Source for 24vdc Hack

e-bay?

Certainly a good idea and thanks.

It's the scavenger in me looking to cannibalize some old appliance.

Have a great day.

Two car batteries in series?

Sorry, I should have stated that I want to use 120vac as the source.

How about a 24VDC battery charger, then?

The possibilities appear limited only by imagination at present. Crossing them out one by one seems pointless.

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Noisy as hell. We had problems with a 24vdc charger. To power the Arduino we went with an LM 317 off of the 24v and a normal PS.

Old laptop power supply perhaps.

Well we have plenty of them lying around here.

Good source - Thanks!

Now that is an interesting idea...never though of it, but will have to see how that would work.

Thanks!

GA for Fry, I was going to suggest two rectified 12v transformers in series. Give them a common connection and you make a "single" center tapped 24v source. Add a cap across the rectifier to smooth it out.

Just dig through the ubiquitous box of "wall wart" power supplies they probably have in the back somewhere, there is bound to be one that is 24VDC. Remember, you do NOT need to add up the power for all of the solenoids, you are only going to operate them one at a time anyway! You just need a few ma to power your arduino, then whatever one solenoid needs.

But by the way, you are aware aren't you that commecial off-the-shelf sprinler valve solenoids are 24VAC right?

Just from a ramdom pick vendor

irrigation solenoid valve, water solenoid valve, liquid solenoid valve, nylon solenoid valve, plastic solenoid valve

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Specification:

You can power tap before the rectifier for the AC and after the rectifier for the DC in that case.

When it comes to safety, I do not care for any hack. On a workbench yeah, in the garden not on your life. It is getting too expensive there.

Two PC supplies in series.

Quite a lot of the bigger PC units have dual 12V supplies.

For the sake of accuracy, all PC PSUs do have +12V and -12V supplies, but the -12V supply is typically less than 1A. Dual 12V supplies are both +12V.
The problem with using PC power supplies in this context is that they do not like to be so lightly loaded. Conversions for general workbench use usually involve putting a load, something like a 6V bulb, permanently across the 5V supply.

The power supply of a hi-fi amplifier runs at around 30-50V. You could tap some power from that and still make music while you water.

http://www.ebay.com/itm/24V-2A-Charger-for-Razor-E200-E300-Electric-Scooter-/161009816786?pt=Battery_Chargers&hash=item257ceed4d2

10 bucks 50 watts

Look for a "brick" at Habitat or Good Will. They are $1 to $2. You could series 2 if necessary.

Try transformer for outdoor lighting. Everybody has gone to solar, might be some at garage sales or flea markets.

These are all great ideas.

Thank you all for your suggestions - most I have never considered.

I certainly should be able to get something powered up here now.

Have a great day!

Find a junk yard that has some old air conditioning equipment. The transformer in a small split system furnace is 120 X 24 volt ac. In a dual pack, 240 X 24 VAC. Just for sprinkler valves, add a rectifier and cap and let 'r go! -- JHF

Pull the power transformer from a small microwave oven, cut out the high voltage coil, cut apart a second transformer and pull the 120v coil apart and use about 20% of that coils wire to wind a secondary for the first transformer, use a full wave bridge...dc out into a capacitor...measure voltage and add or remove turns to set the voltage where you want it... good for about 10 amps. DVM's wont give an accurate reading without the cap.

Okay...this is only SLIGHTLY embarrassing.

I was talking about this project with a friend who does sprinkler systems and when he said 24v I just jumped to DC in my mind for whatever reason.

Thanks for the clarification. There are many good ac suggestion above and I can do away with the rectifier and cap, but now need to source out a 5vdc to 24vac relay. I am controlling with an arduino.

My wife wonders why I don't just go out and buy something, but that would take all the fun out!

Get a couple more transformers and wire it as a magamp. You put the 24vac through the lowvoltage windings of your two transformers wired in parallel and drive the high-voltage windings with 5-12v from the arduino through a diode. When the arduino is on, the small current from the driver saturates the core and the impedance drops on the lowvoltage side, turning on the 24vac. when the arduino turns off, the impedance rises up and the 24vac drops to just a trickle of current.

I just built one recently to check out this effect and it works very well.

Here is the diagram of the one I built:

https://docs.google.com/file/d/0BzLmZDNLefUnRUd5clg0Qk5zUms/edit?usp=sharing