Questions- Electric Sprinkler Valve

[Davidvaini]

Note: I will be using this to fire flour and power is not crucial, but remote firing is, so I will be electrically actuating the valve, and not pneumatically. Size and simplicity is crucial so no fancy hookups to squeeze the blowgun or anything like that. Also since it is only flour, if 12VDC will actuate it and get mediocre performance that is okay. Also I know 18v works, I'm not asking if 18v works or not, Im simply asking if 12v 6amp will work.

1. Is 12V 6amp strong enough to fire(actuate) a sprinkler valve for firing flour(not much performance needed)

2. If 12V 6amp is not enough to actuate(fire) the sprinkler valve, is it because of the Voltage or the Amperage?

3. I originally planed on using this:
https://www.allelectronics.com/index.ph ... 10&index=1
To set off the sprinkler valve to fire off some flour (homemade mine), My Question is that, "If the power coming out of this thing is not strong enough, what would I have to add into the mix to get the voltage or amperage high enough? (relay, other)

4. If it is the amperage that is not high enough, there is a 12VDC 15Amp version of the same keychain remote, Will that be enough?, too much? etc?

[Technician1002]

Note: I will be using this to fire flour and power is not crucial, but remote firing is, so I will be electrically actuating the valve, and not pneumatically. Size and simplicity is crucial so no fancy hookups to squeeze the blowgun or anything like that. Also since it is only flour, if 12VDC will actuate it and get mediocre performance that is okay. Also I know 18v works, I'm not asking if 18v works or not, Im simply asking if 12v 6amp will work.

1. Is 12V 6amp strong enough to fire(actuate) a sprinkler valve for firing flour(not much performance needed)

2. If 12V 6amp is not enough to actuate(fire) the sprinkler valve, is it because of the Voltage or the Amperage?

3. I originally planed on using this:
https://www.allelectronics.com/index.ph ... 10&index=1
To set off the sprinkler valve to fire off some flour (homemade mine), My Question is that, "If the power coming out of this thing is not strong enough, what would I have to add into the mix to get the voltage or amperage high enough? (relay, other)

4. If it is the amperage that is not high enough, there is a 12VDC 15Amp version of the same keychain remote, Will that be enough?, too much? etc?

Most people don't pay much attention the the difference AC or DC makes on a sprinkler valve. Lets cover the assumptions.

1 It works the same on AC as it does on DC. Bzzt wrong.
2 A 24 volt valve requires 24 volts. Bzzzt Wrong again

Now that I have your attention, the science behind the answers is needed.

1 Ohms law. I (Current) = Voltage divided by resistance. More voltage, more current on the same resistance. More resistance at the same voltage, less current.

2 Ohms law is only good in DC or AC where there is only resistance and no inductance or capacitance.. OOPS. A coil in a solenoid is an inductance.

3 The magnetic field around a wire is directly related to it's current (Not voltage or resistance)

Now put it together. An AC 24 volt sprinkler valve has the resistance of the wire limiting the current. In addition the inductance also limits the current to a relatively low current. It works fine on 24 Volts AC.

Apply DC and the inductance does nothing.. Now only resistance is the current limiter. IF you leave 24 volts DC on the valve for long you will get smoke. The current is much higher on DC at the same voltage.

The solution is to run at lower voltage to get at least the same current. 9-12 volts DC does this fine. This is why most sprinkler valve work fine on just 1 9 volt battery. You don't need 2 for 18 volts or 3 for 27 volts. It's a waste of money to heat the solenoid.


To now answer the question posed in the original post. Yes it would work fine. Try a 9 volt transistor radio battery. It's lighter.

Yes I am an electronics expert.

[jimmy101]

Besides working out the electronics you can also just test it with a 9V battery. Either it works or it doesn't.

A 9V battery is adequate for a typical 24VAC sprinkler valve. 18V works as well. There are many examples of sprinkler valve guns operated from one or two 9V batteries.

A 9V will only source about 1 amp (and that only when brand new), so at 18V there is, at most, 18 watts dissipated in the valves solenoid. The solenoid can handle that amount of heating, especially since you won't be holding the valve "on" for extended periods of time.

[Technician1002]

Besides working out the electronics you can also just test it with a 9V battery. Either it works or it doesn't.

