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How do I run a 24VAC solenoid off of a couple of 9V's?

cherrington

Feb 11, 2013
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So I have a 24VAC Rain Bird sprinkler valve that I am using for a compressed air rocket launcher. I need to somehow convert this solenoid to a DC current so I can use it with a couple 9V batteries. The solenoid is a 24VAC-50-60Hz. Any Ideas?

Here is the sprinkler valve:http://store.rainbird.com/product/detail/B72421-M.aspx

Type of compressed air rocket launcher I am building:

(Where I live I cannot get the sprinkler valve that you would normally use for this)
 
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duke37

Jan 9, 2011
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I could not find any current specifications on the website.

A simple solenoid will work on DC better than AC so you will need a lower voltage/current.

The AC current is determined by the resistance and inductance. The DC current is deternined by the resistance only. Measure the resistance with a meter and then calculate the current with 9V. I = V/R Make sure the battery can supply this current. I expect that a PP3 will not.
 

cherrington

Feb 11, 2013
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I think that there are a couple tabs below that have the specifications on the sprinkler valve. I don't know much about electronics so could you please explain this to me a little simpler or easier? How do you measure the resistance?

Thank you!
 

Harald Kapp

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Simply try it with DC. Without knowing the internal circuit of the valve, it is hard to say, which modifications are required.
Normally a solenoid is by nature DC operated and special means are adopted to make it usable with DC.
 

cherrington

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I have tried it with three 9V and the solenoid makes a noise but there is no movement. So DC doesn't work I think. When it runs off of AC it needs 50-60 Hz so this might be the problem.
 

Harald Kapp

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Please do not post the same itm multiple times. I merged the 2 threads.
 

duke37

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To measure resistance you need a meter which will measure resistance. There are many cheap digital meters which will measure volts, AC and DC, current and resistance.

Did you have the batteries in series or parallel? If the batteries are in series you should measure 27V. Check that this does not drop much when the solenoid is connected.
 

duke37

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Inrush current 0.41A.
Assume in a worst case that this will apply to DC also, you will need a fair sized battery for this.

Holding current 0.28A.
The holding current will be less when the solenoid is pulled in because the inductance is increased. The DC current will not decrease when the solenoid is pulled in.

As a comparison, a Norslo 240V AC relay will pull in just with 130V AC
It will pull in with 60V DC.

The ratio between these voltages will depend on the magnetic circuit but may give some idea. I would think you need between 6 and 12V and 1/2A.
 

CDRIVE

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I believe your solenoid will operate fine from 12VDC to 16VDC but you can forget about using a 9V battery and this is not because of the voltage. 9VDC would probably produce just barely enough current to pull in the solenoid. The problem is that a little 9V battery is not going to maintain 9V. The instant that the solenoid switch is closed that little battery will probably drop to 7V and continue dropping if the circuit remains closed..

Chris
 

(*steve*)

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36 ohms will mean a current of 250 mA at 9V, it would be 500mA at 18V (which is what you get with two 9V batteries in series).

250mA is pretty much beyond a type 916 9V battery (which is what most people mean when they say "9 volt battery"). 500mA is an even longer stretch.

These would simply be unable to maintain anywhere near 9V for any length of time with this load.

If you placed 6 or maybe 8 of these 9V batteries in series/parallel I think it would work -- but even then, not for long.

(and yes, the voltage would drop off)
 

cherrington

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So do you have any suggestions on what I should do? Just try to hook up six or eight 9V's?

Thanks!
 

duke37

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Try it on a 12V battery such as in a car.

36 ohms will take 333mA.
Dissipation will be 4W which should not overheat the solenoid since there is no AC component.

If it works, get a 12V lead/acid rechargable battery.
 

duke37

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There is NO AC component when running on DC.

When running on AC, the current alternates in direction and induces currents in any conducting material nearby by transformer action. Pole pieces are normally laminated to reduce this effect.
 

CDRIVE

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You didn't specify whether the Solenoid Valve is part of the rocket or part or the ground based launcher. To function as a rocket I would think that the compressed air is released from an on-board tank. If so, the solenoid valve would also be integral to the rocket.

Obviously a large heavy battery would be out of the question in the above scenario. This would dictate that the battery be ground based. In order for the battery to stay on the ground the solenoid valve would have to be mechanically modified to latch open after being energized because the battery isn't taking the ride. Capice?

Chris
 

cherrington

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The Solenoid valve is not part of the rocket itself. It is just a quick release valve to let the compressed air out of my compression chamber and then shoot the rocket up.
 

CDRIVE

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The Solenoid valve is not part of the rocket itself. It is just a quick release valve to let the compressed air out of my compression chamber and then shoot the rocket up.

The compressed air chamber remains on the ground?

Chris
 
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