Last year, my employer gifted all the employees a table-top-watch-cum-pen-holder. The time display is a 4-digit seven segment display. It is a pretty neat gift for a work-from-home setup. I recently found it and decided to use it.
However, as soon as I inserted the AA batteries and turned it on, I saw that a few segments would not turn on or would do so very intermittently. I suspected a dry solder at one of the connections to the segment display.
Repair This We Shall!
So, this is what the display looked like.
After scraping thru the false wood material and tons of glue, this is what the connection looks like to the display from the internal circuitry.
After re-soldering the connection of the display, I tried firing up the display again. A couple of segments were still problematic! Close inspection of the connector told me that the connector was not making good contact with the host circuit due to mechanical stress when the circuit is placed inside the body of the gift.
This is not acceptable, what is the point of a watch that can’t show the time properly!
Fix This We Shall!
I first confirmed that all the segments turn on by applying voltages to the connector directly. Once it was clear that there was some problem with the host circuit (never got around to pinpointing what it was :-/), I decided to replace the entire host circuit with an Arduino + RTC circuit. I also found that this is a common-anode display. This shall be useful when writing the software.
Some quick soldering later, this is what the setup looks like.
After checking that the display is being driven correctly, I added the RTC module with the backup battery to my PCB. A few minutes and lot of soldering mistakes later, this is what the PCB looks like.
The Arduino sketch that drives this system is located here – https://github.com/sckulkarni246/arduino-my-table-watch
Now, finally 11:47 shows up as 11:47 :).
Thank you for reading and stay safe!