Infrared Remote and Battery management PCB

I got into this project when my wife was looking into remote shutter control for her Nikon DSLR. Nikon charges a pretty penny for a remote ($25!) so I grabbed a Garbduino board, a crappy amazon IR LED and wrote some quick code with the help of this blog post - it worked! But there are a lot of Nikon owners in my life, so I figured I'd use this as a chance to get ahead of birthday gifts for 2021. I ordered 30 boards (I know, a lot of faith to put in myself on a first spin..) for ~$40 on JLCPCB, including SMT assembly. Including other parts (good IR LED, batteries, etc.) the total cost for all 30 boards was ~$100.

Parts

IR LED It is crucial to get one with a narrow beam angle if you want range - this one has a 10 degree beam angle, which is narrow enough. This is also a high-power LED, accepting up to 100mA of constant current and up to 1A 'peak'. Reading the datasheet shows how duty cycle over a period of time relates to recommended max current. For my purposes, 100mA is fine - but since I couldn't ge the exact resistor I needed for my LED current sink to draw 100mA, I upped it to ~120mA, which is comfortable given the duty cycle.
500 mAh Batteries I use ebay for batteries when I don't need to draw a lot of current. I wouldn't use these for high-current stuff probably, since they don't specify a C value. But for $2 a piece, I love them for general-purpose applications

Full Schematic

There is not too much excitement in the schematic. I just followed the datasheets as far as the battery charge/protect part of the board, and otherwise it is basically a MCU, some buttons, a micro-USB charger, and a current sink. There was no need to boost the voltage to something constant for this circuit, since the current sink and MCU are fine at the battery-overdischarge voltage of 2.5V. I would prefer something higher like 2.9V for overdischarge, but this is what JLCPCB offers for battery protection ICs.

Download Design Files

As you can see in the video, the remote works beautifully, and has a good range!

I left the program (UPDI) and GND pins accessible from the printed case so the code can always be changed in the future. I am considering making each button work for a different brand of camera: Canon, Sony etc. or using the 3 spares to control custom lamps and stuff around the house. Looking forward to getting my 20 batteries in the mail so I can gift these around. Will post all design files when I get time.