Howto power 24VAC valves from 12VDC

Go To Last Post
60 posts / 0 new

Pages

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hi,

 

Just found this forum and it gave great info.  I'm pretty much trying to do the same as post #1 and found post by EcoEvan most interesting so I tried that solution.    I am using an Orbit sprinkler timer as my 'float switch'  .  I actually connect it on the other side of the resister in that diagram.      The listed solution almost works for me.   The Rainbird solenoid on the valve opens without problem as directed by the timer.  The problem is it won't close even after the timer expires.    I know the timer itself works because if I try it without a load or using with 24vac power as designed the valve opens and closes as desired.   I am hoping someone can provide some insights on how to get it to close.    I called Orbit and they would not provide schematics for their timer.

 

I have tried various resistor values ranging from 45 ohms (which yields 132mA) to 220 ohms (45mA) and they all seem to open the valve but none will close it.

Suggestions much appreciated.

 

 

Attachment(s): 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

kingsmith wrote:
solenoid on the valve opens without problem as directed by the timer.  The problem is it won't close even after the timer expires

Maybe you've permanently magnetised something?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

awneil wrote:

kingsmith wrote:
solenoid on the valve opens without problem as directed by the timer.  The problem is it won't close even after the timer expires

Maybe you've permanently magnetised something?

 

Sorry I meant it won't close unless I manually remove the 12V source to the timer.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Perhaps you'd best show us a schematic of your setup...

These give me pause:

  • "...I manually remove the 12V source to the timer."
  • "...using with 24vac power as designed..."

 

 

David (aka frog_jr)

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

If you’re running the controller from 12VDC and it expects 24VAC, then i can understand why it is not working as you’d like.
The controllers normally use a triac to switch the solenoid and rely on AC to function correctly. One way around this is to modify the controller to use mosfets or relays. This means reverse engineering the controller. Alternately, i dare say someone has made a watering controller with an arduino with battery and solar charger.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I can't modify the controller without a schematic.   I updated my diagram in post #52. Anybody else with ideas?   Not understanding how technically the solenoid is affecting the timer from dropping the 12V. As mentioned earlier , timer drops the 12V if no load/solenoid is attached.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Draw a schematic then! The average watering controller is not that complex. Post some photos so we can see components and tracks.
How are you measuring the output? If the load is below a certain value, the triacs won’t latch, so that may be confusing you.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

kingsmith wrote:

Not understanding how technically the solenoid is affecting the timer from dropping the 12V.

If the output switch is a triac (as mentioned), it cannot turn off the load in DC. It relies on the fact that the AC current passes through zero each time before switching polarity. In DC, a triac can only turn on the load. Read here https://en.wikipedia.org/wiki/TRIAC

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Thanks, appreciate the insight.

Pages