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12VDC to 24VAC circuit - is it possible?

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cavik

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Am looking for a circuit that will have an input of 12 volts DC from a sealed lead acid battery and an output of 24 volts AC. I see a lot of circuits that output 110 volts AC but that is to much for what I need. I will be using the circuit to control a single 24VAC Orbit sprinkler valve.
 
If the Orbit sprinkler valve is just a solenoid, you should be able to operated it on DC. Generally, you can run an AC solenoid at a lower DC voltage (Usually 1/2 of the AC RMS) than the RMS AC voltage it is spec'd for. I would test it by seeing at what DC voltage it operates reliably at and then increase that by 50%....
 
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12VDC to 24VAC

Thank you for the quick and informative rely. I will try different DC voltages to see what works. I am not familiar with AC voltages as I have only dealt with DC in the past so I was at a loss as to what to do. This forum is indeed an asset to those of us without expertise. Praise to you all - and continue the good work.

Charlie
 
**broken link removed**

That's a circuit for 12DV to 100AV but he has instructions on how to mod it to turn any DC voltage into any AC voltage.
 
Many sprinkler solenoids rely on increased inductance (reduced current) when the actuator physically moves into the coil. It's not a straight DC relationship.
 
I never would have guessed that a DC source could ever power an AC device but on the advice from kcriste I tried a 12 volt SLA battery on the 24VAC solenoid and it worked flawlessly. I cannot express my thanks near enough for your help kchriste. I would also like to thank napalm for his reply and link to a circuit schematic of the exact circuit I was looking for. Since I am trying to keep the physical size of this unit to a minimum I am going to stick with a simple battery/switch arrangement. But I do thank you napalm for your help also.

Charlie
 
napalm said:
**broken link removed**

That's a circuit for 12DV to 100AV but he has instructions on how to mod it to turn any DC voltage into any AC voltage.
Inverters like that are alright for light bulbs but not much good for other things like audio amplifiers, this one is even worse because it outputs a square wave and not even a modified sinewave!

The preformance evaluation on the website is a bit optimistic too.

The resistance value of the bulb = V2/W = (100)2/60 = 167 ohms
(I assume that this value doesn't change with the voltage.)
It does, at lower voltages the filament will be cooler so it will draw a higher current in proportion to the given voltage.

Also, the voltage and the current are not sine wave.
If the meter on the output isn't a true RMS meter and therefore will only yeild accurate results when measuring a sinewave then it can make a huge difference.

I judged that these errors didn't have a big influence on the result.
Well you've made a serious misjudgement then!
 
it wouldn't take much to make this a sinusoidal generator
replace that square wave oscilator with a sinus gen and drop in a schmitt trigger, you could even use 74HC14 for the schmitt if you scale the signals correctly
 
You mean make it into a class-D amp?

But that would require a filter on the output stage.
 
yer a class-D
as to filter well yer but you may not need it
I mean the machine is rated for 24Vac, it aint gonna be that high of a power, ie not much current.,
Now the thing is he is running of 12V so he either puts a 1:3 transformer in to boost the voltage up (in which case that XFMR will take out the switching freq harmonics) and switch suitable FET's at >50khz and you are gonna get a really good sinus generated and that 50khz component will not appear at the load

or he is gonna have to boost that 12V first to ~40Vdc before invertering in which case a filter will be needed
 
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I would be tempted to put the filter on the primary side of the transformer, I suppose it's possible to put it on the secondary but the losses in the transformer would be higher,
 
true, but depending on how in-depth he wants to go it may just be more convient to drop those harminics into the transformers iron, sure it will be lossy, but its low current
 
The reason that they use AC is prevents the connections and any thing relating to this device from getting verity,grease ( I am not sure If this is spelt correct but it is the same substance you get around your battery terminals in your car ).This will cause bad connections down the track.
Hope this helps.
Greg
 
solenoid activation on DC

wow- DC solenoids take lots of pull-in current but generally much lower holding current to keep them engaged, some pilot operated ones actually use the line pressure to hold them. use a solenoid driver circuit to save battery power wasted on holding the thing in. see 555 solenoid drivers- google it for samples.
 
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hi all,
am looking for a transformer less power supply ckt. in which i have to convert a 230v ac to 5vac or 12v . i required a max of 30mah .plz post a diagram i will be very thankful to you.

thomasplam.
 
You can use a Power pack that has a 12V AC output The power packs are used on Modem's Charging Battery drills. ETC not the DC ones.
Do you require The Voltage to be changed from 12 V ac to 5V ac
The current is not important as long as the current is above the required level you want. The device will only pull the amount of current as required.
I hope this Helps .
What is the device you are going to use this voltage on.
 
Old thread but I assume he solve the problem.

I would've just tested it on 12VDC, then if it didn't work, boosted the voltage to a higher DC level which would work. As said above it's a solenoid so should work on DC as well as AC, but the DC voltage should be lower.
 
Ok so a similar question. I want to run a 24vac unltrasonic mister like this one **broken link removed**

off of 12 or 24VDC. will that work like the solenoid or is this a horse of a different color?
 
It'll probably run from DC but you might need a higher voltage than 24V. It's electronic and will just have a rectifier and filter capacitor after the power input. The peak voltage of a 24VAC is 34V but there'll be rectifier losses and ripple so it will work at a lower voltage. You could try it at 24V and it might work but you might need to increase the voltage to 28V or even 30V before it will work.

You could always ask the seller but they might just say no because they don't know any better.
 
Am looking for a circuit that will have an input of 12 volts DC from a sealed lead acid battery and an output of 24 volts AC. I see a lot of circuits that output 110 volts AC but that is to much for what I need. I will be using the circuit to control a single 24VAC Orbit sprinkler valve.

If you do ever want to upgrade to more valves including the full feature set of a timer, PowerStream Technology makes an Inverter that goes from 12VDC to 24VAC pure sine wave.
 
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