# I need a circuit to open after 5 seconds how?

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#### blackhope121

##### New Member
Hello all,

I designed a circuit that controls a simple 12 v relay. The relay is going to operate a valve that opens and closes. The valve as of now has a momentary rocker switch; holding it one way opens the valve and holding it the other way reverses polarity and closes the valve.

I want to replace switch that comes on the valve and use the relay to operate the valve

What I cannot figure out is how I can make the valve operate for only 5 seconds each way.

Basically when the relay is on i dont want it to be continually trying to open the valve and when the relay is off to be continually trying to close the valve.

I am experimenting with 555 timers but the configurations Ive seen use a momentary switch to trigger the timer. Since the relay is supplying constant power to the 555, the 555 just repeats its timed cycle over and over

any ideas are greatly appreciated

#### MikeMl

##### Well-Known Member
Post a link to the data sheet for the valve.

(I trying to figure out if there only one coil where you reverse current, or two coils?)

#### blackhope121

##### New Member

there is no datasheet unfortunatly.

I am assuming it reverses polarity to close.

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#### MikeMl

##### Well-Known Member
Ok, how many pins in the cable/connector?

Do you own an Ohmmeter?

#### blackhope121

##### New Member
Ok, how many pins in the cable/connector?

Do you own an Ohmmeter?

4 pins.
power ,ground, forward , reverse.

Im at a lab station now. Im assuming you want me test the polarity so ill go ahead and do that now

#### blackhope121

##### New Member
Ok, how many pins in the cable/connector?

Do you own an Ohmmeter?

green get 12v when i close the valve, red gets 12 volts when i open the valve, white is constant 12 power and black is ground.

I was wrong there is not polarity reversal.

#### MikeMl

##### Well-Known Member
This sort of sound like it has a built in "holding" circuit. Is it normally controlled with a center-off spring-return toggle switch, where the Red and Green wires get pulsed only as long as the switch is held off center?

How much current does it draw between White and Black?

If you are watching the valve, what does it do as you connect 12V to the White wire?
What does it do as you remove 12V from the White wire?

#### blackhope121

##### New Member
This sort of sound like it has a built in "holding" circuit. Is it normally controlled with a center-off spring-return toggle switch, where the Red and Green wires get pulsed only as long as the switch is held off center?

How much current does it draw between White and Black?

If you are watching the valve, what does it do as you connect 12V to the White wire?
What does it do as you remove 12V from the White wire?

that is correct about the switch

nothing happens when I connect 12v to the white wire if im not pressing the switch in one direction or the other.

the valve uses about 220mA until it completly shuts then it goes past .5A once its shut. (my machine has a current limiter at .5A

#### MikeMl

##### Well-Known Member
Ok, I'm guessing that the Red and Green power the internal motor through built in limit switches, in which case it shouldn't matter if you leave power applied to Red or Green indefinately. You could prove that by watching the current on your power supply while using the supplied center-off toggle switch. Command it to open and watch the current while holding the switch. I'm guessing that the current drops as soon as the flapper reaches the commanded position, even if you do not release the switch?

#### rainbow86

##### New Member
Ok, I'm guessing that the Red and Green power the internal motor through built in limit switches, in which case it shouldn't matter if you leave power applied to Red or Green indefinately. You could prove that by watching the current on your power supply while using the supplied center-off toggle switch. Command it to open and watch the current while holding the switch. I'm guessing that the current drops as soon as the flapper reaches the commanded position, even if you do not release the switch?

I think so, and you best have a try in advance.

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