i am looking for a circuit which has the follwing oparation:

when i give voltage to this circuit (12 v dc), after a time (approximately 40sec-1min) this circuit
to give 12 volts dc to a relay (12v dc/ 230 volts). i want this time to be variable with a variable resistor.
the circuit i am looking for is a power-on delay circuit.
i have listen many ideas like cd4060, CD4541 lm555 but i have not a circuit. please help me and post a circuit here.
thanks

 

Come on it's not that hard really.

I'm in a good mood so I've done it for you but I won't give you the component values, you can calculate them for yourself.

Attached Images

On delay.GIF (2.4 KB, 72 views)

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You really are a sucker for a good cryin' jag

 

Hi Tzitzikas,

Try this one:

on1aag.

Attached Images

Delay circuit.GIF (9.9 KB, 63 views)

 

Here is the simplest circuit with 3 parts only. R2 is your relay that closes with delay and R1*C1 determines the delay, so if we simplify and disregard the input current to base, the delay would be proportional to R1.

I used two power sources for simulation but they can be merged into one.

Picture #1 is the schematic, picture #2 is the voltage over time graphs and ZIP contains LT spice schematic so you can play with it.

This circuit is just a hint. Massage it in the SPICE software and determine your values.

Attached Images

	power-delay1.jpg (9.8 KB, 52 views)
	power-delay2.jpg (14.7 KB, 21 views)

Attached Files

power-delay.zip (469 Bytes, 10 views)

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http://relays.tycoelectronics.com/datasheets/CD_DS.pdf
I would use the 12 volt 2 to 180 second delay relay.
rons

 

thank you all of you for your answers except hero999.
on1aag i would like to ask you about the time delay that your circuit has. i would like to be between 40-60 sec approximately.i would like the relay to be on power-on state after these seconds. before these second i would like to be on power-off state.

 

What's wrong with my answer?

It works!

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Hi Tzitzikas,

The relay will be activated 40 to 60 seconds after power is applied
to the circuit. When switched off and back on, again you have to
wait 40 to 60 seconds for the relay to be activated.

on1aag.

 

Apparently he didn't want to think.

 

The same with my circuit.

It can be fixed though.

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Same circuit, but....different value.

I used this if no need precision.
On-delay and fast turn-off.

Attached Images

untitled.JPG (24.8 KB, 20 views)

 

i am looking for digital circuits with variable delay. i am also looking for circuits that they are using pic microcontrollers like pic16f84.

 

hi,
This is not what you said in your OP, why???

Many members have wasted time and effort trying to answer your original query!

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Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Maybe he wants to start a collection ?

on1aag.