'On air' meeting sign for remote work

thingiverse

My brother is remote working and his office's hall is very dark, so whenever the door is closed (which is most of the time) we can't see the 'do not disturb' hotel sign he puts on the handle. I've seen him getting frustrated at having to jump to the mute key so I made him a simple lighted sign. It's just a 100R resistor and 4 3mm red LEDs, connected to a SPDT toggle switch and powered by a 18650 battery removable from the bottom. I used a diffuser sheet from a scrapped LCD backlight so it improves eyecandy and visibility. Needs 2x M3 screws, minimum length 4mm, and a battery holder ([these](https://www.aliexpress.com/item/33053366600.html) from Aliexpress are quite cheap and handy). Circuit is mounted on a 20x70mm perfboard. Faceplate, battery holder, difusser sheet and board are glued with cianoacrilate glue (Loctite). Stick it with double sided tape, et voilà ;) **NOTICE**: Please use a protected battery cell, so you don't need to monitor its level in order to avoid overdischarge.