I m working on a project in which i m using relay to switch light bulbs. The problem i m facing is that for the first 4 to 5 times relay switches on and off properly but after some time it starts to back-effect the circuit, i m using IN4007 as the suppressor diode and BC548 with the 5 V relay. Do I need to use a different diode? Is there a possibility that my diode is not working properly and I need to change that.

 

it starts to back-effect the circuit,

What kind of, "back-effect"? Blanks the digital display? Resets the microprocessor? Dims the ceiling lights?

 

What kind of, "back-effect"? Blanks the digital display? Resets the microprocessor? Dims the ceiling lights?

arduino starts misbehaving and the bluetooth module which I m using got disconnected.

 

Do you suppression circuits across the inductive load as well as the relay coil?

 

Do you suppression circuits across the inductive load as well as the relay coil?

sorry but I m not using any inductive load . I m simply using relay to control a light bulb. Sometimes its working and sometimes not.

 

Inrush current. Add capacitors to supply current to the light bulb(s) in the first moment of start-up.

 

Inrush current. Add capacitors to supply current to the light bulb(s) in the first moment of start-up.

Capacitor across the diode? Sorry, Can you please send me the schematic because I m not able to understand.

 

Capacitor across the diode?

Does the diode provide current to the light bulb?
No. The relay does.
Add capacitance to the power supply where it connects to the relay contacts so the start current of the light bulb doesn't load down the power supply.

 

Does the diode provide current to the light bulb?
No. The relay does.
Add capacitance to the power supply where it connects to the relay contacts so the start current of the light bulb doesn't load down the power supply.

which capacitor i should use and of which value? how can I connect a capacitor to this circuit?

 

One better way might be zero cross switching of the AC with a SSR.
Using a 2n7000, MOC3162 and a triacs, 3 of each.
Eliminates the ULN2003, and the relays.
BTW, the ULN has internal diodes so the 1n4007 are superfluous.
Max.

 

which capacitor i should use and of which value? how can I connect a capacitor to this circuit?

Now that you have provided some information, Max has a better idea.
Until that drawing in post #9 everybody was guessing.
Take a lesson. Provide enough information so we don't have to guess.

 

One thread is enough, so this thread will be closed.
The other thread as below:
Relay Backeffecting the circuit.