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[SOLVED] Relay Problem: After on and off few times, the relay stuck/jam in the on stage.

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ben8118

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Dear all,

I'm doing home automation project which is turn on or off the house light.

I'm using relay to turn on and turn off the Fluorescent light which is 240VAC.
I'm facing a problem which after a few time turn on and off the light (in fast) the relay will jam (jam on the 'on/nc' stage, unable to turn off the relay). Every time I turn on or off the light, will hear spark sound.

I have parallel 1K resistor and 0.22uf capacitor with the relay. The problem still occur.
I change the relay amps from 5A to 16A. The problem still remain.

May I know what is the problem? and how to solve the problem?

Thanks.
 

In my view realy jam is mostly a mechanical problem ....what you do you can see the magenet that is used to attaction of the contact close have proper spring tension or not....some time spring that is used have less tensions....

good luck
 

How to see does the relay
have proper spring tension? thanks.
 

See for that you need to open the relay .... generally there will contact plate which get moves down word and attaracted to the electromagnet that is power by your supply....check in this way first you donot power up the coil and see that plate is generally is stright....if not then make it stright....many times it is bended...thne you press the plate see that it come back to it's original posistion or not..... Try the above sequence even after giving and removing power to the coil

better to more the 240v contact from NO and NC contact while doing this test

Good luck
 

Thanks for reply, I don't think I can open the relay cause is seal tight.
Other than check relay, are there any thing I can do?
Thanks.
 

The spark sound you hear must be arcing inside the relay. The contacts get fused together.

Something in the circuit is trying to maintain current flow when the relay starts to open.

A coil is a likely culprit. It stores energy in a magnetic field when current flows. Then releases it as a hi voltage spike when the circuit is broken. The spike often becomes a spark when it can't find a path through conductive substances.

Does your fluorescent fixture have a ballast? That might be the cause. However if it were common for fluorescent ballasts to cause arcing in a switch, then it would be a well-known occurrence.

You also report hearing the snapping sound when you turn on the light. A coil would not be causing a spark at those times. So perhaps my suggestion is all wet.
 

Maybe you can test the capacitance of cap by digital meter.I guess the cap must be ruined.
 

this is contact welding. Due to the arc the contacts get welded each other and you can literally never bring it back to its original state.
Check the ratings of what you are switching as well as the relay contact rating
 
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    FvM

    FvM

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Thanks for the reply.

Would like to ask would it be the inrush current from the fluorescent lamp cause the relay jam on the 'on' stage or others problem cause it/
Thanks.
 

Are you using microcontroller for the project? As relay is changed with bigger one and problem remains the same, now the relay is less doubtful. If mcu is used,try filtering its dc supply by adding a capacitor close to power pins. This is chatter sound you hear. Relay chatter due to improper swithing, Use schimitt trigger in drving stage. If schematic is shown, it can be easy to locate the fault.
 

Would like to ask would it be the inrush current from the fluorescent lamp cause the relay jam on the 'on' stage or others problem cause it.
Click to expand...
I presume that the relay itself is stuck to on-state, not the controlling circuit? In other words, it remains "on", even after removing the power supply. Your post isn't very clear in this regard.

Contact welding can be caused by the inrush current of a PFC capacitor, which is used in some ballasts. A tiny relay may be also damaged by the switch-off arcing. In both cases, using a rugged relay with 10 or 15A rating and suitable design (sufficient large contacts) should help. Arcing can be also reduced by connecting a varistor across the contacts.
 
Last edited:

ALERTLINKS: I'm using microchip as the micro-controller. I not sure it is the relay cause the problem, cause I referring others people design. when I use the relay from the design it work fine. However when I use other relay it have problem.


FvM: Sorry for did not make it clear. I'm using the latching(bistable) relay, which give a pulse and it change stage, and it will remain to the previous stage when power cut off. How can I reduce the arcing from the relay?

Thanks for the reply.
 

Reduce resistance of paralell snubber circuit from 1K to 100 ohm.
when I use the relay from the design it work fine. However when I use other relay it have problem.
Click to expand...
Which are these two relays?
 

ben8118 said:
Would like to ask would it be the inrush current from the fluorescent lamp cause the relay jam on the 'on' stage or others problem cause it/
Thanks.
Click to expand...

Yes, It could be the inrush current.
The only way out is to rate the relay specification higher. about 1.5 or 2 times your rated load current.

Find some way to measure how much current is your load drawing
 

ALERTLINKS: I use the Schrack 040967002000 relay is working fine. However, this relay is no more continue. Need others relay to replace it.

cameo_2007: Do you have any idea how to measure the current from the fluorescent lamp?

Thanks.
 

ben8118 said:
ALERTLINKS:cameo_2007: Do you have any idea how to measure the current from the fluorescent lamp?

Thanks.
Click to expand...

Do you have a clamp meter? If so you can clamp it onto one of the mains wires going to the load.
Or an Ammeter (digital multimeter in current mode) should give you some measurements to analyse.
 

Dear cameo_2007,

I'm making 2 gang switch. The life wire go into the wall switch and output 2 light to control.

I have tested the current using Clamp Meter. The current show in the neutral line is 2.4A when in stable, the maximum current before the current stable is 3.4A.

The both output to the fluorescent lamp also show 1.3A.

Thank you.
 

You didn't exactly confirm, that it's a relay contact problem (welding or other kinds of damage). If so, you probably have to face the fact, that no suitable bistable relays are available for the intended application.
 

3.4A is not at all a big deal for a relay to handle. However as FvM said ,there are better device to use for such application.

I have used relays to switch lighting loads upto 20A.But later switched to contactors for better reliability.
Just open up or break it open to see whether the contacts are welded or not.

what is the relay rating?
 

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