Potentiometer min and max value

Question

I purchased several of these to drive high power LEDs on a custom project : https://www.amazon.com/gp/product/B019W4C5IE/ref=ppx_od_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

These LEDs are to be driver at around max 0.9A around 35V, I can do that easily with these boards. I'm trying to design a better way to use the system now. I'm using the current control potentiometer as a dimmer for the LEDs which works fine. My goal is to find a slider potentiometer to replace those little trimmers. The problem is that right now those trimmers aren't the perfect way to drive the led, because there is a point in adjustment where it will no longer limit the current (I can see it on the ampmeter on my test bench) and the current will just increase as the LED heats, same under a certain value the LED will stay at the minimum 0.2 amps the board specs and won't go lower.

My goal is to find a way to set endpoints on the build so that the physical minimum and maximum values of the potentiometer match the measured values of those two measured endpoints on the trimmer, I don't know if this is possible using additional resitors in series or parallel with the slider potentiometer I'm planning to use.

• Is there a way I can set the minimum and maximum value of a potentiometer with extra resistors or some other solution?

Answer 1

Well, you kind of obviously can:

^{simulate this circuit – Schematic created using CircuitLab}

If your potentiometer allows values in \$[a,b]\$, then your maximum resistance is

\begin{align} R_{\text{max}} &= \frac1{\frac1{R_{\text{series}}+b}+\frac1{R_{\text{parallel}}}} \end{align}

and likewise, your minimum resistance is

\begin{align} R_\text{min} &= \frac1{\frac1{R_\text{series}+a}+\frac1{R_\text{parallel}}} \end{align}

Solving for the different resistors is left as an exercise to the reader.

However, since the minimum value probably should be orders smaller than the maximum value, things simplify to

\begin{align} R_\text{min} &\approx R_\text{series}\\ R_\text{max} &\approx R_\text{parallel}||b \end{align}