Melon Green is open source in terms of software and hardware. You can freely make your own board using Circuit Diagram and/or PCB Layout which are included in M.G.'s repo.
Next step is to Upload M.G.'s operating software to board's AVR.
Melon Green's Circuit Diagram, PCB Layout and some useful information about electronic parts can be found in Melon_Green_vx.x.x.fzz files at the repo's root (last version) or Board Revisions folder.
.fzz project files are created by free and open source electronics CAD application, Fritzing.
Melon Green v1.2.0
The board has seven functions (relays), but feel free to customize it. This one is a sample of simplified versions, made on a prefboard:
Total Board (v1.2.0)
| Amount | Part Type | Description |
|---|---|---|
| 1 | AVR (ATmega328) | ATMEL ATmega328/p (DIP) |
| 1 | Crystal | 16 MHz |
| 2 | Capacitor | 22pF Ceramic |
| 2 | Capacitor Polarized | 10uF Electrolytic |
| 2 | Rectifier Diode | e.g. 1N4007 |
| 1 | Pushbutton | Tactile [Reset] Button Switch (4 or 2 Legs) |
| 1 | Voltage Regulator | e.g. L7805, output voltage: 5V |
| 1 | SPST Switch | Power Switch |
| 3 | Male pin header: 1*2 pins | 1*6 ♂ male: DC power, Battery Connection, Relays Ext Power (or Power Jack) & DebugMode Jumper (or switch) |
| 2 | Male pin header: 1*3 pins | 1*6 ♂ male: Internal/External Power for Relays Jumpers |
| 6 | Socket or Pin Header: 3*1 pins | e.g. 1*18 ♀ female. for Serial (Tx Rx Gnd) port & Sensor Connectors |
| 1 | Pin Header: 4*1 pins | RTC Module Connector |
| 1 | Pin Header: 3*2 / 6 pins | [USBasp] Programmer Connector |
| 7 | 3 Pins Screw terminal | For 7 Functions (Irrigation, Grow Light...) |
| 10 | Basic Color LED | Optional Colors (e.g. 2 Yellow, 1 Red & 7 Green) |
| 7 | Optocoupler | Optical Isolator like: TLP621 / PC817 / EL817 |
| 1 | TRANSISTOR_NPN | 2N2222 |
| 1 | TRIMPOT | 1-10 KΩ (LDR Variable Pull-Down Resistor) |
| 4 | 10kΩ Resistor | tolerance ±5%; 1/4 - 1 Watt |
| 10 | 220Ω Resistor | tolerance ±5%; 1/4 - 1 Watt |
| 7 | RELAY | For 7 Functions (12v SPDT) for connecting High Voltage Equipments |
| 1 | 28 Pin DIP/ZIF Socket | (Optional) To place the AVR on the board safely |