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ddllmcb

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Posts: 3
Reply with quote  #1 
Greetings, I need to set up remote irrigation timers for my vineyard and orchard.  Irrigation timers come with a 24V step down transformer for plugging into a 120Vac outlet.  I can buy equipment to rectify 12Vdc from panel-charged batteries into 120Vac, but this seems to be overkill for this simple application.  However, I can not find any equipment for rectifying 12Vdc directly to 24Vac.  A timer requires perhaps 0.1 amp or so, and draws power for an hour or two a day at the most, usually a couple hours a week.

I want to build 8 or 10 of these.

Thoughts?

Thx

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ddllmcb

stmbtwle

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Posts: 2,768
Reply with quote  #2 
Could you use a 12vdc timer?
https://www.amazon.com/uxcell-Digital-Power-Programmable-Switch/dp/B008999RYY/ref=sr_1_5?ie=UTF8&qid=1491659647&sr=8-5&keywords=12v+timer+switch

Also available in 24vdc
https://www.amazon.com/Baomain-CN101A-Digital-Programmable-Switch/dp/B01ASMV15W/ref=sr_1_1?ie=UTF8&qid=1491659860&sr=8-1&keywords=24v+timer+switch

More of them on ebay, and videos on Youtube

You probably need to power the valves, too. Some will work on 12vdc.
http://rayshobby.net/understanding-24vac-sprinkler-valves/

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Rick H Parker

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Reply with quote  #3 

"However, I can not find any equipment for rectifying 12Vdc directly to 24Vac."

First off many AC devices have rectifiers in them, they will run off AC or DC. Some contractors run their 120V AC power tools off 70 - 120v DC battery bank.

Hook the timer straight up to 24V DC, good chance it will work. At the worst you might burn up the test wire or pop a fuse.

 

If it powers up on 24 DC then, what your looking for is called a Buck Converter, Also Known As a DC-DC converter. Google "12 to 24 buck converter" to get started.

Here is an example: http://www.ebay.com/itm/Silver-Gray-Dampproof-DC12V-Step-Up-to-24V-240W-10A-buck-Power-Converter-generic-/111584260878?hash=item19faf0b30e:g:fzgAAOSw0e9Ux1Ha

Because your power requirement are only ~1.2 watts, you can find some for a lot less then $22.00 each. It just harder to find them because most small 12/24 buck converter are step up not step down and you most likely want weather proofing not just the board.

This $1.63 board would work if you can find some place to stick it out of the weather. Adjustable 2-24V input to 5v-28v out at 2.0 amps current capability.

http://www.ebay.com/itm/2A-DC-Boost-Step-up-Adjustable-Converter-Micro-USB-2-24V-to-5v-28v-6v-9v-12v-24v-/262520903830

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Rick H Parker


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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
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