interface relay with pic16f877a.

[chandresha1]

hello friends.....
i am making water level controlling thorugh solenoid valve. i measure water level trough ultrasonic sensor & operate solenoid valve according to it. i drive solenoid valve(230v ac) trough relay.when i connect relay with my microcontroller it works fine & switching also. but when i connect this relays with valves. it operate two or three times & my microcontroller gets hanged. i interface this relays with uln2803 with diode for avoing back-emf. so what is the problem in that case? pls help.

 

[kak111]

If your circuit works perfect with relays, but not when valve solenoids are
connected , we can see the reason = solenoid.

1. Connecting solenoid drops 220Vac down
2. Opening solenoid relay makes voltage spike to 220Vac line
(3. Solenoid or power wire magnetic field ???? , if there is near low voltage wires)

Try following................

1. check voltage input to controller power supply
-are low voltages filtering capacitances big enough

2. add RC-supressor circuit parallel to solenoid coil

3. Low voltage wires are not very near and parallel with 220V and coil wires

Regards KAK

 

[chandresha1]

thanks kak. i have one another doubt. i m supplying my microcontroller with ac 230v with dc adaptor. i also connect my solenoid valves with the same extension board. so i think when valve operate it disturb the whole ac supply & maybe the supply to pic also gets disturbed. is it possible?

 

[kak111]

That is just what i mean.

Solenoid load is the cause of this fail.
It makes short load peak to the supply via 230V
or when relay contact opens, solenoid inductance send voltage spike to
supply.

KAK

 

[samson A.]

Good of you to have a diode across the relay, but you ve forgotten that even the solenoid valve actuator is also inductive. Did you not see the spark across the contact of the relay. Add a capacitor/varistor accros the no-pl contacts of the relay.




All under heaven

---------- Post added at 21:16 ---------- Previous post was at 21:09 ----------

Good of you to have a diode across the relay, but you ve forgotten that even the solenoid valve actuator is also inductive. Did you not see the spark across the contact of the relay. Add a capacitor/varistor accros the no-pl contacts of the relay.




All under heaven