How control a Relay with PIC

[terka]

Hi

I want control a relay with PIC
I need some eschematic for this

Thank you

 

[smartsarath2003]

Have look at the previously discussed topic

 

[ASIC]

not to be rude, but there are billions of circuits available on the internet that does that. Maybe you could look in google first?


ASIC

 

[terka]

OK
sorry for my question, but I had contribute to this forum board too.

Bye

 

[rkodaira]

For small current relays and cheap circuit I use transistors to drive the relay from the PIC ports.
A NPN general transistor (BC547) can be used to drive up to 100mA coils. More than this you can use a darlington transistor or use a MOSFET (drivered by bipolar transistor).
Vcc
___!___
! !
_ !
1N4007 Λ Rly coil
!______!
!
!
C
PIC port >--Resistor----B NPN transistor
E
!
GND

Just remember to use 1N4007 diodes to Back Voltage generated by the coil.
The relay is activated by high logic level (4.7V in the PICs). The resistor is calculated:

R = (4.7V - Vbe)/Ib

Ib = Ic / transistor beta (Ib cannot be greater than 25mA)
Ic = current in the coil
Vcc must be at less the coil voltage + Vce saturation


The PIC I/O ports can source or drain up to 25 mA, so they can be connected directly to small reed relays (use the diodes reversed).

 

[Ace-X]

rkodaira, you should use tag "code" to preserve formatting of your picture, otherwise it is like mess.

As to relay control, small example with double-transistor is attached.

For many relay outputs I would suggest to use ULN2003 driver - it has Darlinghton and protection diode inside for 7 channels.