5 years of watch development in one master piece of hardware:
Features:- BPW34 solar cells, plastic, small, unbreakable
- Ultra High effective step up converter 95% with minimum 0.4V working voltage
- MAX1724 - Thanks for samples from Maxim Integrated
- custom LED 4014 display, inspired by https://hackaday.io/whygee https://hackaday.io/project/8693-dypled project
- Supercapacitor capacity gauge
- Supercapacitor can be charged with USB (less than 3 minutes) or SUN (more than 5 hours)
Using high voltage 3V 5F supercapacitor from VINATech Co Ltd. (Thanks for samples!) super dimensions 25x8mm. 5F is for about 5 minutes in highest brightness and 20 minutes in lowest. In standby about 7-14 days.
DetailsFirst, a big thanks to Yann Guidon for eagle library for 4014 LED, and a great idea with DYP LED project.
I understand that these are not practical watches. I'm calling my product "party watch," not for daily usage but good eye catcher on special occasions. Standby time is acceptable, in good condition more than 7 days. If anybody thinks that 5 minutes run-time is low? It is abut 300 seconds if you display time for 3 seconds you can check time 100 times or 350 times in low brightness.
Charging:Charging is very simple because vinatech scap are 3V. I used 3V fixed voltage LDO MCP1700T3002ETT with 10R resistor to limit charging current + shottky diode for protection reverse current to LDO. The charging voltage drop to acceptable 2.95V.
Discharging:Heart is fixed 3V version of MAX1724 extremely low 1.5µA quiescent supply current Step-Up DC-DC Converter which can work until 0.4V imput voltage. I can use about 87% of stored energy. In all operation time I have stable 3.001V for MCU. I also have on board space for newest MAX17222, 300nA Iqc but I am unable to solder 6-Pin μDFN. Average consumption is now about 7uA.
MCU:I am using PICOPOWER Microchip/ATMEL ATMEGA328 standby consumption with running RTC is 0.9uA. Every second MCU wakes from sleep for add second to counter, and flash LED on gauge to show remaining capacity level. If you press the button you can show time, long hold adjust time. I am satisfied with the results. I have something unique in the world, non-practical but unique.
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