“I am repeating myself lately but here is yet another thermochromic project because I really like the effect of these liquid crystal sheets. This time I wanted to make a large clock that you can hang on your wall. The clock uses a 4-digit 7-segment display with the hours and minutes arranged vertically with a slight offset. Each segment consists of a PCB heater that is covered with a thermochromic liquid crystal sheet that changes color when the segment is heated.
Supplies:
- 28 pcs, custom segments PCB
- custom controller PCB
- 350x450mm thermochromic liquid crystal sheet, 30-35°C
- 280x350x20mm aluminum frame
- 280x350x2mm black anodized aluminum plate
- 56 pcs, PCB spacers, 5mm
- 28 pcs, JST PH to Dupont cable, 30cm
- 5V, 5A power supply
A detailed BoM can be found on my GitHub account.
You will also need
- SMD soldering equipment
- 2K epoxy glue
- exacto knife
The PCB that is controlling the segments was also designed in KiCad. It is based on a WEMOS D1 mini ESP8266 board and uses 74HC595 shift registers that are connected to n-channel MOSFETs to heat the segments. The segments are connected to the controller PCB using common male pin headers. I also included a DS18B20 temperature sensor so that the heating power/time can be adjusted according to the ambient temperature which is something I learned from my previous thermochromic projects.”