Got a new lamp for the desk and its touch-based dual light from Amazon Basics. Minimalistic design with an adjustable gooseneck. The “touch” button cycles through the LED modes and you can dim/ brighten the 40LEDs. It has a 18650 1200mAh cylindrical LiIon rechargeable battery with the BIS 16046 battery certification. It has a micro-USB port to charge the battery with an indicator light(which doesn’t work the way it’s supposed to as the assembly team tried to cut corners by adding only a single LED). The circuit contains battery protection ICs and a battery charger IC which charges at a max current of 350mA(Full Charge in 4hrs). It does contain an unnamed microcontroller which handles all those logic switchings. It’s probably one of those absolutely dirt cheap one-time programmable microcontrollers. The microcontrollers drive a couple of MOSFETs which are connected to the LEDs via a series of 1.6Ohm resistors to dissipate power over multiple 0805 packages.
The cool part is the touch circuitry. This is handled by a spring and 1kOhm resistor. When someone touches the spring, it acts as a capacitor with our body. I am guessing they are sending a square signal to this pin and reading it back based on the RC time constant with your body. Each capacitance change is measured as a button press. Neat setup. The base of the lamp also contains a large metal plate which acts as a counterweight to prevent the lamp from falling over. Overall a good buy for the price.
You can check out my Instagram reels section for a video of the lamp’s cool “spring touch” functionality in action.