In this post I try to give an estimate of the costs for building the device.
Costs
This is a rough estimate of the costs for the project. Passives and minor parts not included.
Controller board:
| Reference | Value | Qty | LCSC Part | Price € |
|---|---|---|---|---|
| SW1 | SPDT switch | 1 | C388633 | 0.46 |
| Y1 | 8MHz/12pF | 1 | C2682775 | 0.15 |
| U6 | STM32F446RETx | 1 | C69336 | 6.9 |
| U4 | CAT24C256 | 1 | C6482 | 0.3 |
| U3 | REF3025AIDBZR | 1 | C11334 | 0.3 |
| U1 | TP4056-42-ESOP8 | 1 | C16581 | 0.8 |
| IC1,IC2 | TPS63802DLAT | 2 | C1849531 | 3.2 |
| PCB | From JLCPCB | 1 | 10 | |
| Battery | EEMB 3.7V 1100mAh LP603449 (Amazon) | 1 | 12 | |
| TFT | EQV 2.8“ 240×320 capacitive touch screen, Ali Express | 1 | 12 | |
| 46.11 |
Relay board:
| Reference | Qty | Value | LCSC Part | Price € |
|---|---|---|---|---|
| Diodes | 98 | 1N4007W | C2944153 | 0.4 |
| Driver ICs | 6 | TLC59284DBQ | C130209 | 4.2 |
| Relays | 49 | TQ2-L2-5V | C1525303 | 44 |
| PCB | 1 | From JLCPCB | 10 | |
| 0.1% Resistors | 48 | various | ~4 | |
| ~52 |
With parts sourced from LCSC and the PCBs manufactured by JLCPCB the project can be built for around 100€ (taxes and shipment not included).
Enclosure
I could not find an enclosure in a format which would fit the assembly so with a hacksaw and a bunch of files I built my own using a piece of 1.5mm aluminum sheet metal. The results of my efforts can be seen above.
Build it Yourself
You can build the project yourself using the fabrication data provided for download below. The archive includes schematics, Gerber files and firmware.
