1.2 KiB
Arduino valve
This is an example how to open/close a Gardena Water-Valve (the ones that use a +9V block battery for power). Note that we used the L293D Dual H-Bridge circuit which needs +5V for power supply (while the Merkur-Board uses 3.3V) but it can use 3.3V inputs directly from the Merkur-Board without a level shifter. So it's probably a good idea to use some other H-Bridge circuit that can also use 3.3V. An advantage of the L293D might be that it can be used for two valves simultaneously (with the second, currently unused H-Bridge).
We provide the schematics of our breadboard-design in valve-breadboard.png -- as noted above it's a good idea to use a different H-Bridge circuit.
Also note that one of the pins we use in the software for signals to the H-Bridge (D4) is also used for the LED on the Merkurboard. The LED is on when the H-Bridge is off. This was nice for testing the breadboard circuit but should be changed for a real deployment to save power of the battery. It is also probably a good idea to turn off the power-supply of the H-Bridge with an additional MOSFET depending on the power consumption of the H-Bridge you're going to use.