I bought a variable power supply, trying to use it to output a certain voltage BUT wants to limit current output too, which this thing is able to do.

What are the 3 little knobs for?
I can think one varies voltage but how do the other two knobs work?

http://www.ebay.ca/itm/120946709133

I think its explained towards the end of the page how to control both current and voltage (to charge a battery?)
------------------------------------------------------------------------------
Battery Use:

Make sure of the voltage and current of the battery you need to charge
Adjust the constant voltage potentiometer to make the output voltage same to the charge voltage
Potentiometer Adjustment Direction: Clockwise (increase), counterclockwise (decrease)
Use the multimeter in 10A current scale to measure output short-circuit current, and adjust the current potentiometer to make sure the output current to the expected charging current value
The charge current of transfer lamp is default 0.1 times of the charging current (constant current value)
Connected to the battery and try to charging (for previous 5 steps, module input terminal is connected to power source, output load is NOT connected to batteries)

 

For $5.00, I would have expected complete documentation. Have you contacted the seller?

Just guessing, but, a coarse and fine voltage and current limiting would seem fairly standard. You can either play with it connected to a 1k ohm resistor, you can reverse engineer the schematic from the circuit board to determine how it works, or you can hope someone else here has done it already and is willing to share here.

 

I wonder if these diagrams from a google search might help?

Cheerful regards, Mike

 

I bought a variable power supply, trying to use it to output a certain voltage BUT wants to limit current output too, which this thing is able to do.

What are the 3 little knobs for?
I can think one varies voltage but how do the other two knobs work?

http://www.ebay.ca/itm/120946709133

I think its explained towards the end of the page how to control both current and voltage (to charge a battery?)
------------------------------------------------------------------------------
Battery Use:

Make sure of the voltage and current of the battery you need to charge
Adjust the constant voltage potentiometer to make the output voltage same to the charge voltage
Potentiometer Adjustment Direction: Clockwise (increase), counterclockwise (decrease)
Use the multimeter in 10A current scale to measure output short-circuit current, and adjust the current potentiometer to make sure the output current to the expected charging current value
The charge current of transfer lamp is default 0.1 times of the charging current (constant current value)
Connected to the battery and try to charging (for previous 5 steps, module input terminal is connected to power source, output load is NOT connected to batteries)

Here's a video:

https://www.youtube.com/watch?v=DYf7qKuZF_I

 

One pot controls regulated voltage.

One pot controls current limit.

One pot controls when the "fullcharge indicator" light comes on. That defaults to (or should be) roughly ten times less current than the current limit.

So if current limit is set to 1A, then when the current finally drops to <0.1A the "fullcharge" light comes on.