I didn’t really think about the BOM cost of my programmable decade resistor until I was asked. Then I also wanted to know. It is fairly difficult to put a number to what I paid, since I had a lot of components left from other projects that I could use. This includes not only cheap chip resistors and MLCCs, but also connectors etc.
Normally I order from both mouser and digikey, but for some of the industry-standard components, connectors etc I use local distributors. This is why I’ll only give a very rough estimate for the per unit costs including taxes (not including any shipping costs). For some of the parts like the PCBs there is a minimum order quantity that will increase the cost in most DIY scenarios.
Mechanical parts
| # | Description | € (est.) |
| 1 | ELMA Stylebox 15 Standard (not new) | 50,00 |
| 2 | Front & Rear panels (Aluminum PCBs) | 5,00 |
| 3 | Rotary encoder knobs and key caps | 10,00 |
| 4 | IEC power connector + Fuse | 3,00 |
| 5 | 4mm banana sockets | 8,00 |
| 6 | Connectors, cables etc. | 2,00 |
| 7 | Mounting hardware | 2,00 |
| 80,00 |
Mainboard
| # | Description | € (est.) |
| 1 | Mainboard PCB | 3,50 |
| 2 | STM32G441KBT6 | 6,50 |
| 3 | EC2-12NU relays (or similar) | 73,50 |
| 4 | Precision resistors | 63,00 |
| 5 | Other components | 30,00 |
| 176,50 |
UI Board
| # | Description | € (est.) |
| 1 | UI PCB | 2,50 |
| 2 | STM32L010 | 2,00 |
| 3 | STP16CP05 constant current LED drivers | 10,00 |
| 4 | LED displays | 15,00 |
| 5 | Rotary encoder and switches | 37,00 |
| 6 | Other components | 12,00 |
| 78,50 |
Power supply board
| # | Description | € (est.) |
| 1 | Power supply PCB | 1,00 |
| 1 | TRACO TMPW 10-115 | 19,50 |
| 1 | NE-18 series power switch | 8,50 |
| 1 | Other components | 5,00 |
| 34,00 |
Conclusion
According to this calculation the total cost of the unit would be about 369 €. Quite a lot, actually. This doesn’t necessarily reflect what I paid for it though. One example: I bought 5 NE-18 type switches on ebay for about 2 € each. These are not necessarily the same as the ones provided by mouser, but both variants could be used.