Buying load resistor for lab

Thread Starter

Track99

Joined Jun 30, 2022
18
Hello my friends.
Imagine that you are performing a simple electronics 101 learning experiment in the lab. You need to simulate the load.

1) What device is the best choice in the world to simulate a load?
2) Can we use a resistor as a load if the power value of the resistor is good?
3) Can we use a potentiometer to simulate loads with different resistance values ot does walmart sell another instrument that will let us set different load values? ( I dont want to buy 20 different resistors. I want to just buy 1 potentiometer and use it at different resistor values. Can u do this and is this safe?)

Thanks to my friends.
 

Wolframore

Joined Jan 21, 2019
2,564
since most of us have worked through this type of problem, there's no value to us to just give you the answer. You will not learn this by just having someone answer it. Dig deep and answer the questions and we will assist.
 

dl324

Joined Mar 30, 2015
14,897
I dont want to buy 20 different resistors. I want to just buy 1 potentiometer and use it at different resistor values. Can u do this and is this safe?
Not with your typical potentiometer that's going to be rated for less than a couple watts. You might be able to do it with a rheostat.

I thought about this once, and the solution I came up with was to use an LM317, and an external pass transistor, with appropriate heatsinking and varying the voltage across a low ohm, high-power resistor to vary the load current.
 

WBahn

Joined Mar 31, 2012
26,829
Hello my friends.
Imagine that you are performing a simple electronics 101 learning experiment in the lab. You need to simulate the load.

1) What device is the best choice in the world to simulate a load?
2) Can we use a resistor as a load if the power value of the resistor is good?
3) Can we use a potentiometer to simulate loads with different resistance values ot does walmart sell another instrument that will let us set different load values? ( I dont want to buy 20 different resistors. I want to just buy 1 potentiometer and use it at different resistor values. Can u do this and is this safe?)

Thanks to my friends.
The first question is whether the load you are trying to simulate is adequately modeled by a resistor at all. If your load has a significant reactive component to it, this may not be the case.
 

crutschow

Joined Mar 14, 2008
30,419
1) What device is the best choice in the world to simulate a load?
If you want a load to dissipate power, then you can use a power resistor.
2) Can we use a resistor as a load if the power value of the resistor is good?
If by good you mean a power rating of at least 125% of the maximum load, yes.
3) Can we use a potentiometer to simulate loads with different resistance values ot does walmart sell another instrument that will let us set different load values?
Yes, as long as the current doesn't exceed a value as determined by the P = I²R rating of the pot where R is the pot rated resistance (not the resistance setting), I is the current through the pot, a P is the power rating of the pot.

How much power must the load dissipate?
 

Wolframore

Joined Jan 21, 2019
2,564
We have one of these in the lab, it's not bad for the price. electronic load

You can use load resistors but as others have pointed out you have to calculate for heat dissipation. Most potentiometers are not designed to carry a lot of current, so you need to be aware of their power rating. look at rheostats and variacs... you can find old surplus stuff that works in a pinch. The electronic load above is very useful and versatile.
 

MrChips

Joined Oct 2, 2009
26,774
When you say “load” you need to specify resistance, voltage, current, wattage, frequency, etc.

I have a number of these power rheostats. Some are water cooled.

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WBahn

Joined Mar 31, 2012
26,829
Electric heater coils out of a clothes dryer? You can select different resistances with alligator clips.
One potential problem here is that the resistance will change with the amount of power dissipated. That's probably not desirable for most applications.
 
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