It was long time I was thinking to make a watch with Nixie tubes. I spent 6 months to think and look around how to make it, 3 months of a mockup on the table and first SW version to confirm the feasability of the power supply and the SW, then 3 months to make a first mockup with can be wear on the wirst then 2 months on PCB version...
The mockup version is still working well. I use it on regular basis, all was make by hand, with thin wires and no PCB.
I design the power supply, 180V, around the LT1935 and voltage multiplier.
The tubes are manage with FET transistors, multiplexed. I start to use B5870 but they are rare and expensive. I made another PCB for Z590M.
The CPU is as usual for me an PIC18LF2420, in SO package, working in 3.3V with low IQ regulator from TI.
Today, to see the time, I use an LDR and just passing the hand above the watch , or press the unique button, will display hour then minutes. a press on the button will display date and after, the battery level.
The time control, to save the maximum of energy was very complex as the sleep time is not accurate. Now, the accuracy is correct but not yet very good. The autonomy in standby is very good. Can stay weeks without recharge. with daily normal usage, it can stand more than 1 week.
The battery is a small LiPo battery, 180mA, the recharge through an USB plug and a Max1555.
The current testing version with with 3 PCB, one in the bottom for the power supply, one vertical for the CPU, the last one for the tubes.
The thickness is today 15mm, the casing is 45mm. I found a supplier to make wood casing which is nice, dark or light color. Some pictures of these casing on the shop:
The CPU PCB has some options not yet tested and need develop the SW:
- Add a real time clock PCF2129T
- Add a small backup battery
- Add a movement sensor to try to have the time by turning the wrist
This project is interesting but quite complex. all in SMT component but still manageable with the iron.
Several pictures about the progress of this project.