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constant current

Advice on these Chinese DC - DC converters?

SO, I got a couple of these 80w DC - DC buck converters to supply power to Houston.  One is going to be the 5 volt supply for the servos, the other is going to be a 7.2 volt supply for the Rover 5.  Last night I got a motor out and adjusted them to the proper voltages.

The thing that's got me confused is the "constant current" part.  There are two multiturn pot type adjustments.  When I ran the motor, it pulled about 350ma turning the current pot didn't seem to change anything.

Luxeon Leds - what would be the simplest constant current driver for them

led5.jpg

I have just bought 5 of these 3W High-Power LEDs 

I could drive them off batteries direct ....

...however i would prefer to feed them with a "constant" but adjustable (350mA-750mA) current.

 

What would be the simplest circuit i could use ?.....

.... and would there be a way to PWM them?. 

 


Specs :-

3W High-Power White (6000-7000K) 130 Lumens - 140 deg