LED string with timer and printed case

Christmas is coming soon. Take one of these simple battery operated led strings. Mine was from IKEA. You get a nice red battery case, a power switch, a resistor, and a string of 10 red leds with cabling. No way you could source alle these components on your own for less or quicker - unless you are planning to build a 3 digit number of these and break it down.

Anyway, I didn't like the simple on/off switch. Sure, I can switch it on in the evening, but I can't be bothered to remind myself to switch it off before going to bed. A timer was needed.

Nowadays, everything is powered by microcontrollers, why not a simple battery led string as well...

The timer circuit is an ATtiny45 microcontroller, which is cheap, doesn't need many external components and was what I had at hand. See the last picture for the schematic.

The timer circuit does not have an on/off switch. The reset button starts the operation (timer function). After a programmable amount of time (see config.h - anything