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250 posts

Master Geek
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Topic # 241065 9-Oct-2018 11:29
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Ok you electronic guys - what is the simplest way to do this?
Home swimming pool solar control.
Tried using a SS 12VDC solenoid but after a few seasons it was seizing up so have ordered from AliExpress a “TF40-S2-C DC12V 2 Wires SS304 11/2'' dn40 Full Port 10NM Actuated Ball Valve On/Off 15 Sec For Water Treatment Swimming Pool”
Solar unit turns on (230VAC) when roof water warm enough. Powers on (12VDC via transformer) the motorised valve and it closes and remains closed and then powers down.
Solar unit turns off when roof water cooler. Ok how to get a burst of power to open the motorised valve?!
Thanks




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Uber Geek
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  Reply # 2103863 9-Oct-2018 11:46
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Are you talking about a solar water heater on your roof? The big things with the black tubes?
Can you do a diagram to show how everything is plumbed so it makes sense.

I also wouldn't go expecting much from a solenoid from Ali Express lol, the farms we had while growing up had a whole range of automated irrigation and we found cheap valves don't last, pay for what you get...






 




250 posts

Master Geek
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  Reply # 2103888 9-Oct-2018 12:47
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Thanks but the plumbing layout and quality of the valve have nothing to do with what am asking about.
Attached is a wiring diagram of the valve.





Why work on Wednesday and stuff up 2 good long weekends

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  Reply # 2103899 9-Oct-2018 13:15
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If your control system is giving constant power for the duration that you want the valve to be open, then a solenoid/diaphragm valve is probably more appropriate (not sure if they are available in DN40 though). Your valve not only needs a short burst of power at the start, but also a short burst of power with reversed polarity at the end.

 

All doable if you are into electronics (I'd probably use an arduino with a couple of relays) but TBH it's probably cheapest/easiest to just get a more suitable valve that you can hook up directly to your 12v transformer. There's plenty of off the shelf time delay modules for the other way around (short burst of power triggers something to stay on).

 

Often the solution isn't exactly what you envisaged, hence why people that want to help might ask about the broader context of your problem


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  Reply # 2104095 9-Oct-2018 19:26
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You can wire up a double pole double throw relay to do what you want. Assuming that the valve manufacturer is telling the truth, that it won't burn out if you leave the power permanently connected to it.







250 posts

Master Geek
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  Reply # 2104224 10-Oct-2018 08:07
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Thanks for that.
Any links of where can find one of those in NZ?




Why work on Wednesday and stuff up 2 good long weekends



250 posts

Master Geek
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  Reply # 2105371 10-Oct-2018 10:52
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stuffed: Thanks for that.
Any links of where can find one of those in NZ?

Found this on TradeMe - will it do the job?
https://www.trademe.co.nz/electronics-photography/other-electronics/electronic-components/switches/listing-1793925351.htm?rsqid=2f24b5c1c0f44e61b4e5158be989e774
Thanks




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  Reply # 2105433 10-Oct-2018 11:39
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Aredwood: You can wire up a double pole double throw relay to do what you want. Assuming that the valve manufacturer is telling the truth, that it won't burn out if you leave the power permanently connected to it.

 

Wouldn't you need 2x 12v power supplies for this - one which is controlled (controls the relay) and one which is always on (goes through the relay to activate the motor to drive the valve)? Otherwise, at the end of the day when the temp goes down (which presumably triggers the 240VAC supply to turn off), the loss of controlled 12VDC would turn the relay off, flipping the polarity supplied to the motor, but there would be no power applied for the motor to close the valve (name of the valve suggests 15 seconds required)




250 posts

Master Geek
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  Reply # 2105610 10-Oct-2018 14:12
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I had been thinking about that too because once the roof cools it turns ALL the power off so what it left to power open the valve?!
Could this Trade Me unit take a second 12VDC supply to overcome this?
Thanks




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  Reply # 2105652 10-Oct-2018 15:11
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stuffed: I had been thinking about that too because once the roof cools it turns ALL the power off so what it left to power open the valve?!
Could this Trade Me unit take a second 12VDC supply to overcome this?
Thanks

 

Yes you would feed a second 12VDC supply into that trademe relay.

 

I think that the cost of 2nd power supply + relay is probably approaching that of a diaphragm valve, and you have the uncertainty of whether your current valve will burn out if power is applied to it for (say) 8 hours at a time


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  Reply # 2105669 10-Oct-2018 15:40
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nickb800:

 

stuffed: I had been thinking about that too because once the roof cools it turns ALL the power off so what it left to power open the valve?!
Could this Trade Me unit take a second 12VDC supply to overcome this?
Thanks

 

Yes you would feed a second 12VDC supply into that trademe relay.

 

I think that the cost of 2nd power supply + relay is probably approaching that of a diaphragm valve, and you have the uncertainty of whether your current valve will burn out if power is applied to it for (say) 8 hours at a time

 

 

And there is still the issue that when the temperature in the collector drops to a particular value, the 230V AC shuts off, which is what would power a second 12v supply used to close the valve.





Mike



250 posts

Master Geek
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  Reply # 2105670 10-Oct-2018 15:41
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Thanks for your help and have ordered the relay. No probs about 12VDC transformers as have a box of them from local ex CCTV projects.
My old retired sparky mate may need a defibrillator though when show him what needs done!





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