#Opensprinkler bee how to#

#Opensprinkler bee how to#

Now at least I know understand this particular valve works, and this understanding will help me figure out how to get OpenSprinkler Bee to control this valve.

If you apply the same voltage and strength as before, it will start magnetizing the core the other way, thus the magnetic pole changes direction but the metal piece will still be permanently attracted!Īnyways, this is very interesting to me because previously I had no idea how latching solenoid valves work internally. Observing this mechanism, it became clear to me that ‘closing’ the valve basically requires de-magnetizing the core, and that requires just a short pulse of low voltage in the opposite polarity. This makes it possible for the valve to remain in the ‘open’ status without contiguously drawing current from the power source (which is unlike non-latching valves like 24VAC valves). The key in making this latching is that an impulse voltage can permanently magnetize the core, thus permanently attracting the metal piece. Conversely, when closing the valve, the metal piece is released and dropped to block the hole at the bottom, this supposedly allows water pressure to build up in the bottom chamber, thus stopping the water flow. It’s quite easy to observe that when opening the valve, the metal piece gets attracted (left picture above), this supposedly releases the pressure in the bottom chamber, thus allowing the water to flow through the valve. The top section contains, supposedly, a coil and magnet inside, and a small cone-shaped metal piece that can be attracted to the magnet or released. This is very similar to other valves I’ve seen. In order to figure out what’s going on here, I un-tightened a bunch of screws and opened up the valve.Īt the bottom of the valve is a pressure chamber with a spring. This is quite strange to me: how come closing the valve only requires such a short pulse and such low voltage? It’s pretty easy to notice the asymmetry here: while opening the valve requires a pulse of 250 ms and -7.84 voltage (this is roughly the battery voltage since my 9V battery isn’t fully charged), closing the valve only requires a very short pulse of 62 ms and very low voltage - 2.5V. So I connected a 33 ohm resistor to the controller as a dummy load, and there you go, now we can observe the control voltages and pulse lengths. I measured the resistance of the solenoid valve, which is about 35 ohm. Then it became clear to me that the controller is in fact actively sensing the existence of the valve, and would not send control voltages if the valve is not detected. Upon connecting the control unit to an oscilloscope, I noticed something strange: no matter how I press the on/off button, it’s only sending a very short (a few milliseconds) pulse, which cannot possibly operate the valve. On most solenoid valves I’ve seen, the two impulse voltage (of opposite polarity) are roughly the same, and that’s also how the OSBee circuit works. It’s pretty common that when operating latching solenoid valves, the control circuit sends an impulse voltage to open the valve, and another impulse voltage in the reverse polarity to close the valve. To figure out the issue, the first thing I did was to check how the control unit (1250) is sending out control voltages to the valve. This was reported by a German customer, and it caught my curiosity. The initial request to look into this valve was due to the fact that OSBee can’t seem to operate this valve correctly: it can open the valve but never manages to close the valve. Nonetheless, it’s an interesting case that helped me understand how these latching solenoids work. The whole assembly including the valve and controller unit are quite pricy (close to 100 bucks), so it’s not a very cost-effective solution compared to other brands.

On spec, it’s operated using a single 9V battery, and to use this valve you need to buy a Gardena 1250 controller unit. This valve is mostly sold in the European market and isn’t very popular in the US market. Recently when helping a customer, I came across an interesting case of how to control Gardena 1251 latching solenoid valve using OpenSprinkler Bee.