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.

Daniel