Relay Driver Using Micro-controller

Relay Driver Circuit For Micro-controller

We can not directly drive the relay through micro-controller because the micro-controller gives only regulating pulse ( 0 or +5volt) , which is not capable and sufficient to drive the relay directly.

The relay coil operate at +12volt supply and it take approx 20-25 ma current. So the total power required by relay coil for energies or operate is,

Power = volt * current

= 12 * 0.020

= 240 mw

The micro controller does not provide sufficient current and voltage for this operation. It provide only a few mw power (which is only describe as signal).

Thus the second part is required for provide a sufficient power as the form of voltage and current as per requirement of relay coil or any other load.

Internal view of ULN2003

The ULN2003 is a monolithic high voltage and high current darling ton transistor arrays , which is specially design for relay driver or inductive load driver.

It consists of seven NPN transistor pair s that features high voltage and high current output with common cathode clamp diode for switching inductive loads. It capable for handling 500ma collector current of a single darling ton pair.

Circuit Diagram Of Relay Drive By Microcontroller