In Part 1 we worked out what it is we want to make, why it needs making and we ended up with a basic circuit. In Part 2 we learned about Solenoid valves and delved into the Arduino code that will make it work.
Now in Part 3 we will look, briefly at the circuit board.
Below is an image of the topside of the finished circuit board. In the middle you will see an Arduino Micro and an Adafruit Power Boost 500 (Basic). These two together provide the logic and the power. The are flanked on both sides by first a row of N-Channel MOSFETs and then a row of 3.5mm screw terminals.
This next image shows the unfinished (and in some areas embarrassingly soldered) bottom side of the board.
My board in its original form was not connected like a breadboard, which was a rookie mistake, but I managed it, eventually. . . and by eventually I mean, 7 hours later.
Terrible soldering aside, here you can see the pins from the Arduino coming through the board and, obscured slightly, the pins from the Power Boost 500. Later, the Power Boost’s 5V and GND pins will connect to the Arduino’s VIN and GND pins.
You can also see some diodes. These are kickback protectors. I wasn’t really sure if they were actually necessary in the grand scheme of things, but I decided to err on the side of caution, and considering they were very cheap, I thought little of it.
The important thing to note here is the Brown wire soldered to the large pads at the bottom of the image. This is the GND wire from the 12V Battery and it is connected also to the Arduino making it a Common Ground. At the opposite side of the board is a Red wire soldered along the large pads. This is the 12V Line and is connected only to the screw terminals and the Cathodes of the Diodes.
I describe how the circuit works, and more importantly how the MOSFETs work in Part 1, so I shan’t go over it again here.
Eventually I managed to wrangle the board into shape, and ended up with something that looks this:
Here you can see that the Arduino’s digital pins are fully connected to the MOSFETs, and the large Red and Black wires are connecting the PowerBoost’s Power and GND pins to the Arduino.
With the board completed it was time to test. I tweaked the code so that the pins would only be high for 10 seconds or so and the programme would run through more than once, and got out the multi metre.
Satisfied that 12 out of the 15 outputs were working I decided to call it a day. Seven hours of continuous soldering gave my really bad eye-ache. Instead I quickly soldered a capacitor and a JST cable onto an Adafruit DC / USB / Solar Lithium Ion / Polymer Charger and retired with a beer.
A 3.7V LiPo battery will be plugged into the left-most JST jack on the solar charger. A 6V Solar Panel will be plugged into a DC barrel jack hidden behind the capacitor and the circuit board’s Power Boost 500 will connect to the JST jack attached to the Red and Black wires. This will allow us to run the circuit board entirely off of renewable – and most importantly – free energy.
In Part 4 we will look at the Solar System . . . so to speak.