On Sat, 26 Apr 2014 10:43:00 +0100, Daniel wrote:

On 26/04/14 06:37, Uncle Peter wrote:
On Fri, 25 Apr 2014 10:57:47 +0100, Daniel
wrote:

Snip

Now, reduce the resistance to, say, 30 ohms to try to draw more current
from the supply (from Ohm's Law I = V/R so 12V/30 gives 0.4A. Does this
happen??

18 ohms, 8.55 volts. 0.475Amps
27 ohms, 12.45 volts. 0.4611Amps
36 ohms, 12 volts. 0.333Amps
47 ohms, 10.8 volts. 0.2298Amps
56 ohms, 10.7 volts. 0.191Amps
Open circuit, 12.73 volts. 0.000Amps

Not very "Constant Current"ish!! Mind you, not very "Constant Voltage",
either!!

I'd just guess a poorly regulated Voltage, Power Supply.

I guess I just treat it as a **** power supply and find a resistor to go with the smaller LEDs to make the current correct.

It and the 3 CREE LEDs only cost £3, so I guess I shouldn't have expected anything cutting edge. Mind you, that's maybe why the bloody CREEs died early! I had every one of the batch replaced under warranty, then couldn't be bothered the second time. Or then again it could be because the heatsink on the LEDs was too hot to touch for more than 1 second, which I would think was also uncomfortable for the LEDs!

--
Women do not snore, burp, sweat, or fart.
Therefore, they must "bitch" or they will blow up.