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On/off automatic relay switch


stupidsalmon
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I have done this on various pecies of equipment, its cheap and faitly easy to do. If your not electrically minded the best way is to seek out a local Maplin store or find them online.

 

They do a series of projects and kits and amongst them is a timer circuit. It contains all you need, Vero Board, Timer IC Chip, Resistors, Plans, etc. All you need to provide is the connections, i.e. battery supply lead, on/off switch/ etc.

 

They work great and you can vary the amount of time the unit stays on. If the variable time is not long enough, changing one of the resisitors for a higher value will give a longer time range.

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Struth, to be honest it was years ago I last played around with them. Component wise I would have to dismantle the unti I built, to have a look. :/ Plans were thrown away, as they come with the kit.

 

From memory, it is very simple using a standard timer 8 Pin IC. This requires the usual power feed with resistors and then the a variable resistor for the time control, an on/off feed, and a transistor for the switching control. If your using it for a large motor, you'll need to use relay.

 

I'll have a look on the Maplin website for you and see if I can find the link. I beleive they do mail order. :lol:

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Ok no worries Axe,

Thanks for the link,

Would this one work okay: MK111 Adjustable Timer with Relay Output in conjunction with a motor i want to run at around 9V DC. Because it says its power supply is 12V DC would i need to put some kind of DC step up and step down transformers into the circuit so the motor doesn't work too hard??

Cheers

SS

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Its no good for what you want, the kit I linked to is what you need. Dont forget that the relay is there as a switch so you can run an independent 9v supply to be switched by the relay. Or you can use another relay switched by the first, if the motor draws a heavy current.

 

If its a light load you could use a step down transformer or a simple resistor with a bridging capacitor.

 

What is the application?

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The two circuits differ as one is designed to give a short output every so often with a variable time of up to 5 seconds. The second, the one I listed, is designed to give a permanent output, variable up to 15 minutes.

 

If the first circuit can be altered to provide a longer variable time then you can combine this with the second circuit to to give for example : 30seconds runtime every 2 minutes.

 

If i've understood the maplin site correctly.

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