A 9V battery is adequate for a typical 24VAC sprinkler valve. 18V works as well. There are many examples of sprinkler valve guns operated from one or two 9V batteries.

A 9V will only source about 1 amp (and that only when brand new), so at 18V there is, at most, 18 watts dissipated in the valves solenoid. The solenoid can handle that amount of heating, especially since you won't be holding the valve "on" for extended periods of time.

Give me a few minutes. I'm going to do some measurements. I'll have a solid answer in about 20 minutes. Watch this post for updates.

I'm back. The measurements are in on my sprinkler system. Photos below.
Current is 0.25 Amps.
Volts is 28 unloaded (nothing on) Assuming 24 volts under load.
Using Ohms law, I would expect a coil resistance of about 100 Ohms.

Measured resistance is 21.4 Ohms.. About 1/5th of the expected.

What's that mean for DC?? We need 0.25 Amps to operate the valve. To get 0.25 amps on 21.4 Ohms we need .. Calculator.. Volts divided by resistance. Um need to find volts.. working backwards.. Current times resistance.. 5.35 Volts The valve should work fine on a 6 volt battery. I hope this solves this for you.

Let's test the math.. Current = voltage divided by resistance.
5.35 / 21.4 = 0.25 Amps which is enough magnetic pull to hold the valve.

Before the magnetic core pulls into the core some solenoids have less inductance and draw more current until the core pulls in. The voltage to open the valve may be higher than calculated, but it will hold open on just under 6 volts.

Many gas appliances use this in their design. Many gas furnace valves and propane refrigerators are designed to run on either 24 VAC or 12 VDC to use in mobile homes and recreational vehicles.

[Davidvaini]

Thank you everyone for your answers to my questions, It is much appreciated.

[sprinkler guy]

WAIT! Go back to why the numbers didn't add up according to Ohm's Law! WHY, WHY!??? I'm an irrigation pro with 24 years experience, and I'm stumped on how the voltage, current, and resistance of a sprinkler valve solenoid and controller do not work out right with V=IR. WHAT AM I MISSING??

[Technician1002]

You are missing inductance which counts in AC circuits along with Power Factor. AC is Volts times Amps times Power Factor = Watts. In AC, Volts times Amps is VA.. Volt Amps. VA is used to size overcurrent protection devices and wire size. Power Factor can be any value from 1.0 a resistive load to zero where the current leads or lags the voltage by 90 degrees. You will see this a lot if you work with irrigation pumps. Many that run on 440 Volts AC have DC resistance near one ohm. No it is not shorted.

For a mind blow, if you have a large transformer feeding a residential neighborhood, there may be a high reactive current causing resistive heating loss in the powerlines feeding it. By adding a capacitor in parallel to the line, with the opposite power factor, the reactive current on the line can be reduced near zero lowering the current on the power line. Search for power factor correction to learn more.

Current in an inductor is limited by inductance in addition to resistance. For example a typical fridge compressor has a DC resistance of less then 10 ohms, but has a run current less than 10 Amps.

http://en.wikipedia.org/wiki/Power_factor

Inductive loads have the current lag the voltage. Capacitive loads have current leading the voltage. Only a resistive load has the current in phase with the voltage for a power factor of one.

Knowing this stuff is the difference between an engineer and a technician.

This is why your class two transformers are listed in VA instead of Watts. The coils have a limit on the current they can handle. High power factor can reach the VA limit at relatively low wattages.

The difference between Watts and Volt Amps is known as VARS. or Volts Amps Reactive.

http://en.wikipedia.org/wiki/Volt-ampere_reactive

I disagree with one part of the above wikipedia article..

The correct symbol is var and not Var, VAr, or VAR

I've only seen it as all caps much like SCUBA is Self Contained Underwater Breathing Apparatus. Telling me it is lowercase makes as much sense as scuba.

[sprinkler guy]

I appreciate the fact you know your stuff, but you're going way off the reservation here, which isn't helpful. Please back up and slowly explain inductance to me and how it changes Ohm's Law. I DON"T want to hear about transformers or irrigation pumps or power factors, or have my mind blown. I JUST WANT TO STICK TO THE EXAMPLE OF A SIMPLE SPRINKLER VALVE SOLENOID. Everyone I talk to about this has to go off on a rant to show off how fucking smart they are.

