Can 12v 500ma transformer swithc 12v relay?

[saileshdewangan]

I am using 12v 500ma transformer in my 8051 project. I want to switch 12v relay using mcu. Is it possible to switch relay with 12v 500ma transformer. I am using voltage regulator ic LM7812.

or I have to use 15v 500ma transformer.

Thanks

Regards:

Sailesh Dewangan

 

[ahmad1954]

probably you should use 15v transformer because 7812 need about 1.25v for biasing and after the mcu and before relay you should boost the current to trigger the relay. for amplifying the current you can use a buffer with opamp.

 

[T3STY]

It does for sure, but you have to check the relay operating conditions. It has to be rated 12V 500mA (or less), otherwise the transformer won't be able to properly trigger it (7812 is OK up to 1A). Also, in most cases the PIC won't be able anyway to trigger the relay because of the low current flowing in pins (30mA max, usually), so you'll have to use a transistor to power the relay trigger. Check this scheme:
**broken link removed**