Re-purposing fan control unit for a wardrobe light

[timsk3]

I've got a bathroom fan that I no longer need, which has a simple electronic circuit in it to keep the fan running for a variable length of time after the light is switched off.

The circuit seems to be just a potential divider, a full wave rectifier, a smoothing capacitor, and a simple timer using a potentiometer, a capacitor, and some NOR gates. It has 240V going in one end, and it powers the 240V fan at the other end.

Is there any reason why I can't remove this timer circuit and re-use it for a light in a wardrobe, so that the light will go off after a few minutes even if the door doesn't quite close properly or is left open?

 

[OwainDIYer]

yes, if the door doesn't close properly the light will stay on indefinately.

you want a circuit of the type used for stair lights where even if the trigger contact remains closed the light only stays on for a few minutes

I'm assuming you're intending to use a door contact switch.

If you just use a manual pushbutton then the fan timer will do what you require

 

[timsk3]

Thanks for the answer, and in fact you're right, I can't use this as I had planned. I actually already have the light installed in the wardrobe, but sometimes it does stay on for long periods because the door hasn't been closed properly. (OK, it's only about 4.5W of LED strips, but still, I'd rather it didn't stay on anyway).

I'd like the light to come on when the door opens, but then to switch off (say) 5 minutes later, even if the door stays open. (It may or may not turn off if the door is closed in less than 5 minutes; doesn't really matter). With the circuit from the fan though, it'd stay on the whole time the door was open, PLUS another 5 minutes after it's closed; so it'd be worse than at present!

So: "a circuit of the type used for stair lights" — do you have a link to a particular item? I don't think I've seen the kind of thing you're talking about. Thanks in advance.

 

[RF Lighting]

http://www.tlc-direct.co.uk/Main_In...gear_Index/CMD_Main/CMD_Controls_3/index.html

Not sure if it'd work with standard push to break jeani switches though or if you'd need to just pulse the timer to prevent it staying on constantly.

If not, RS do a multi function timer which will do exactly what you want.

 

[timsk3]

Ah, I see, thanks very much for the suggestion.

 

[JohnW2]

yes, if the door doesn't close properly the light will stay on indefinately.

True though it is, it's obviously nothing to do with the timer circuit - it would be equally true without the timer - i.e. if the light were simply switched on and off with the door switch, in the common arrangement.

Kind Regards, John.