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latching solenoid valve

kadil

Apr 7, 2014
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Hi,

I am trying to make a battery powered garden timer with a stack of solenoid valves I have come across. The solenoid on the valve model is a bermad S392 and the data sheet indicates that 9v connection one way will latch the valve open and 9v the other way will latch it closed.

My experimenting yields different results. The valve is normally closed and supplying 9v opens the valve while energised but when the 9V is disconnected, it fails to latch. I have tried adding a 4700uF capacitor and also tried a 12V lipo battery (capable of 30A) and I get the same result.

Any assistance would be appreciated.

Thanks,
Kim
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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25,506
Can you post a link to the datasheet?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Have you tried operating the solenoid detached from the valve to make sure it is operating?
 

kadil

Apr 7, 2014
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Yes, when detached from the valve, I can see movement when I apply power, but no latching. Same as with valve attached. When energised the valve allows water through. I have 10 of these solenoid valves and they are all behaving the same way.

I was thinking there might be some bounce behaviour making it delatch when de-energised, but I am clutching at straws.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Do you see the solenoid move one way with one polarity and the other way with the opposite polarity?
 

kadil

Apr 7, 2014
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Yes, one way it spits the core out, the other way it withdraws the core but when deenergised it spits the core out due to the spring behind the core
 

shumifan50

Jan 16, 2014
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As a matter of interest; Have you tested it with water flowing through it as some of these valves use the water pressure to latch the valve open to save battery life.
 

kadil

Apr 7, 2014
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As a matter of interest; Have you tested it with water flowing through it as some of these valves use the water pressure to latch the valve open to save battery life.

Yeah tried that but water only flows while the solenoid is energised.

Tomorrow I will try this:
snapshot1.png

Datasheet says it needs 4700uF cap to drive it and it is a 2W solenoid. These figures should provide the required pulse without providing an ongoing surge of power, unless I get other ideas. Thoughts?
 

gorgon

Jun 6, 2011
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Have you tried to pulse it like it says on the datasheet? I suppose you need to use the 4700 uF to source the pulse current. The coils is 6ohm so you need a fairly large current pulse to magnetice the actuator.
 

kadil

Apr 7, 2014
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I have tried it with the capacitor and a little 9v battery. No good.

Then I tried it with a 12v lipo battery capable of 40 amps. Still no latching.

Sometimes you know it's something simple that is wrong but just cannot put your finger on it.
 

gorgon

Jun 6, 2011
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How do you time the pulse? From your drawing I supose you do it by hand, and that may not be good enough.

The datasheet define the pulse time to be between 20-100ms, which is hard to do by hand.
 

kadil

Apr 7, 2014
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gorgon

Jun 6, 2011
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The ULN2003 can only drive max 500mA on each output, and the solenoid will take 2A from 12V (6ohm resistance), You should get a more powerfull output device, like a NMOSFET with a logic gate voltage range.
You should also do something to protect the MOSFET from the reverse voltage spike from the solenoid, but I would think that a normal diode would interact with the latching function. I would have used a resistor/ capacitor in series over the coil to snubb the peak.
 

shumifan50

Jan 16, 2014
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Running an Arduino will negate much of the low power benefits if this valve.
Why not look at
NE555 One shot timer

You can use the same output arrangement to get the current needed.
 
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