Simple relay switch - but how?

[daveguk]

Hi everyone!

I have a circuit I want to build and need your help. I have two circuits, both with lights in them. When the switch is pressed light 1 goes on, and the relay means light 2 also turns on. When the switch is released both lights go off. Easy.

What I want however is when the switch is released light 2 stays on for 60 seconds. I am stumped - is there a component that will allow this, if not can you point me to a similar circuit. I have tried searching with no luck.

Many thanks in advance.
Dave

**broken link removed**

 

[Diver300]

You need a time delay relay.

Bathroom fans often contain that sort of timer so they stay on after the light goes off.

 

[KMoffett]

You need a "delay-on-break" or "power-off-delay" relay/timer/switch.
A quick Google for commercial options:
http://www.amazon.com/Idec-RTE-B22-12V-Electronic-Timer-Single/dp/B000PJ8HXS
**broken link removed**
http://www.relayspec.com/catalogs/002300/4711.pdf
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Or are you more inclined to build an electronic circuit from scratch?


Ken

 

[daveguk]

Thanks so much for your replys - what a nice welcome to the forum. That was just the information I was after. I hadn't thought of the bathroom fan, I will most likely buy one and remove the timer delay relay from that. I can have a tinker and see how it works - go on and build a circuit if I need to.

Cheers!
Dave

 

[Willbe]

From Hosfelt, under "relays"

180 Second Delay $US 5.95
Mfg. - MIDTEX
Mfg.# - 711-180B115
115 VAC input, SPST
1-1/4" dia. x 2-1/8" H metal enclosure
5 amp @30 VDC/120 VAC contacts
Superior replacement for plug in timer.
Normally Closed
PN 45-598

and they probably have others suited to your app.

or else, if the timing need is not precise, get a relay with a high coil resistance and use a transistor and a 1000 µF capacitor to simulate a really large capacitor (apparent C = β[actual C]). A 12v relay drops out at ~9v.
This circuitry could get tricky.

 

[daveguk]

Thanks for all your responses guys. I have since found this schematic:

**broken link removed**

It is a nice easy circuit I can understand. I will be using the one on the right. The only limitation I can see is that the time constant RC used to hold 2N2222 in conduction will mean the circuit will only work if the trigger has been on long enough to charge the capacitor.

Therefore a pulse (or short trigger) at the 1N4002 anode will result in a short off delay, not the long one wanted. I will look into a solution for this.