12v transformer open circuit.

[Nick Thomas]

Hi,
I've got a simple downlighter installation which comprises 2 halogen bulbs mounted inside the wooden surround of a decorative fire place.
There is a simple one/off rocker switch (semi hidden) so that the lights can be turned on or off.

So, I have a transformer which supplies the 12v to the halogen bulbs (which are connected in series), and the rocker switch is simply used to break the circuit - and turns the lights off.

But,
There is a problem - the lights will turn off when I throw the rocker switch to the off position.
But, the lights don't come back on when I throw the rocker switch to the on position!!!

I believe this is something to do with open-circuit protection inside the transformer.

What am I doing wrong?
And, how can I fix this situation?
Do I need more than just an on/off switch?
Is the transformer the wrong type for this installation?
Anything else?

Any help appreciated.

Thanks

Nick

 

[tazz]

What output voltage is the transformer, if 12v the the lights should be wired in parallel, not series.

 

[Nick Thomas]

Yes, the transformer has 12V output.
Actually the lights came on a pre-made circuit (in series) which was made for that fire surround.
I have sourced the 12v transformer myself!
It looks like the bulbs are meant to be connected in series - so that means that I've got the wrong transformer then!!!!

What type/brand of transformer should I have got?


Thanks

Nick

 

[westward10]

If the transformer has a 12V output, the 12V lamps are in series you would only have 6V at each lamp. Did they used to work.

 

[telectrix]

or could be that you'e supplying AC when they want DC.

 

[westward10]

or could be that you'e supplying AC when they want DC.

Should work AC or DC shouldn't they?
Maybe one of the lamps is gone so neither work if they are in series.

 

[Darkwood]

Your switching the load side instead of the supply side of the TX, if it's electronic this can cause problems especially if you break the load side as it may shut down and would require the supply side to turn off then back on with load circuit closed.

As for the series/parallel talk, I suspect it is parallel but may look like its in series it these are indeed 12v lamps and work to full brightness.

 

[Nick Thomas]

Hi,
Thanks for the replies so far.

Yes, the rocker switch is switching the load side of the transformer.
The behaviour is exactly as described by 'darkwood' above.

Should I be switching the mains side of the transformer instead? I need to check the rocker switch but it didn't look big enough to be a mains switch. But, I will check.

Ta
Nick

 

[Darkwood]

It's just speculation on my part but try various switching options and see how it behaves, no all electronic Tx's have open circuit monitoring so it pretty much comes down to what is been used to give you 12volts to see if it may be the case its shutting down on open circuit.

 

[Lucien Nunes]

Please confirm whether the transformer is actually a wirewound transformer, or an 'electronic 'transformer. If the latter (as we presume) it is of course not just a transformer but a switched-mode power supply with more or less sophisticated monitoring electronics inside, that may or may not object to having the load circuit broken.

 

[dmxtothemax]

[QUOTE="Nick Thomas, post: 1206884,
Yes, the rocker switch is switching the load side of the transformer.
Should I be switching the mains side of the transformer instead?
Ta
Nick[/QUOTE]

For sure !
This is gunna trip the protection circuit for sure
Do not switch the load side.