Cannot turn Solenoid off

[timmy]

Hi, my setup:

#OpenSprinkler Raspi 1.1 04/2013
#Raspberry Pi Model A
#interval_program 21/July/2013
#Bermad Irrigation Solenoid 24V/AC-2Way S-390-2-R 24VAC 125mA 1.7 Watt http://www.ebay.co.uk/itm/Irrigation-Solenoid-Valve-3-4-Female-BSP-/380321180556?ssPageName=ADME:L:OC:GB:3160
#PSU: Output 24V 1.1A (From an old EPSON Printer)

Pi and the interval_program are up and running fine, able to load the web page and open the Solenoid, but, I am unable to turn it off unless I unplug if from the COM port.

Any suggestions what I maybe able to do to troubleshoot such a problem? Any comments on the items I am using, I believe all are compatible?

Many thanks,
tim

[Ray]

Check if your transformer is 24V *AC*, not DC. If it’s a DC transformer, you will only be able to turn on valves and not turn off. This is due to the way triacs work.

[timmy]

Hey Ray,

I changed my DC Solenoid for a AC model after we spoke on the forum.

Here is what’s printed on the Solenoid it self:

( fyi i take it transformer = Solenoid)

[Samer]

I think the issue is this:

#PSU: Output 24V 1.1A (From an old EPSON Printer)

Which is most likely a DC PSU. I believe that needs to be an AC PSU.

[timmy]

Hey Salbahra,

PSU is label as a AC Adapter, here is a screen grab:

[Ray]

I think the label ‘AC adapter’ here is a bit misleading. This seems clearly a DC adapter (or more strictly AC to DC adapter). Note the label that marks the – / + of the connector.

Another way to tell is to use your multimeter to measure the AC voltage of the output of the transformer. If the transformer outputs DC, the AC voltage reading will be almost zero.

You will need an AC adapter, such as this one:
http://www.homedepot.com/p/Orbit-Transformer-24V-750Ma-57040/202899607#.UfWLPReJBpl
You can also search ‘sprinkler transformer’ on Amazon and there are plenty of choices.

[timmy]

Thanks both, I did have my suspicion regarding the PSU.

Was hoping to use something from the large box of PSUs I have, ill find a replacement and update the thread with my results.

thanks again, tim

[timmy]

Hey both, wanted to keep this post up to date for other UK purchasers.

So it seems almost impossible to find a AC to AC transformer in the UK, after getting a second transformer online that was AC to DC I ended up walking into a Maplin store to pay an outrages £20 for a AC to AC adaptor:
AC 24v
1500mA

Please to say this works great, but im not that happy with the quality of the transformer – its very large and makes a loud buzzing noise.

Im going to be in US for work next month, so going to order a Rain Bird UT1 Sprinkler System Timer Electric Transformer from amazon: http://www.amazon.com/Rain-Bird-UT1-Sprinkler-Transformer/dp/B000DCN8LS/ref=sr_1_1?ie=UTF8&qid=1375565707&sr=8-1&keywords=sprinkler+transformer

Maybe a DC model of the OpenSprinkler system could be produced for us UK people 😉

[Ray]

First, you should be careful buying an AC/AC adapter from the US and use it in the UK. The mains here are 110V, and I believe in the UK it’s 230V. If you use the rain bird transformer (110V -> 24V AC) in the UK, it will probably output 48V AC, which will destroy OpenSprinkler in no time.

It’s possible to modify OpenSprinkler to use DC power instead. The power conversion circuit works with DC as is, so no need to change that. However, the triacs need to be replaced by transistors or mosfets in order to interface with DC devices. Flyback diodes should also be added to interface with sprinkler solenoids. On the microcontroller-based OpenSprinkler 2.0, the PCB design has considered these potential modifications (including PCB holes for both transistors/mosfets and flyback diodes). But OpenSprinkler Pi doesn’t have these yet.

The main reason *not* to go with DC is that most sprinkler solenoids are designed to work with AC power. So all standard sprinkler controllers are also powered by AC adapter. Since we don’t make custom sprinkler solenoids, we have to stick to the industry standard. While you can probably operate them with DC as well, there is a liability issue if things go wrong.

So in the end, we can leave these options available, but you have to make your own modifications if you want it to work with DC, well, unless if you can convince me that in the UK market, most sprinkler solenoids operate on DC power 🙂

[timmy]

The Solenoids I have seen and originally purchased where DC in the UK – but that’s just my experience no way I could comment on the full UK market 😉

Thanks for the advance on the transformer, I think I just found what I need on ebay – will report back!

[timmy]

Got my new transformer (24V AC 500mA) off ebay – after 3 days use its dead!

So back to the buzzing AC 24v 1500mA what’s frustrating.

Not having much luck! Going to find another AC to AC transformer supplier.

Quick question:
– do you recommend > 500mA for the sprinkler pi?
– does it matter what order I wire the transformer in?

thanks,
tim

[Ray]

It’s recommended that the 24V AC transformer is rated 500mA or above. If you searched for ‘sprinkler transformer’ or ’24v ac transformer’ on Amazon, there should be some available choices. For example, this one on amazon.co.uk:
http://www.amazon.co.uk/Orbit-57056-European-Transformer/dp/B004RUHA5M/

As long as it’s AC transformer, it doesn’t matter which order you insert the wires — AC has no polarity.

[timmy]

thanks Ray, guess its just bad luck with the transformer I had.

Will search for another one, the one you have shown is the only one on amazon.co.uk, this has a US style plug so prefer to avoid it

[Author]

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