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

[ben8118]

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.

 

[ericgibbs]

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.

hi,
Most fluorescent lamps use inductors, so you could have high closing/opening currents at the relay contacts which in effect weld the relay contacts in the ON state.

Either use a Transzorb or Snubber across the contact pair.

 

[Reloadron]

Posting a circuit would help. Is the relay a DC coil relay and if yes do you have a flyback diode (snubber diode) like a 1N4000 series across the relay coil? What exactly is driving the relay? Next are the relay contacts physically arcing closed? Exactly where did you place the 1K and .22 uF cap? Across the contacts?

<EDIT> I see Eric is about.... </EDIT>

Ron

 

[ben8118]

ericgibbs: Thanks, will try to use Snubber .

Reloadron: I upload the circuit diagram tomorrow.

 

[Diver300]

Many florescent lights have a power factor correction capacitor. Others are run at high frequency and the mains is rectified and used to charge a big capacitor.

Either way, there is a huge turn-on surge.

Fit a surge-guard thermistor in series to limit the current.

I have had the same problem with a PIR turning on a florescent lamp. The surge-guard thermistor fixed the problem and has been running for years.

 

[andrewblog]

It sounds like a current peak problem. Note that fluorescent lamps have a long life, but they should work (as much as possible) in stable conditions. Otherwise you may use a led bulb, for example.

 

[KeepItSimpleStupid]

Are the relay contacts rated for AC?

 

[ben8118]

The relay contact rate is 240VAC, The relay name is schrack RT314A12

 

[4pyros]

The in rush current is welding the relay contacts closed.
You could try a motor contactor or a relay with silver contacts.

 

[ben8118]

Thanks for the suggestion, will try and see.

Would like to ask how to measure or determine the in rush current?

Thanks.

 

[4pyros]

Would like to ask how to measure or determine the in rush current?

Thats hard. Its vary fast. The specs on your light mite list it.

 

[KeepItSimpleStupid]

Big light bulb went off: That type of relay is supposed to work that way.

That relay is what's known as a "latching relay". It requires a momentary pulse and the relay turns on. It will STAY ON after power is removed.

To turn this relay OFF, you pulse the coil with the opposite polarity voltage. Again, it maintains the state when power is removed.

Thanks for the part number.