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Relay interfacing

paddy

Sep 11, 2012
81
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Sep 11, 2012
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Hi,

Greetings of the day!!!!!

I have to interface relay with PIC 18F4520 micro controller.

Coil voltage of relay is 5V. So is it okay if I use common 5V supply for micro controller and relay coil or I need to use another supply for relay coil to get an isolation?

Please suggest.

Thanks
Paddy
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
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Nov 17, 2011
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13,700
You can use the same supply voltage.
you should add a simple driver between the µC and the relay for two reasons:
- current consumption of the coil
- flyback voltage from the coil at turn-off

The driver protects the µC.
 

paddy

Sep 11, 2012
81
Joined
Sep 11, 2012
Messages
81
Thanks a lot Harald Kapp for your kind reply.

I am using same circuit as suggested by you.

Thanks again.
 

dpenelob

Mar 27, 2013
15
Joined
Mar 27, 2013
Messages
15
Hi paddy,

if you had more than one relay to be controlled,
I might suggest using the ULN2003/ULN2803,
which already have integrated flyback diodes.

Best regards,
dpenelob
 
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