the 5V rail on the arduino I can power it, but I'm not sure how I would go about turning it on, and off, as everything I see references devices with 3 wires. Can someone point me in the right direction? Do I need to use a relay?
You can't run a 12V motor off 5V. You need to supply it with 12V than use a transistor to boost the voltage up to 12V. Also you need to be able to switch the motor's current with the transistor so a relay is perhaps the simplest to start with.
http://www.thebox.myzen.co.uk/Workshop/Motors_1.html
It's actually a 5-12V pump. I can power it fine.
Going to read over what you sent, thanks.
It's actually a 5-12V pump.
Yes but you still can't run it from the arduino's 5v as you can't get enough power through the regulator or the USB lead. You need an external supply and you need to know the current it takes.
Ok, so I read that page you linked me. Think I understand it.
Guessing I can throw money at it, and buy a relay shield.
I'm thinking it will work like this.. The external power source connects to the relay shield, as does the pump. Then I would use my arduino to control a digital? output, which would be the pump.
Yes that's it. Don't forget to connect the ground of the 12V supply to the ground of the arduino as well:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html
You do not need a relay shield to do this. You need 10 pence transistor and a £2 5volt relay. Here is a random hit for "drive relay from ttl" that shows what you would need to build.