LM317T voltage regulator

I breadboarded a voltage regulator using the LM317T (69p from Maplin) and various reclaimed components. The aim was to power one of the Poundland "Camping Lights" in its original all-the-LEDs-in-parallel form. The breadboard is a bit of a mess as to the right is a simple zener diode and two transistor voltage regulator; to the left are various old projects which I couldn't be bothered to remove. Using two fixed resistors and a variable resistor between them, with the slider connected to "Adj" on the LM317T, I achieved an output voltage of between 2.1V and 4.4V, exactly what I wanted to feed the LEDs.

I took a few measurements of current and voltage applied to the 24 ultrabright LEDs in parallel:

3.0V across LEDs; 0.13A drawn (power = 0.39W)
3.5V across LEDs; 0.70A drawn (power = 2.45W)
4.0V across LEDs; 1.43A drawn (power = 5.72W)

Any less than 3V and the LEDs weren't bright enough; any more than 4V and I was worried that they'd burn out. As it was, with 4V across them the LM317T was getting very hot, even with the (admittedly small) heatsink. It's rated at 1.5A, so it was running close to the limit.

If I knew how to draw circuit diagrams on the 'pooter I'd draw it.

In the next post I'll describe the LED dimmer I built (from the excellent Renewable Energy UK website).