You can get a step-up voltage converter to convert the USA 120V to UK 220V. But you may find it's easier and/or cheaper to just buy another power adapter for...

Try a Google image search for NiMH discharge curves to get an idea of what you're looking at: <a href="https://images.google.com/images?hl=en&rlz=1B3GGGL_en___CA230&q=NiMH+discharge+curve&um=1&ie=UTF-8&ei=W-5VS9TyHpTAsgPG49EU&sa=X&oi=image_result_group&ct=title&resnum=4&ved=0CBkQsAQwAw" target="_blank" rel="nofollow noopener noreferrer">NiMH discharge curve - Google Search</a> -...

I agree you will need a heat sink. A 12V to 3V linear regulator system will likely get hot at any appreciable current. You can get high-frequency buck converters that...

Newer PICs may be better. Old ones used to drop a lot of voltage when sourcing current.

* PIC16F688 is it a microcontroller or a microprocessor ? Most people would call it a microcontroller, because it is designed to connect directly to other devices to do "real"...

Good posts. In my experience, PICs do better sinking current than sourcing. I would recommend connecting the LEDs so that the PIC sinks the currents. - CG #-Link-Snipped-#

Track width will vary according to the power being run through the track and the capabilities of your PCB manufacturer. Usually 10 mil is fine for most low-power stuff, but...

It will decrease. No battery provides a perfectly consistent voltage over time. As a general rule, rechargeable types will provide a 'flatter' discharge curve than non-rechargeable types. Battery voltage will...