I am creating a circuit that includes a 24vac sprinkler solenoid. I need it to be portable so I'm planning on using DC current rather than AC. What is the best way to do this? If I just use straight DC current, will this harm the solenoid?
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\$\begingroup\$ See electronics.stackexchange.com/questions/97026/… and ecmweb.com/content/using-ac-coils-dc-power \$\endgroup\$– crj11Commented Nov 6, 2018 at 22:14
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\$\begingroup\$ thanks @crj1. I couldn't find a similar question myself. so i appreciate it! \$\endgroup\$– derekjones562Commented Nov 6, 2018 at 22:25
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\$\begingroup\$ An AC solenoid is NOT the same as its DC equivalent. An AC solenoid or electromagnet or relay has a 'D' shaped loop of heavy copper to cause a phase shift, so the AC current does not cause the device to 'chatter', and its resistance is a reactive property. Feed the same AC device DC and it will overheat fast. \$\endgroup\$– user105652Commented Nov 6, 2018 at 22:25
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4 Answers
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The best way to do this would be to get a solenoid valve rated for 24 VDC.
Your existing valve may or may not be rated for DC operation. We have no way of telling, since you didn't tell us which one it is.
answered Nov 6, 2018 at 22:13
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\$\begingroup\$ This is the only answer to this question. Solenoids are very cheap to replace and widely available and not worth the risk of using it with a voltage it is not rated for. \$\endgroup\$– David777Commented Jun 18, 2021 at 12:03
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If you have to use the 24vac valve then add a series current limiting resistor. Experiment with a larger resistance first and decrease until you get a strong enough "click" to know it is actuating.
The same problem occurs when replacing electric door strikes. The strikes are usually 12 or 24 volts, AC or DC. A DC strike being powered by an AC voltage will give that characteristic bzz-z-z of the front door being unlocked.
Sometimes an AC strike has to go into a DC circuit in an emergency. I add a 10 ohm or smaller resistor, usually 5 watt. Sometimes as low as 3 ohms.
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I had this question myself and the best answer I could find was from https://rayshobby.net/wordpress/understanding-24vac-sprinkler-valves/
In summary, you can run a 24VAC solenoid on 12V DC (note 12V NOT 24V), but be aware it will use more power, run warmer, and reduce the overall lifetime of the solenoid (not sure by how much).
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I totally agree with you Matthys Du Toit - perfect explanation on https://rayshobby.net/wordpress/understanding-24vac-sprinkler-valves/ .... just forget last paragraph in that link... We do not need complex circuit to solve the different current needs of that solenoid (~400mA to start electromagnetic valve and then ~200mA to keep it opened). Just had a 12V 5W lamp in series with solenoide... et voilá. Extra added - it will lit when valve is on.
