Help with a DPDT switch?

Forums › Gadgets, robotics, home automation, electronics (including wearables) › Help with a DPDT switch?

stuffed

271 posts

Ultimate Geek

# 242646 7-Nov-2018 11:27

I have a Double Pole Double Throw (DPDT) switch that am told that need to control a motorised 12VDC 40mm valve for my swimming pool.
It works with polarity one way to close and reverse polarity to open.
Ok have 2 x 12VDC supplies.
Can someone help me please as how to wire the 8 terminals on the switch?!
Very many thanks

Why work on Wednesday and stuff up 2 good long weekends

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1906 posts

Uber Geek

# 2121473 7-Nov-2018 12:29

One person supports this post

That’s a relay

stuffed

271 posts

Ultimate Geek

# 2121483 7-Nov-2018 12:40

https://www.trademe.co.nz/Browse/Listing.aspx?id=1793925351

Why work on Wednesday and stuff up 2 good long weekends

trig42

Banana?
4855 posts

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# 2121518 7-Nov-2018 12:49

It's definitely a relay, not a switch.

From the TradeMe listing:

Whats Shipped
1 x Relay LY2NJ DPDT 8 Pin HH62P JQX-13F With Socket Base

DPDT switches are just switches that switch both the + and the - (in DC) or L and N in AC.

A selection on AliExpress here.

stuffed

271 posts

Ultimate Geek

# 2121525 7-Nov-2018 13:06

Ok you guys - this was the post that I followed:
https://www.geekzone.co.nz/forums.asp?forumId=73&topicId=241065
If that unit (relay or whatever) that I lashed out and spent a whole $12 on is not right as was advised - what is?!
Need to get something in NZ - now.
Remember it is so that the valve closes via 230VAC turned on to 12VDC and opens on reversed polarity when the 230VAC turns off.
Thanks

Why work on Wednesday and stuff up 2 good long weekends

Gordy7

876 posts

Ultimate Geek

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# 2121526 7-Nov-2018 13:09

One person supports this post

Based on your original specs and the picture of the relay.... here is a quick schematic...

Gordy

MadEngineer

1906 posts

Uber Geek

# 2121658 7-Nov-2018 16:27

Just be aware with that circuit, in reverse polarity that diode will be conducting and the relay will have 0.7volts across it.

Gordy7

876 posts

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# 2121745 7-Nov-2018 18:43

2 people support this post

MadEngineer: Just be aware with that circuit, in reverse polarity that diode will be conducting and the relay will have 0.7volts across it.

You are quite correct. When the switch is closed the diode will be reversed biased and the relay coil will have 12 volts across it. When the switch opens the back emf (fly back voltage) of the relay coil will make the diode forward conduct preventing arcing across the switch.

Gordy

andrewNZ

2129 posts

Uber Geek

# 2121754 7-Nov-2018 19:00

You're saying the valve is 12vdc and you want to control it with 230vac. Is that correct?

If so:
1) Your relay will not work. It will go bang.
2) The above diagram will work but do NOT put in the diode.

There is possibly a solution involving the gear you have, you need to tell us what your control concept is.

Location: Dunedin

Gordy7

876 posts

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# 2121760 7-Nov-2018 19:20

The OP's spec is changing. Originally DC was specified. Now AC is a requirement.

Hopefully the OP will get an idea of how to apply a DP change over relay to his application.

Gordy

Bung

2996 posts

Uber Geek

# 2121781 7-Nov-2018 20:08

One person supports this post

andrewNZ: You're saying the valve is 12vdc and you want to control it with 230vac. Is that correct?

If so:
1) Your relay will not work. It will go bang.
2) The above diagram will work but do NOT put in the diode.

There is possibly a solution involving the gear you have, you need to tell us what your control concept is.

If the OP had kept to his original thread it would have been easier to understand. The 230vac powers a 12v plug pack turning relay on. 2 power supplies are used because the valve needs time to complete an open or close cycle after the relay loses power.

MadEngineer

1906 posts

Uber Geek

# 2121794 7-Nov-2018 20:36

OK, after reviewing everything, this dodgy valve that you've purchased from aliexpress opens and closes by reversing the polarity connected to "RD" and "BK". The spec sheet listed specifies 12 volts for 15 seconds to completely open or close the valve. It also weirdly specifies "DC5V/DC12V/DC24V, AC110V-230V". I don't think that's correct (edit, probably is referring to whatever relay or control circuit you're using to drive the "actuator"). Ignore it as twice on that page is specified 12volts for 15 seconds.

You're going to need a timing circuit and another power source. That relay would be useful for switching the polarity (wired as a poor-mans H-bridge) for toggling between opening and closing the valve. This relay isn't for turning the thing on or off.

"Solar unit turns on (230VAC) when roof water warm enough. Powers on (12VDC via transformer)" [quoting OP]
Relay switches to 'close valve' position
Power (DC12V) is applied to valve in the polarity set by the relay
Wait 15 seconds
Disconnect power to valve
(Wait until ...)
Solar unit turns off
Switch relay to 'open valve' position
Power (DC12V) is applied to valve in the polarity set by the relay
Wait 15 seconds
Disconnect power to valve
(Repeat)

(edit, "Solar unit turns off when roof water cooler. Ok how to get a burst of power to open the motorised valve?!" suggests to have valve closed when water is cool)

That's the basic flow chart. Of course the relay switching steps only apply if its current status needs changing but that comes down to how you wire it.

You wire the relay on the normally open or normally closed position to suit which ever case the system is going to be sitting in the most so that the relay is driven for the least length of time.

nickb800

2298 posts

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# 2121802 7-Nov-2018 21:04

Despite discussion in other thread, OP wants to apply power to the actuator all day until the sun goes down, as the product suggests it can handle that. I think this will work for a short time before the actuator dies.

My original suggestion which I stand by is to get a diaphragm valve activated by solenoid which is designed to have power applied for an extended time, and doesn't need a circuit to control closing.

gregmcc

1716 posts

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# 2121811 7-Nov-2018 21:37

you will need a couple of limit switches at the end of fully open and the end of fully closed in order to turn the motorised valve off otherwise the motor will keep on running against the end of travel and eventually burn out

Bung

2996 posts

Uber Geek

# 2121860 7-Nov-2018 22:48

I don't know what valve the OP has but you can get valves that have self contained switching to switch power off motor once fully open or closed and wait for reversed polarity.

MadEngineer

1906 posts

Uber Geek

# 2121864 7-Nov-2018 22:50

Gregmcc, have another look at his relay and posts. 230 volts will smoke it.

OP needs to hire a pro instead of throwing money onto junk. It will be a case of throwing money into a hole in the back yard better spent on someone that knows what they’re doing. I see it everyday - people buying stuff like this when by the end of it they could have hired someone that knows what they’re doing that gets the right gear at a price so much cheaper that the difference pays for the labour. Unless of course you’re doing it for fun but then you wouldn’t be asking here.

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