Hello,

Is the resistor getting warm/hot?
What is the power rating of the resistor?

Bertus

I have two power resistors in parallel, giving me a resistance of 2.2R ... each having a power rating of 11W... They aren't really heating that much cuz their power ratings are so high I guess

 

Hello,

Is the resistor getting warm/hot?
What is the power rating of the resistor?

Bertus

I noticed a difference between the load voltage and the voltage between the adjust and the output... even the they are connected to the same terminals I found a difference of 0.4V almost.....
Turned out it's the jumper wires when I connected everything directly there was no voltage loss.... is this normal??
or is it because of the heat that the resistance of the wires increased?

 

Measure the voltage at all the nodes in the circuit and post them here.

 

And post the COMPLETE circuit with the load included.

 

I made a very simple circuit as in the attachment
It's supposed to output 625mA, but only outputs 500mA in actuality....
any insights as to why this is happening? is it a reasonable marginal error?
I tried decreasing the resistance such that an output of 825mA is expected but only reached around 600mA...
I actually want it to reach it 1.2A, but at this rate it seems highly unlikely....

Thanks for the help

IME: The published ratings are a little on the optimistic side. Also a variable regulator set to low output voltage has most of the voltage across it - your heatsink may not be man enough for the job and the thermal shutdown could be pulling in the reins.

Many data sheets and application notes for the fixed 3-terminal regulators; show examples of adding an external pass transistor for more current.

There have been product bulletins for SMPSU 3TRs that can deliver more current, but not sure about variable types. They've done their best to make it the same size - but it is a little bulkier.

 

The LM317 is rated for 1.5A minimum so it should be able to do 1.2A with a proper heatsink.

 

The LM317 is rated for 1.5A minimum so it should be able to do 1.2A with a proper heatsink.

Should and can are often 2 different things.

I tend to rate with a big safety margin unless its a quick lash up to do one job and get slung back in the junk box.