That does sound like the relay is releasing. The pun intended but the point is also true: things are moving inside to make the noise.

That does not mean the contacts have not welded together: I believe I've had some open frame relays that still "clicked" but I could see the contact lever stay in one connection.

So, what do you think I can do to prevent the relay's contact from being welded together?

 

Correct contact rating for the type of load
Resistive, inductive, AC or DC.
All these types of load place different demands and ratings to the contacts.
If this is the cause.
Max.

 

Correct contact rating for the type of load
Resistive, inductive, AC or DC.
All these types of load place different demands and ratings to the contacts.
If this is the cause.
Max.

My load is LCD TV or monitor can will use 240VAC. What type of load is it?

 

For what it's worth, I have experienced this exact behavior with a similar circuit. The relay would stick closed and only release on a rare occasions.

In my case, the problem was physical damage to the contacts due to overloading. We replaced the relay with a more appropriate model and everything was fine

 

AC Inductive.
Max.

 

AC Inductive.
Max.

So, what do you think I can do to solve this problem. Does putting a RC network will do the trick?

 

For what it's worth, I have experienced this exact behavior with a similar circuit. The relay would stick closed and only release on a rare occasions.

In my case, the problem was physical damage to the contacts due to overloading. We replaced the relay with a more appropriate model and everything was fine

Currently don't have the budget and space to change my components. I only can try to prevent it from happen. What do you suggest?

 

Currently don't have the budget and space to change my components. I only can try to prevent it from happen. What do you suggest?

Don't turn it on ?

 

Don't turn it on ?

I mean prevent the contact from being welded.. Or I should say, prevent the relay from being spoilt...

 

I may have missed some post's, but have you determined contact welding is the issue, without doubt?

If you ever get activated load with coil disconnected, then yes.

 

I may have missed some post's, but have you determined contact welding is the issue, without doubt?

+1

ahgan84: Did you ever stick a voltmeter on your circuit? I have not seen your data.

Without hard data all we have are guesses.

 

This particular relay may be at issue with a very tiny hold in voltage. Any leakage thru the transistor may be just enough to sometimes hold it on.

If this is the issue (and it does seem likely with a bipolar transistor), you could simply add a diode or two in series and be done with it.

It would be nice to hear what the meter reading is before though.

 

It occures to me one simple test not using any metering is to run the controller until the fault presents itself, then simply turn the controller off.

If it is a transistor leakage issue or similar, the TV will also turn off.

If it is a sticky relay then TV will remain on.

 

It occures to me one simple test not using any metering is to run the controller until the fault presents itself, then simply turn the controller off.

If it is a transistor leakage issue or similar, the TV will also turn off.

If it is a sticky relay then TV will remain on.

True, that eliminates all power to coil. Just as disconnecting it would.

 

some relays are subject to core magnetization. after use, the core is left magnetised and will hold in the armature. we had that problem in the pinball industry. a piece of tape on the pole piece of the relay stops that, by keeping the armature a little farther from the relay core.

 

some relays are subject to core magnetization. after use, the core is left magnetised and will hold in the armature. we had that problem in the pinball industry. a piece of tape on the pole piece of the relay stops that, by keeping the armature a little farther from the relay core.

To test that with a DC coil relay (as this is) you can just reverse the polarity on the coil momentarily ( a few ms). That should free it if it was stuck ON due to core magnetization.

 

The BEMF diode across the coil gives it a shot in reverse!
Max.

 

The BEMF diode across the coil gives it a shot in reverse!
Max.

The diode across the coil will reverses the voltage polarity but the current does not reverse.

So no shot is applied. It just drains out whatever energy was in there.

 

ahgan84
Have you done any trouble shooting yourself to fix this issue? Have you tried any of the suggestions presented to you in this thread? Have you made any voltage measurements to understand this problem? Is the only thing that you have done to correct your problem is to post comments in this thread?

Some very talented people are responding to your request for assistance on your problem. Please pay them respect by making and posting measurement data, implementing suggestions and posting results. If other responsibilities prevent you from working on this issue, a note stating such would be appreciated.

You did ask for assistance.