24VAC from 24VDC power supply

Thread Starter

DJ_AA

Joined Aug 6, 2021
152
Hi

Is it possible to create 24V AC from a 24VDC power supply, using passive components or semiconductors?

I am aware you can create DC from AC using diodes but what about the opposite way.

I need 24VAC to control some solenoids.

Traditionally I have used bulky 240VAC to 24VAC transformers, I would like to know if there are other options?
 

paulktreg

Joined Jun 2, 2008
813
I think AC soleniods can sometimes be used on DC but you'll need to fit a series resistor to limit the current to what is drawn on AC.
 

Papabravo

Joined Feb 24, 2006
18,417
Hi

Is it possible to create 24V AC from a 24VDC power supply, using passive components or semiconductors?

I am aware you can create DC from AC using diodes but what about the opposite way.

I need 24VAC to control some solenoids.

Traditionally I have used bulky 240VAC to 24VAC transformers, I would like to know if there are other options?
The circuit is known as an inverter and it converts a DC voltage to an AC voltage. This can be either a modified sine wave or a true sine wave. The former is a simpler circuit and the latter is more complicated.
 

Thread Starter

DJ_AA

Joined Aug 6, 2021
152
I am not sure if there are multiple different types of solenoids, but these are used on valve from companies such as rain bird or hunter.
 

LowQCab

Joined Nov 6, 2012
2,047
The best and most reliable solution is a Transformer.
That's why companies like Rain-Bird and Hunter always use Transformers.
Electronics tend to suffer out-doors from the Humidity, Temperature-Swings, Bugs,
You name it, it will get in there and cause a problem eventually.

If You want a Battery-Back-Up-System,
install a UPS INSIDE the House, or
at the very least, in a very large, Aluminum, Water-Proof, Out-Door-Rated, Cabinet.
.
.
.
 

Thread Starter

DJ_AA

Joined Aug 6, 2021
152
Battery back up is not necessary.

I was just wanted to see if there is an alternative to a transformer. As its starts getting very bulky in the enclosure.
 

crutschow

Joined Mar 14, 2008
29,791
would all solenoids work on DC or just some?
I would think just about all AC solenoids will work on DC if the DC current is limited to the RMS current it draws on AC.

If not, for solenoids you could likely just use a square-wave AC signal, so a MOSFET H-bridge driven at 50-60Hz and powered from a 24V supply to give a ±24Vrms square-wave should work.
I was just wanted to see if there is an alternative to a transformer. As its starts getting very bulky in the enclosure.
My sprinkler controller uses an AC output wall-wort so doesn't take any room in the enclosure.
 

MisterBill2

Joined Jan 23, 2018
11,880
I am not sure if there are multiple different types of solenoids, but these are used on valve from companies such as rain bird or hunter.
Several years ago, when there was a several day power outage in the winter and a relative had no power for the gas valve on their heating boiler, I was asked to help.
Very fortunately the boiler has a 24 volt AC control system, and all of the connections were accessible. Also, fortunately, he had a charged 12 volt battery from his RV.
For three days that battery powered the gas valve on the boiler so that the house did not get cold.
This is an example of DC operation of an AC solenoid. Certainly 24 volts DC will operate a 24 volt AC solenoid, but there will be a problem of overheating because only the resistance of the solenoid coil will limit the current, while with AC operation thecurrent in a solenoid coil is limited by both the resistance and the inductive reactance of the coil. So you could use a resistor to limit the current, or, if the supply is series batteries, tap in at a lower voltage. That will require a bit of experimenting, to keep the DC wattage at or below the AC wattage.
 

MisterBill2

Joined Jan 23, 2018
11,880
Our experience was operating an AC valve on half the voltage DC. That worked in that instance. The thing to do will be to have the same power delivered with the DC source. For a sprinkler control system one simple way to avoid a bulky wall-wart transformer is to use an electrical box mounted transformer and then just run a pair to the sprinkler control assembly. Much more reliable and nicer looking as well.
 
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