Add wiring.md

wiring.md

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+# Wiring
+
+## Sensors
+
+DS18B20 pinout:
+
+| PIN | Use  |
+|-----|------|
+| 1   | VDD  |
+| 2   | GND  |
+| 3   | DQ   |
+
+# Notes
+
+## Solid state relays
+
+The SSRs draw 5-7 mA when supplied with 3.3 V.
+
+## RPi
+
+A maximum of **16 mA per pin** with the total current from all pins not exceeding 51 mA.
+
+## DS18B20
+
+A DS18B20 temperature sensor draws up to 1.5 mA. It requires approx. 750 ms to convert at 12-bit resolution.
+
+The DQ line must be pulled up by a 4.7 kohm resistor and connected to GPIO4.
+
+The kernel needs to be configured via `/boot/config.txt`:
+
+```
+dtoverlay=w1-gpio-pullup,gpiopin=4
+```
+
+1-Wire drivers need to be loaded in order to create the connection between the physical sensor and the rPI.
+
+```bash
+modprobe wire
+modprobe w1-gpio
+modprobe w1-therm
+```