[mark.f]

Tech did explain everything he said, in a 339 word post which probably took a good bit of time to make. Saying that he 'has to go off on a rant to show off how freakin smart he is' was kind of rude.

Would you rather he had just said "The solenoid is an inductive load." and left you to sweat out the rest?

[dewey-1]

I appreciate the fact you know your stuff, but you're going way off the reservation here, which isn't helpful. Please back up and slowly explain inductance to me and how it changes Ohm's Law. I DON"T want to hear about transformers or irrigation pumps or power factors, or have my mind blown. I JUST WANT TO STICK TO THE EXAMPLE OF A SIMPLE SPRINKLER VALVE SOLENOID. Everyone I talk to about this has to go off on a rant to show off how freakin smart they are.

You are missing a simple concept of Ohms Law for AC circuits. Google it!

E=IR for DC circuits. Use E=IZ for AC circuits.
Z=R only in a pure resistive circuit.

In the sprinkler valve example Tech gave;

24 VAC/.25 A= 96 Ohms Z (impedance) Not DC resistance!
DC resistance is 21.4 Ohms
Reactive resistance is 96-21.4=74.6 Ohms at 60 Hz.

[MrCrowley]

I appreciate the fact you know your stuff, but you're going way off the reservation here, which isn't helpful. Please back up and slowly explain inductance to me and how it changes Ohm's Law. I DON"T want to hear about transformers or irrigation pumps or power factors, or have my mind blown. I JUST WANT TO STICK TO THE EXAMPLE OF A SIMPLE SPRINKLER VALVE SOLENOID. Everyone I talk to about this has to go off on a rant to show off how freakin smart they are.

Mate, calm down. You have literally just joined the forum and dug up a 4 year old thread to start shouting about why some numbers don't add up even though you have 24-years of experience and know what you're doing.

Remember, all you asked is:

WHAT AM I MISSING?

And Tech replied:

You are missing inductance

He answered your question and you should apologise for going off on a rant at him when he just spent a fair amount of time answering your question and telling you something interesting that's related to the question.

If you think people here write posts like that just to show how smart they are, you're going to have a pretty bad time on this forum. And if you stick around here long enough, you'll soon be thankful that a handful of members like Tech do take the time to elaborate in their replies rather than just posting a simple one-liner.

[sprinkler guy]

I have a mental illness. I aplogize. Thanks Dewey 1 for your concise answer. I have to learn to control my impulses, anger, drinking, etc. I probably have an inferiority complex among everything else. I notice this forum automatically autocorrects profanity. That's cute. Sorry everyone for being such an A-hole.

[Brian the brain]

I have a mental illness. I aplogize. Thanks Dewey 1 for your concise answer. I have to learn to control my impulses, anger, drinking, etc. I probably have an inferiority complex among everything else. I notice this forum automatically autocorrects profanity. That's cute. Sorry everyone for being such an A-hole.

welcome back Benstern I'd say..
We've had several members that couldn't control themselves or feel the need to stay polite.
They have all been banned.
Let's hope your story will be different.



We can help you with a lot of wiring problems but we can't help you with the way your brain is wired.
I believe most of us are wired slightly differently, not in a bad way though.
And in here everybody is inferior...when compared to JSR...wich makes the rest of us equal.

Seriously:
Don't post in anger, wait it out and rethink your answer.

beyond Spudfiles:
it's not a bad idea to get help if you really have those issues.

I've been to a schrink..got the ADHD thing.And a b****-wife..
Nothing shameful about it..it will help you understand it and deal with whatever you need to deal with.

Impulsive drinkers with anger issues tend to get themselves into trouble.

[sprinkler guy]

Feeling a bit sunnier today. I realized looking back in some of my irrigation literature, the only reason Ohm's Law comes up is as a tool to size wire according to length. They never touched on the fact the law is a DC only concept. Which makes sense, right, since it's an 18th Century concept, and Tesla didn't come on the scene until the 1880's. Knowing this big difference is helping me down another road of ignorance, but a little more helpful. 60Hz means the current is alternating through the circut sixty times a second? is that right?

[dewey-1]

Short answer, YES.
Here is a good link for understanding some of the concepts/theories.
http://www.6pie.com/electronic-theory/o ... rcuits.php

Note: Some countries use 50 Hz main power,