Searching for a cheap high power relay

Question

i am building a robot but because its motor runs on a high amp power i cant simply use my rc boards as they always burn when the motor runs so i decided to make the rc board run a relay that controls the high power away from the boardthe rc uses 3v aa battery and the motor runs on a power supply of 12v dc (22amp)

Answer 1

How big is your robot?  That's a whole lot of current for the motor.  Radio Shack, in the US, has relays that can switch 20+ amperes.  There are other electronics parts shops in most good sized cities that will have them too.  I haven't seen a power relay that is driven by a 3 v power supply.  A perhaps better way would be a semiconductor switch with a power transistor, but that takes a bit more engineering.

Answer 2

I've looked through a lot of relay sites.

Your problem is that you don't have enough voltage to drive a relay of that current rating.  If you had at least 5v there are a lot of parts available.

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Here's an offbeat suggestion. Why not use two relays.  A low power one that can be activated by the 3v, it would need to switch less than 1A.. Then use that relay to switch the 12v supply to activate the power relay.  Unorthodox but it will work.

The suggestion to use transistors to switch is a valid one.  But unless you have the knowledge, you may end up frying some transistors.

Some sites to look at:

American Zettler,  Schrack(Tyco), Omron, and, Potter and Brumfield,

Here's a hint:  If you tell the company your a student working on a project, sometimes they'll give you the parts at cost.

Almost forgot, put a diode, such as a 1N4001 in parallel with each relay coil.  The end of the diode with the stripe should go to the relays' positive supply terminal.  

Relays being inductive create a transient voltage spike when turned off.  This diode acts as a snubber(gives the spike a place to go harmlessly).  It will save your circuitry  

Hope this helps, and good luck.