Variable load with stepless current draw

[manishanand14]

Hello Everyone!

I want to make a continuously variable load[resistive] which should draw current in the range 100mA-2A.

Voltage across the load 3-12V.

 

[barry]

This means you need a 25 watt load. (12V @ 2A). A 25 watt, 125 ohm rheostat that would do the job.

Are there more requirements?

 

[manishanand14]

It may be difficult for me to get that kind of rheostat in the market.

 

[barry]

I'm not sure what you've got in India, but there's this for example:

https://www.digikey.com/scripts/dksearch/dksus.dll

These are pretty common parts.

 

[manishanand14]

Instead can I not use a suitable rating transistor in active mode.

The base current will decide the collector current which will flow through a resistive load.(Say a wire wound resistor of suitable wattage).

 

[FvM]

This means you need a 25 watt load. (12V @ 2A). A 25 watt, 125 ohm rheostat that would do the job.

The unpleasant point is to require both 120 ohm and 2 A, which refers to a 480 W rheostat, unfortunately.

Instead can I not use a suitable rating transistor in active mode.

Yes, the power rating (heatsink size) has to be selected according to the intended V and A combination.