Hi, I am looking for a 12v 5a d.c power supply having 50ma output, to operate a relay coil and thus a 12v 5a motor. Please tell me where it is available and what is the cost? Or give me a circuit to make one.

 

Input voltage?
Is 5 Amps the MAX your motor will draw?
What country are you in? (helps find a source closer to you)

http://www.mpja.com/powersupply.asp

 

Let's see, you want a 12v, 5A DC power supply that has a 50mA output?

This doesn't seem to make sense. Do you mean that it needs to have something like a "voltage good" signal in order to operate the relay coil?

It's not good to operate a supply at 100% capacity. You should use a supply rated for more than your load.

Also, motors draw many times as much current when stalled (or starting from a stop) than they do when running at speed with no load. Is the 5A specification the stall current or the no-load current, or something else?

 

I thought he just wanted a power supply to use for powering both the relay and the motor..
Just an 12V 8A or 10A or whatever power supply. (5A+50mA+safety factor)

 

Possibly the cheapest way to get a supply would be to do the "ATX bench supply" modification on a computer supply that has a suitable 12v rating.

But, we don't know where our original poster is, so suggesting a supplier would be pointless.

 

Its a small customized motor which draws a current 5A max.
Also need to power a relay(load 50MA max.)
Please suggest the best power supply can be used.

 

check the link I posted above for different types but this 100W 12V will work just fine
http://www.mpja.com/prodinfo.asp?number=16013+PS