relay for air pump

Hi, I am trying to make my arduino controlling an air pump. The air pump is 6V and 4.5 A. It is a rechargable one. Today I just burnt the arduino... My circuit is done so that from a pressure sensor I get an analog read that controls another pin (digital pin), setting it high or low according to the data read. Then, I put a transistor where I have the cable of the digital pin (with high or low value). Today I just connected the air pump switch cables to the transistor and I got sparks and burning. What should I do? I think my arduino is destroyed... Thanks laura

Not all transistors can reliably switch high current applications. You should be using a transistor to switch a relay, which in turn switches the required pump or whatever.

Also make sure you put a reversed diode in between the transistor terminals to take care of the blow-back voltage from the relay.

As for the burnt board, try testing it separately. If you are lucky, you may have burned only the transistor.

Take a look at:-

http://www.thebox.myzen.co.uk/Workshop/Motors_1.html

We can't give you very much help with the vague description that you've given. Can you show us a circuit diagram (schematic)? Can you post your sketch source code?

Hi, thanks a lot for answering. if you could explain how to post a picture I could post them... thanks! if i click on image, it happnes like this:

OK, so paste the URL of your image in between those IMG tags.