On Thu, 17 Apr 2014 13:42:41 +0100, Daniel wrote:

On 16/04/14 22:23, Uncle Peter wrote:
On Wed, 16 Apr 2014 13:01:00 +0100, Daniel
wrote:

On 16/04/14 06:11, Uncle Peter wrote:
How easy would it be for me to change the current rating of a constant
current supply? One from a CREE LED light fitting, which I think is
very roughly 0.5 amps at 7V. I want to lower the current, the voltage
is ok.

My memory of teaching Power Supplies (about 15 years ago), the constant
current was maintained but keeping the voltage developed across a
particular resistor constant, so, in theory, by increasing the value of
the resistor, a lower current would develop the same voltage across the
sensing resistor.

However, you would have to determine which resistor and which value
.....!

Thanks for the tip, I'll run it on a bench with a dummy load and test
some resistor voltages, then try changing one a little.

If you've got a circuit diagram of your power supply, and you can
determine which resister is the "sensing" resister, replace it (for the
time being) with a variable resistor/rheostat in the same ohmic range as
the sensing resistor until you can determine what value resistor you
want to stick in.

This is a partial drawing of the circuit diagram of the power supply. I can't see half of the circuit connections as they go underneath the unknown microchip!
http://petersphotos.com/temp/PSU.jpg

--
Some "chinese english" instructions for an automatic light switch, needless to say I did not attempt to follow them during the installation....

The surface design is facility, comely but not losing generosity, it will not have accidented feeling after installation.
Wide working voltage: you will not be worried when you go all over Europe carrying it.
You could fix the sensor with two screws on the junction box in circular one, also fix it with special installation shelf.
In a word, whether the junction box installation orientation is true, it makes the installation flatly.
The lamp will be on automatically when you knock at the door or say "I am coming back".
It will make your home warmer and more romantic.
Penetrate the setscrew into installation hole, block on radiator to aim at the installation hole on connection box.
Let electrician or experienced human install it.
The unrest objects can't be regarded as the installation basis-face.
Don't open the case for your safety if you find the hitch after installation.
If there is any difference between instruction and products, please give priority to product, sorry not to inform you again.