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Would this work as a constant current load since I don't have a high power pot? Is there a better way to do it?

schematic

simulate this circuit – Schematic created using CircuitLab

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You're loading the 1.25V output of the LM317 with a transistor- it won't work very well. It will burn the pot out if you turn it up all the way.

I assume you're trying to draw a constant current from V1.

One method is to use an op-amp such as 1/2 an LM358:

schematic

simulate this circuit – Schematic created using CircuitLab

With the values shown, it will allow a current from 0-1A to be drawn from V1. R1 will dissipate up to 1W, and Q2 will dissipate most of the rest of the power- up to 2.7W for the values shown.

R2 is a voltage divider that provides an adjustable 0-1V signal on the non-inverting input. R4 provides a bit higher maximum output voltage from OA1. Q1 and Q2 form a darlington pair. R1 is the current sense resistor.

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  • \$\begingroup\$ Can I use a MOSFET instead of the Darlington pair and go higher than 1A? I have RFP12N10L. \$\endgroup\$ – Dragos Puri Sep 7 '15 at 14:06
  • \$\begingroup\$ There are examples with MOSFETs elsewhere on SE.. You may need to add compensation to keep it stable. Reduce the sense resistor. Tip31 is good for 3A depending on voltage and heatsink. \$\endgroup\$ – Spehro Pefhany Sep 7 '15 at 15:06

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