How can i connect two different pots parallel like a normal pot?

Question

I am trying to make an adjustable power supply with XL4016 module and 24 volt 6,5A SMPS.

I can adjust volt with two pot (fine-course) because it needs two pins. But I couldn't think how to design a coarse / fine replacement for the current pot because it needs three pins for pot. I need middle pot pin too.

How can I connect two pots in place of a normal pot. The module wants to 10k pots.

Answer 1

Voltage adjust

The schematic shows that. R9 is a 3-terminal pot with the wiper connected to one end. This makes it a variable resistor.

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. Voltage coarse and fine.

If you want the fine adjustment control then add a 1k pot in series with R9 and with the wiper wired in the same configuration. The 10K part will then give you coarse control and the 1k pot will give you fine control.

Current adjust

^{simulate this circuit}

Figure 2. Current coarse and fine.

Note that this adds an extra 1k into the R2 - R3 potential divider but if R2 is a 1% type it's resistance tolerance is ±2.2 kΩ.

Answer 2

Put 1k pot in series with 10k pot... close enough This gives full range but not the foldback at CV cutoff when I drops <5%CC for Lithium but ok for 14.2 Lead acid

If numbered 123 the wiper going CW moves from 1 to 3 so if you to increase Vfb resistance short 12 both to increase Vout. Then R increases CW. Then a short goes to Vref =Vmin=1,5V ?

If you just want 12 to 15 why fine just use fixed 9k+ 1k pot or whatever fixed nom. you want

Answer 3

You can get pots with two tracks:

Then you can put two-terminal resistors for fine adjust at each end of the coarse pot.

^{simulate this circuit – Schematic created using CircuitLab}

But seeing as the 10K pot has much larger resistance (220K) in series at the top you could just put the fine adjust at the bottom of the 10K. there'd be a 5% difference in the fine adjust scale from top to bottom of the 10K but few people will even notice that.