Was trying to figure out why a Vacuum called Electrolux ErgoRapido ZB3012 is not working. Found that there is a likely issue with the button controls and found that there is some replacement board in:

Also found this youtube video useful https://www.youtube.com/watch?v=38R1_EWN77s

Using these above clue I was able to give my best guess on the design and sketch up the schematic

You can open it as a pdf or dxf or download the KiCAD Schematic

Overall the key insight is:

  • The button control consist of two wires, where different resistance is applied to trigger different button press.

    • 1kohm resistor: Power Up/Down Toggle
    • 4.7kohms resistor: Power On/Off Toggle

  • Charging indicator

    • I don't fully understand this, but i suspect it's using a BJT to control the power going to an indicator led that is triggered only if current is flowing from the power input to the battery charger terminal.
    • This appears to be dropped in the name of reducing product cost over time, but there was no incentive to change the design.

I've logged it to the schematic above regardless of if it's of use (or my reverse engineering correctness) currently as the design process is still interesting. Especially the use of resistors to indicate multiple different buttons, which is kind of what some wired mobile phone headphones are doing.