DIY Upgrade SHARP CS-2122H Calculator
The SHARP CS-2122H VFD display calculator can only be powered by a 220V source, which is then converted to 27V and 5V AC via a transformer. This setup can be quite inconvenient. How can this issue be resolved?
One solution is to DIY the calculator to switch from AC to DC power.
After testing the original transformer’s output, which provides 27V and 5V AC, I modified the calculator to use a rechargeable DC power source. Here's how it was done:
The original 5V supply from the mainboard and a battery were connected to the input of a DC-DC boost converter.
The output of the boost converter was connected to the original mainboard point where the 27V AC (converted by the rectifier bridge) was fed.
The output voltage of the boost converter was set to around 21V, which allows for normal display functionality (tested to work between 14-27V, though higher voltages risk damage).
A battery protection board (with 1A output current) was used for charging. The battery has a capacity of 3600mAh, providing up to 6 hours of continuous display usage with all segments lit up.
Here's the summary of the modifications:
Boost converter
Charging port secured with hot glue
Long screwdriver needed
Final result
The final result
The switch added to the battery:
