Rechargeable Batteries

Rechargeables have a lower voltage (1.2v) than throw-aways (1.5 v).
However, this doesn't make any difference to us, as we'll build our circuits to use the lower voltage.

We hope that you have already chosen to switch to rechargeable 'AA' batteries, rather than throw-aways, for a host of environmental reasons too obvious to mention. If you have a problem with rechargeables and absolutely must use 1.5v throw-aways, you will need to re-calculate the resistance used in each circuit, otherwise your LEDs will have a significantly shorter life-span...

... as will the planet.