3904 NPN transistor to drive a relay

kurrodu said:

I am positive. I also interchanged the base and collector. The relay does not get triggered at all. SO I think I have the transistor wired properly.

Click to expand...

It's collector and emitter swapping that will give you marginal results, not collector and base.

Ron,

Now I realized that the circuit works fine as long as there is no load attached to the relay.

The load that I have is 240VAC 40Watt bulb.

I think there is noise that is being generated. So do you think there would be any protection circuit for this?

My friend asked me to look at weber circuit.

Thank You all

Finally, I have used an opto coupler MOC 3021 and a triac Bt139 that solved my problem.

Thank you all for the support.

I know this post is a few months old now BUT... I had a similar problem a while back - https://www.electro-tech-online.com/threads/driving-relays-using-pic-16f88.97988/

Opto coupling is definitely the way to go for reliability, although if this is not an option (IE too expensive) have a look at the above thread. Might give you some ideas.