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Maybe you remember that very old (and sturdy!!!) electrical panels/machines had those big knobs that you could turn to fixed positions (steps) with a very unique clicking sound. I need to make one or get something similar so the potentiometer in my design stays on one of the 10 predefined positions.

Could you point me in the right direction? Maybe those kind of knobs have a specific name? Maybe even the pots themselves are special...

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    \$\begingroup\$ I don't know about buying one with discrete steps; this guy made one, maybe you'll draw some inspiration from it: instructables.com/id/… \$\endgroup\$ – Nick Williams Dec 28 '13 at 20:14
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    \$\begingroup\$ I'm not 100% certain what you're looking for, but it sounds like a rotary switch. \$\endgroup\$ – Matt Young Dec 28 '13 at 20:17
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    \$\begingroup\$ Use a rotary switch, and add resistors between the positions as necessary. Rotary switches are available with up to 24 positions \$\endgroup\$ – Peter Bennett Dec 28 '13 at 20:20
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    \$\begingroup\$ In radio studios, these used to be known as "stud faders" - a little smoother than most rotary switches, but that is what they were. \$\endgroup\$ – Brian Drummond Dec 28 '13 at 20:31
  • \$\begingroup\$ My audio amp isn't that old and it has a volume pot like that. I bet they are still available. Maybe not el-cheapo variant, but the quality audio sources. I think my amp's pot has maybe 100 steps or more over 300 degrees. \$\endgroup\$ – jippie Dec 28 '13 at 21:02
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To search for the described part, use the keywords potentiometer with detents.

The specifics mentioned would suggest a potentiometer with 10 detents, such as this one on Amazon, or another on Jameco.

Pot with detents

The detents can be low torque (a gentle click at each transition) or high torque (a firm click). The common / inexpensive ones are low-torque, but they seem to survive longer than a few high-torque pots with detents I have used.

More expensive such potentiometers allow individual mechanically adjustable detent torque, even to the extent of mixing high and low torque detents within a single pot (example).

Adjustable detent potentiometer

At the high end of the spectrum, some manufacturers offer programmable detent torque: Internally these are essentially like stepper motors integrated with the potentiometer shaft, with the externally controlled coil current determining the holding torque at each detent position. I haven't seen this type available in retail, only through OEM sales by quotation.

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  • \$\begingroup\$ Thank you, it seems this is just the thing I needed! Too bad they are quite a bit more expensive. \$\endgroup\$ – Sebastian Rivas Jan 2 '14 at 23:04
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Maybe this will help (10 positions, 4 resistors). Decade Switch

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If you want it to actually increment the resistance in steps, you don't use a pot at all. Instead, you use a rotary switch and resistors. I am writing this on my iPod so I don't have access to the schematic editor, but I will edit as soon as possible.

EDIT: Here is a diagram (I had to improvise, no symbol for a rotary switch):

schematic

simulate this circuit – Schematic created using CircuitLab

If, on the other hand, you just want the physical clicking effect, you can get special knobs. These knobs have a little ratchet-type sweeper in them that means it can only stop at certain points. They are a little hard to find these days, but you could probably make one yourself with a bit of effort. You would want to attach a sweeper to the shaft and have that sweeper click past little posts or notches. If you have some experience making small mechanical parts, or could get the help of someone who does, that would help a lot.

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  • \$\begingroup\$ Rotary switches sound like a good option, but what happens in between clicks? Does the pin float or is it always between lines? \$\endgroup\$ – Sebastian Rivas Dec 30 '13 at 0:45
  • \$\begingroup\$ @SebastianRivas Most rotary switches are "break before make" Therefore, in between notches there would be a short period where there is no contact at all. If this is a problem I believe you can buy special rotary switches where this period of non-contact is only nanoseconds long but they are more expensive. \$\endgroup\$ – felixphew Jan 1 '14 at 21:18
  • \$\begingroup\$ @Sebastian : I solved that in software ,checking if an output is stable during a couple of milliseconds before acquiring the new value. \$\endgroup\$ – lode Feb 14 '19 at 22:53

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