Inside a "toy" thermal printer (Patreon)

Published:

2023-09-02 14:41:08

Imported:

2023-09

Content

Very common on eBay and quite a fun device. It uses standard 58mm thermal paper on very small rolls (you can re-roll from a bigger roll though) and also prints on thermal label material as a continuous strip.

The circuitry is as minimalist as you'd expect, with the bulk of the work being done by a bluetooth microcontroller and the driver in the printhead itself.

The bits that added to the complexity of the reverse engineering were polarity reversal detection and the clever power activation section where the microcontroller can literally turn itself off completely.

https://www.youtube.com/watch?v=4dRGZEcAp38

Files

Mini bluetooth thermal printer teardown - with schematic

These are really cheap and common devices on eBay, sold as toys for printing images onto thermally sensitive paper. This one came with several rolls including coloured paper and self adhesive label material. The printer can only print one colour, usually black, dictated by the paper itself. The app does allow printing of photos, and uses dithering to get rough shades of grey. Given the relatively low resolution, the images are surprisingly identifiable. The thermal printers are very minimalist and refined due to their widespread use in receipt and label printers. If you consider that almost every till has a thermal printer for ease of maintenance (no ink) and an absolute minimum of moving parts, then it makes them very cheap and available for items like this one. The printing is done by heating up the paper with a row of tiny resistors. When heated the thermally sensitive paper changes colour. Although the USB data lines are there, I plugged the printer into the USB port of my Chromebook and it didn't detect it. It may work with a PC. If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty. #ElectronicsCreators