off Relay after 3 second Timer

Thread Starter

aghaarash

Joined Oct 11, 2011
4
Hi guys. I want a circuit for relay which can turn off the relay after 3 second and it doesn`t turn off the relay if we reset the circuit or what ever to fresh this 3 second. if no action take place in 3 second then it turns off the relay.

I really appreciate if some help me in this situation.
Regards
Arash
 

#12

Joined Nov 30, 2010
18,210
Power must be off for 3 seconds before the relay turns off, Right? Relay "on" persist? Which relay? Volts, current, ohms of coil?
 

maxthestork

Joined Oct 13, 2011
13
I think I can see a solution for your system using a 555 timer for the timing funcion and a latching relay like the Omron G6HK-2-DC5.

You would set the relay when you turn on the power with a one shot action like a push button or a one shot timer function (again from a 555).

A separate timing circuit from a 555 would handle the reset after 3 seconds. There is a section in the datasheet that describes a sequential timer on page 15 of the datasheet.

cheers
Peter
 

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Thread Starter

aghaarash

Joined Oct 11, 2011
4
dear peter

I need a circuit that start counting for 3 sec and if there is no action in 3 sec it turn off the relay but if any action take place in this time a timer restart and count again. but I dont think 555 can do this. if you think I am wrong please let me know.

Regards
Arash
 

KMoffett

Joined Dec 19, 2007
2,909
I think you need a "retriggerable monostable" flip-flop. What's "any action take place"?...a voltage change?...a switch closure?...??? Whether or not the circuit can directly drive a relay depends on the relay you are using. What voltage do you intend to use to power this circuit/relay?

Ken
 

tracecom

Joined Apr 16, 2010
3,944
Sounds like an easy job for a microcontroller such as the PICAXE 08M2 (less than $3.00). The programming software is free, but one needs a programming cable; a serial cable can be made, but a USB cable is about $30.

The AXE-021 is a project board that could be used; possibly the relay could be mounted on the board. http://www.phanderson.com/picaxe/
 

#12

Joined Nov 30, 2010
18,210
This can be done very simply in analog IF you tell what the load is. The only way to keep a load powered for 3 seconds after the 12 volts is off, is to store enough energy to power the load for 3 seconds.

What load?

You don't say.
 

VoodooMojo

Joined Nov 28, 2009
505
dare it be as simple as this or am I misreading the OP's request?


or perhaps we are to sense a load applied or removed from an external circuit?

and how exact does the 3 seconds have to be?






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