DIY stepped pots w/rotary switches & resistors

[djmiggymigz]

Looking for some help understanding the theory behind this before I spend the money to buy the parts! Looking to replace the center indent pots on an eq I’m building with stepped and calculated switches. My plan is to use 1x12 non-shorting lorlin switches with resistors (calculated) soldered to the pins of the switch. So in theory, the restore should be wired in parallel to each other. Right? Meaning (and this is where I get iffy) that I can solder one leg of the resistors to the pins, and then simply connect all the free resistor legs together right? I’m including a little sketch of the way this works in my head. I only added resistors to pins 1 & 7-12 bcuz I can’t draw with depth lol. But the same resistor pattern would exist on all the pins. I might be missing the center post in the drawing?

One of my main questions, is after adding resistors to the switch, what switch pins correspond to the typical 3 pins of a normal pot? The build I’m working on send pin 1 and then pins 2&3 (connected) to the pcb’s. In the switch idea would those three pins correspond to pins 1, 12, and maybe the center ? How many center posts do I need?

(P.s. total noob here learning a lot. Please have patience if what I’ve said is fully wrong lol) also, I did a search and didn’t see a post dedicated to this hence the new post. Just saying that so nobody comes at me for not looking first

 

[ruffrecords]

What you have described is a variable resistor (a two terminal device) rather than a potentiometer ( a three terminal device)

To make a potentiometer you need to connect a resistor between pin 1 and pin 2, and another between pin 2 and pin 3, and another between pin3 and pin 4 and so on up to pin 12. Pin 1 is then the bottom of the potentiometer, pin 12 is the top and the wiper of the switch is the wiper of the potentiometer.

Cheers

Ian

 

[Bobby Baird]

I think he's trying to make a stepped switch for the nite 3d eq. In that case have you seen this? Rename file extension .xls

 

[djmiggymigz]

What you have described is a variable resistor (a two terminal device) rather than a potentiometer ( a three terminal device)

To make a potentiometer you need to connect a resistor between pin 1 and pin 2, and another between pin 2 and pin 3, and another between pin3 and pin 4 and so on up to pin 12. Pin 1 is then the bottom of the potentiometer, pin 12 is the top and the wiper of the switch is the wiper of the potentiometer.

Cheers

Ian

Ahhh okay so maybe it should look something more like this then? P.snif an12 position switch has 1 wiper (a) that corresponds to all 12 positions. If it has 2 (a & c) a corresponds to 1-6 and c 7-12. Is that correct?

 

[djmiggymigz]

I think he's trying to make a stepped switch for the nite 3d eq. In that case have you seen this? Rename file extension .xls

Precisely! Yes I have those docs and feel relatively good about the resistor values for the steps. Just looking for some clarification on actually putting the switches together/to use here!

 

[Bobby Baird]

Pot pins facing the shaft from left to right is 1,2,3. From the back of the pot left to right is 3,2,1.

 

[djmiggymigz]

Pot pins facing the shaft from left to right is 1,2,3. From the back of the pot left to right is 3,2,1.

Okay word thank you for clarifying that for me. With pin 2 being the wiper?

 

[Bobby Baird]

The pots on that eq are dual gang correct?

 

[Bobby Baird]

Pin 2 wiper correct

 

[djmiggymigz]

No they’re single gang I believe, they only have one set of pins.

 

[Bobby Baird]

In that case you should need single pole switch. The 1 pin in the middle of a Lorlin.

 

[Bobby Baird]

I have boards for this project too. Just never got around to it. Gasing for 2 pultecs. Plus designing board for the MEQ-5.

 

[djmiggymigz]

In that case you should need single pole switch. The 1 pin in the middle of a Lorlin.

Okay cool that’s a relief! I found on CAPI’s website that they sell a pcb to make a stepped Grayhill into a pot. Howeverrrrr the Grayhill are at the cheapest $17 per switch. I think I’m gonna go full diy and get lorlins with ressistors straight on the pins.

So pot wiper = lorlin wiper. Pot pin 1 = lorlin pin 1. And then pin 3 = lorlin pin 12?

1 -> 1, wiper -> wiper, 3 -> 12

 

[djmiggymigz]

I have boards for this project too. Just never got around to it. Gasing for 2 pultecs. Plus designing board for the MEQ-5.

Are you doing variable or stepped for the pultecs??

 

[djmiggymigz]

P.s if you want to sell those pcb’s I just mayhaps be interested!

 

[Bobby Baird]

Variable I'm not to fussy about a little boost here are there. That just widens the stereo field.

 

[djmiggymigz]

Variable I'm not to fussy about a little boost here are there. That just widens the stereo field.

Sweet, that seems like the move for pultecs. I want to use this eq for mastering/stereo buss applications so as much of a pain the stepped pots seem to be I think it’ll be worth it. Plus, this project has been SUCH a learning experience for me, I may as well take the extra step, learn what I can from it and be happy with clicky knobs lol

 

[Bobby Baird]

Did you see this schem?

 

[Bobby Baird]

I would just get the switch and resistors and experiment. Can't be to hard to figure out a solution.

 

[djmiggymigz]

Yes I did see that thanks for bumping it into my sight again tho, I think I lost that in the original thread.