how to power on relay when power failure

[cllunlu]

Hello

I have 8 selenoid valfs and control unit with relay. Selenoid valfs run 9V DC and if you want to open selenoid valf, send +9V (correct bias) to valfs just a second. If you wanna close selenoid valfs, send -9V (reverse bias) to valfs a second.

Now, I have designed the circuit, but I am confuse. Because, After selenoid valfs opened, if power failure. Then valf opened more and more times. I want to close selenoid valf when power failure. How can I do it.

how to power on a close relay below images when power failure

 

[davoud]

What is your solenoid valves power?

 

[cllunlu]

What is your solenoid valves power?

9V dc power

 

[davoud]

I mean, need to understand power or current of it.

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I think, if your solenoid valves no need to big power,you could connect a battery bank to your circuit.

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and when you detect power failure,you can trig your valve by -9v

 

[BradtheRad]

You may end up needing two relays, one to apply voltage, and one to choose polarity of applied voltage.

Your schematic has a relay which is like a 2-position switch. You really need something like a 3-position relay, similar to a switch whose center position is not connected. However I've never heard of such a relay.

A large capacitor could provide power briefly when blackout hits. Or else a battery (as suggested in post #4).

 

[Easyrider83]

You need some backup power. Probably capacitor or ultracapacitor.

 

[c_mitra]

Hello

I have 8 selenoid valfs and control unit with relay. Selenoid valfs run 9V DC and if you want to open selenoid valf, send +9V (correct bias) to valfs just a second. If you wanna close selenoid valfs, send -9V (reverse bias) to valfs a second.

Your diagram shows both the relay contacts in the same place. You have now confused me too!