- These LCD Writing Tablets are available a dime-a-dozen now a days some 100 INR or so, for the 8" variant. Its nice fun using them: for notes, reminders scribbling stuff, practising handwriting, doodling etc. A stylus is provided to enable writing on the device. A small CR2025 battery is used to erase/reset the written stuff all at once.
- One of the common problems with this tablet is that after a while, the erase function stops working and it becomes practically useless.
- A while ago I had attempted a similar exercise with another tablet and ended up ripping it apart and not able to fix it and hence had to discard it.
- Luckily this time this tab would erase contents only sometimes. Finally decided to open it up and see what the problem is.
- Basically the Li-on battery powers a small custom IC. Noticed that it gave some 3.3V.
- But after some experimentation realised that the IC is a boost voltage converter and for a tiny fraction of time it boosts it to a relative high value and then brings it down.
- Luckily I had such a module lying around and on powering it up using a supply I was able to get the erase to work flawlessly.
- Below is a video showing the action using the now defunct button and then the corrected action using an external circuit. This was pending since a long long time. A teeny bit of happiness that I could figure it out. This feature will be useful in other applications as well. Hopefully will use it when I get to that stage.
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