Inside a good rechargeable baseball cap work light (with schematic)

Unlike the other lights that clip onto the bill of a baseball cap, this one has the immense advantage of having angle adjustment. That means the light can be aimed exactly where you need it.
Add the fact it can be recharged with a USB cable and has a battery level indicator, and it becomes a very useful work light.
But there's more! Aside from the two intensity levels in normal use it also has an infrared proximity sensor so that it can be switched on and off by simply waving your hand in front of it. This is useful for when you're wearing work gloves or your hands are wet. The sensor can be sensitive to retroreflective material (hi-vis stripes) on other people's work clothing.
If that's not enough, the unit can be placed on a surface and aimed/angled to act as an area work light too.
The internal cell of this particular unit is rated 1000mAh and has protection, but I notice that other listings gave options of 600mAh and 800mAh. The true flashlight aficionado could upgrade their unit with a bigger cell. This one has the code number 803040 which means 8mm thick by 30mm by 40mm. A common cell size.
Here's a generic eBay search for these units:-
www.ebay.com/s...
Target price around $10, which is double what I paid earlier in the year - so it may be worth exploring keywords. The price increase may be due to popularity and will also have been affected by the new USA import charges. (Try searching on a local eBay site if not in the USA.)
I'm not sure if the microcontroller in the light is a plain unit using an internal voltage reference to monitor battery level, or if it is a microcontroller optimised for lithium cell powered products with integrated charge monitoring.
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