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On Delay Relay

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sohaib_a

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I have a relay that turns a switch on for an instant and then switches it off.But i want the switch to remain on for some time (about 40 seconds) and then switch off.I searched online and i got some hits but I am not sure what the devices do.What i figure is that the delay is only in the circuit i.e; the switch will turn on after a delay and then switch off.I have posted the links below.Is there any other type of circuit for device available this?Please let me know.

https://www.bakatronics.com/shop/item.aspx?itemid=466
**broken link removed**
https://www.bakatronics.com/shop/item.aspx?itemid=447
https://www.bakatronics.com/shop/category.aspx?catid=151&page=2&sortby=

also i found a circuit,but i haven't tried it yet

**broken link removed**
 
also i found a circuit,but i haven't tried it yet
**broken link removed**

hi,
This circuit is a monostable, when triggered, the output will remain high for the duration of the time delay cap/res, then switch low.

If you connected the output of the 555 to say. a transistor [which would drive the relay], that would give a timed relay operation.

EDIT:
added modified drawing.
 

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thanks for the reply...in your modification the switch triggers the relay...is it possible the other way around..i,e; the relay should trigger the switch and keep it closed for the desired time?
 
thanks for the reply...in your modification the switch triggers the relay...is it possible the other way around..i,e; the relay should trigger the switch and keep it closed for the desired time?

hi,
When you say should trigger the switch , what is this switch.?

Cant you use the relay contacts as the switch.?
 
well the switch is a mechanical push-button switch which controls a garage door.I have a an RFID Reader with a relay output(which is is part of an access control system) which is connected to this switch so that it opens the door.Is there is any other better and simpler way to do this.
 
well the switch is a mechanical push-button switch which controls a garage door.I have a an RFID Reader with a relay output(which is is part of an access control system) which is connected to this switch so that it opens the door.Is there is any other better and simpler way to do this.

hi,
The 555 is about as simple as it can be.

The RFID output triggers the 555 monostable which closes the relay, [for 40sec] the relay contact is connected across the mechanical switch.

Is this what you mean.?
 
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hi,
This circuit is a monostable, when triggered, the output will remain high for the duration of the time delay cap/res, then switch low.

If you connected the output of the 555 to say. a transistor [which would drive the relay], that would give a timed relay operation.

This sounds exactly like what I'm looking for in . Would you mind posting an updated drawing in that thread with resistor and cap values which will close the relay for 2 seconds and open it for 1 second?

Mez
 
Last edited:
This sounds exactly like what I'm looking for in . Would you mind posting an updated drawing in that thread with resistor and cap values which will close the relay for 2 seconds and open it for 1 second?

Mez

hi,
There is a modified dwg about 2 or 3 posts earlier.?

It will only energise the relay for the timing period.

Is this what you mean.?
 
I made a ckt like that before. With 3 seconds delay. I just use mosfet for the switch and an RC ckt for the delay. When I trigger the relay, it will switch on the switch and the relay will turn-off leaving the switch ON due to the delay provided by the RC circuit.

Here's the ckt that helps me:

The delay of this ckt is 2 mins. I just replace the value of resistor and capacitor at the lower left of the ckt with smaller one to make the delay 3 secs.

Hope this will help you.
 

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Simply put this ckt between your relay and your switch.

Connect the output of your relay to the S1 of the ckt and connect the output of the ckt to your switch.
 
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