Rob's Dimmer Control (schematic)

This is the second control circuit tried, and it actually works, so that's a plus

Most of what you see here is for a nice low battery warning feature which will 'blink' the main lights about 4 times a minute when the battery is getting low. The plan was that there would be a complete cut-off a little later. Cunningly though, this complete cut-off caused a feedback effect and actually meant that the lights dim very nicely as the battery discharges.

If you're not interested in this warning the only stuff of interest should be the 270+500 trim and 470+1K trim resistance networks and switch between them. If you don't want dimming of course, forget that part.

See Rob's Homemade LEDs for more about this.