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.
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| 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.
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| Circuit Diagram Of Relay Drive By Microcontroller |
