Irrigation Controller conversion Issues

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wisted

1 post

Wannabe Geek

#201756 2-Sep-2016 09:28

Looking for some help with the following problem: I'm trying to control 26 water valve stations with a newly purchased Hunter Irrigation Controller. It is replacing an old controller. The old controller was energizing 26 valves with 24vdc .24 amp solenoids at 26 different times,1 at a time. The new controller will do the same except its output is 24vac. I would like to keep the 24vdc solenoids and build circuit boards to convert 24vac to 24vdc. I know if I make a simple bridge rectifier(NTE166) it will work "if" I keep the - leads separate from each solenoid. I really don't want to do that. The problem I am having is if I use - as a common for the other solenoids I will get 12vdc on the the non-energized solenoids(energizing them) when I only programmed 1 to turn on. I believe I am getting AC ripple. I read you can control this ripple by inserting a capacitor and a resistor in the circuit(see schematic). I don't know what rating cap and resistor to use. Any help would be appreciated.

k14

629 posts

Ultimate Geek

#1621292 2-Sep-2016 11:09

Why don't you just buy 24AC solenoids? They are the standard irrigation solenoids, might cost you a bit up front but is by far the simplest way to go about things. Look on ebay if you wan to save some $$, irrigation equipment is very expensive over here.

MikeAqua

7779 posts

Uber Geek

#1621315 2-Sep-2016 11:38

Thinkīng out loud here but what if you use a diode on the negative lead for each solenoid? This will force unidirectional current flow.

Mike

Masterpiece

247 posts

Master Geek

#1621639 2-Sep-2016 20:38

Don't make it difficult.
You can get power supplies for roughly $100nz, 50~240vac input 24dc out, quite often the ins and outs are selectable. Google for local supply of a unit.

Why didn't you get a controller that matched your solenoids?

Me:"I'm not a robot!"

ET: "Maybe; you have some freewill, but you chose your path by arrangement"

Me "That sounds like a program with no freewill?"

ET: "We will catch up when you end this cycle"

Me: "Sounds like a 'KPI'!"

ET: "Did you read the terms and conditions?"

Me: .....

solutionz

589 posts

Ultimate Geek
Inactive user

#1621866 3-Sep-2016 11:38

Masterpiece: Don't make it difficult.
You can get power supplies for roughly $100nz, 50~240vac input 24dc out, quite often the ins and outs are selectable. Google for local supply of a unit.

Why didn't you get a controller that matched your solenoids?

+1, I would try connecting a 24VDC power supply to your controller as it will be stepped down and rectified anyway power the controller's IC and 24VDC should be passed through to the solenoids.

If you really want to rectify the AC input yourself you need to connect the AC outputs of your power supply to the AC inputs of the rectifier, and the DC outputs of the rectifier to the AC inputs of the controller.

Image result for bridge rectifier

If you find other solenoids a powering when they're not meant to be you have probably mistakenly connected your solenoid common to your AC neutral insted of your rectified DC negative.

If you find DC is not being passed through the controller due to an internal isolation transformer your only option is to use a rectifier for each solenoid. Or as @MikeAqua alluded to you could try simply adding a diode to the controller-side of the solenoid's common and seeing how they will work on a half-wave.

Handle9

11389 posts

Uber Geek

Trusted

Lifetime subscriber

#1621870 3-Sep-2016 11:50

I'd run the 24VAC into interposing relays with a 24VDC power supply for the contact side. Simple and cheap to do.

You won't get a nice DC signal from a bridge rectifier.

Aredwood

3885 posts

Uber Geek

#1622743 4-Sep-2016 21:29

k14:

Why don't you just buy 24AC solenoids? They are the standard irrigation solenoids, might cost you a bit up front but is by far the simplest way to go about things. Look on ebay if you wan to save some $$, irrigation equipment is very expensive over here.

Fully agree. Also AC is better because if moisture gets through the insulation of your solenoid wiring. With DC you will get electrolytic corrosion, While with AC you don't tend to get it.

Also have you tried AC onto your existing solenoids to see if they will still work?

I have an old Toro DDC 8 irrigation controller. Which runs on and outputs 24VAC. I opened it up to see how it switches it's outputs. It uses 1A TRIACs. So my controller probably won't like having rectifier circuits connected to it's outputs. And it definitely won't work if I connect DC to it's power input terminals.