One question I get asked a lot is "how do you power a controller on your workbench?"
It's so simple I almost hesitate writing about it, except that folks might not try it for fear of damaging their crazy expensive system...
We're all used to seeing the 12(or 10)/18/24 volt AC system transformers in our outdoor panels, but when I first started tinkering with Pentair stuff, an Intellitouch "laptop trainer system" found it's way into my possession...
And it was powered by a single 12 volt DC wall wart. Huh?? The system transformer puts out AC volts, not DC volts!
I noticed that the 12 and 18 volt AC inputs are converted on-board to DC (while the 24 volt AC input is left alone). The 18vac converts to about 24vdc and powers all of the relays, while the 24vac powers the valves... none of which is present in the trainer system.
Further inspection revealed an on-board regulator that drops the 12vdc down to 5vdc to run all the logic circuitry. It was now apparent that as long as you got the polarity right you could feed 12 volts DC straight into the 12vac input - since it's going to be converted to DC anyway.
So that's how Pentair powers their trainer systems, and that's what I do on my bench:
The only caveat is that since I'm typically troubleshooting a damaged system, I use a "lab power supply" instead of a wall wart or generic power supply (my HP/Agilent E3610 lab supply is pictured above).
A lab power supply lets me set a current limit whereas a wall wart (or any supply without a current limit) will gladly pump out it's maximum rated current if asked to do so - which could potentially damage the device under test and/or the power supply!
I've got an upcoming post on repairing an Intellitouch indoor controller where the current limit came in real handy...
It's so simple I almost hesitate writing about it, except that folks might not try it for fear of damaging their crazy expensive system...
We're all used to seeing the 12(or 10)/18/24 volt AC system transformers in our outdoor panels, but when I first started tinkering with Pentair stuff, an Intellitouch "laptop trainer system" found it's way into my possession...
 |
| It's a full-fledged Intellitouch, but has different firmware and no means to power the relays and valves. |
And it was powered by a single 12 volt DC wall wart. Huh?? The system transformer puts out AC volts, not DC volts!
 |
| This 12 volt DC wall wart was glued onto the trainer system |
I noticed that the 12 and 18 volt AC inputs are converted on-board to DC (while the 24 volt AC input is left alone). The 18vac converts to about 24vdc and powers all of the relays, while the 24vac powers the valves... none of which is present in the trainer system.
 |
| I've circled the rectifiers that convert the 10 and 18 volts AC to DC |
Further inspection revealed an on-board regulator that drops the 12vdc down to 5vdc to run all the logic circuitry. It was now apparent that as long as you got the polarity right you could feed 12 volts DC straight into the 12vac input - since it's going to be converted to DC anyway.
So that's how Pentair powers their trainer systems, and that's what I do on my bench:
 |
| The left-most pins are where I feed the 12 volts DC, note the polarity! |
The only caveat is that since I'm typically troubleshooting a damaged system, I use a "lab power supply" instead of a wall wart or generic power supply (my HP/Agilent E3610 lab supply is pictured above).
A lab power supply lets me set a current limit whereas a wall wart (or any supply without a current limit) will gladly pump out it's maximum rated current if asked to do so - which could potentially damage the device under test and/or the power supply!
 |
| Another much less expensive programmable supply that I use... currently set to 11vdc and 300mA max. |
I've got an upcoming post on repairing an Intellitouch indoor controller where the current limit came in real handy...
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