Hi,

I have 3 of those and while they work quite OK, they just call to be controlled by something smarter, e.g. arduino or Raspberry PI.

The good thing is, they have a handy cinch connector. The bad thing is, I have no idea how to control them.

The only electronic part is bottom left. It seems to be an electromagnet. If I switch the unit ON, my cheap voltmeter reads a short burst of voltage topping about 6v (battery is 9v), and the current seems to be about 200mA. After this burst there's nothing. Switching it off reads nothhing, but the magnet pushes the black valve thingy way (it's centered over magnet when assembled). The interesting thing is, even if I switch it On and then disconnect the wires, it remains in that position, the magnet is holding it, even though there is nothing connected.

Any idea how to design a circuit to control it?

 

I made a circuit for an Ebay bought solenoid.

When the firetech at work refill the fire extinguishers, he is supposed to have 6L of water. Instead of marking 6L in a bucket and filling that with a garden hose, and then pour it into the extinguisher, I made a circuit, that when properly set, allows 6L of water flowing through. (Oooops where is Loosie when you need him. This was a long sentence.) Now the garden hose is put straight in the extinguisher, and the tech is pushing a button. I don't know if this helps, but have fun!

 

Doing some tests - I don't have good enough equipent to measure the current spike the circuit sends, but I'm pretty sure it:
- only sends a short burst, say about 1s or shorter to open the valve
- same for closing
- I can replicate opening by using 25ohm resistor in series with the valvle and
- closing by using 200 ohm resistor in series and reversing the polarity

does that make sense?

 

Doing some tests - I don't have good enough equipment to measure the current spike the circuit sends, but I'm pretty sure it:
- only sends a short burst, say about 1s or shorter to open the valve
- same for closing
- I can replicate opening by using 25ohm resistor in series with the valve and
- closing by using 200 ohm resistor in series and reversing the polarity

does that make sense?

Yes, because it is a latching solenoid. A forward current pushes (or pulls) the magnet to open the valve, which get latched open. A reverse current moves the magnet back to close the valve. Since a spring holds the valve close, less power is needed to close the valve than it takes to open.

 

Aaa.. so there is a permanent magnet involved and forces are either magnet + electromagnet or magnet-electromagnet? Plus the metalic part of the valve actually gets magentised and holds the valve open.

So controlling this with arduino should be quite simple I guess. I would need 2 relays per valve to be able to reverse the voltage /sung h bridge) and that's about it. Is there a better option?

 

Another question on how to power this… Ideally I want to control it over internet, so I'd need Arduino + wifi shield, which draws quite a lot of current. I have an outside power plug but I'd prefer to avoid using it as I don't know how to make everything safe.

However, I do have a basement window quite close to where I need Arduino. How crazy is it to use two coils - one on the inside of the window, which is connected to the mains, and one on the outside of the window, to power the whole thing? Will it burn the house down or would it be relativelly safe? sth like this http://www.instructables.com/id/Wireless-Power-Transmission-Over-Short-Distances-U/

Another idea might be using solar cells and a lamp, again through the window (or combined with sun, why not).

 

Here's a circuit which could provide pulses of opposite polarity under Arduino control:-