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newbie potentiometer question

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doctorzylo

New Member
Hi, I'm new to the forum, & electronics, & have a question about potentiometers. I'm trying to find a pot(500K) that will go from 0-10 in 1/2 or 1/3 of the normal rotation. Aside from using gears, can this be achieved
electronically? or is such a pot available? Thanks
 

EN0

Member
So you mean it has 10 settings? You want to need to turn it half as much?

You could always use a 1Meg pot and then stop it from turning after 500KOhms.

No, not "10 settings." I mean ten revolutions of turning. So the cylinder used to turn the wiper on the pot will require ten turns for it to stop at the maximum point and also the opposite point.
 

EN0

Member
doctorzylo,

They do have digital pots or analog pots, you can choose your preference. The analog pots are the ones with the cylinder wiper that you mechanically turn. The digital pots have two pushbutton switches, one to increase the resistance of the pot, and the other to lower it. Many sterio systems have this technique for volume control. Why don't you look on a distributors website such as Digi-Key or Allied Electronics and search for something like that.
 

doctorzylo

New Member
currently the sweep from 'no volume' to 'full volume' is about 270 degrees of rotation. can I go from 'no volume' to 'full volume' in less distance?
 

EN0

Member
currently the sweep from 'no volume' to 'full volume' is about 270 degrees of rotation. can I go from 'no volume' to 'full volume' in less distance?

Yes, they have pots that will provide less turns of rotation for a certain resistance. Both digital and analog.
 

kpatz

New Member
So you mean it has 10 settings? You want to need to turn it half as much?

You could always use a 1Meg pot and then stop it from turning after 500KOhms.
That will work fine for linear taper pots, but not for audio/log taper pots which are pretty much maxed out at the 10 or 11 o'clock position.

That said, if your amp has a linear pot in it now, replace it with an audio one and then your useful range will be from minimum to about the 11 o'clock position, any higher won't make much of a difference. Or just put in a linear pot and use just the last 1/3rd of its travel. The drawback of this is you won't be able to turn the volume down to zero without turning the pot all the way.
 
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Dean Huster

Well-Known Member
"Precision" or 10-turn pots are wire-wound pots that were frequently found of test and measurement equipment of the 1960s and 1970s, commonly found as the "delay time multiplier" on a delayed-sweep oscilloscope. These pots had so-so overall resistance tolerance but were VERY linear in their rotation, i.e., each turn provided the same accurate resistance change. There were also 5-turn pots available. These devices are getting hard to find as solid state circuits have made them all but obsolete.

Popular manufacturers of these were Helipot and Bourns.
 

doctorzylo

New Member
Dean, thanks for your reply. What I'm actually trying to get is a pot that goes from 'no volume' to 'full volume' in 1/3 of one rotation. Is it possible to add a resistor in line with the pot to increase the overall resistance & change the effective travel of the wiper? thanks
 

EN0

Member
Dean, thanks for your reply. What I'm actually trying to get is a pot that goes from 'no volume' to 'full volume' in 1/3 of one rotation. Is it possible to add a resistor in line with the pot to increase the overall resistance & change the effective travel of the wiper? thanks

Yes, there is a way. First you should know how resistors add in series and also in parallel, then you can go from there. For series resistors, you just add them up one by one. So for example, If I had three 100Ω resistors all in series, you would get 300Ω. As for parallel, if you add three 100Ω resistors in parallel you get about 33Ω (1/R1 + 1/R2...so on....then take the reciprocal of that).

So think about it, if we have a 50k pot and we put a 50k resistor in parallel with the two main resistor ternimals (not the wiper) we can obtain a 25k pot. Or, if we add a resistor to one of the terminals (again, not the wiper; but either ternimal besides), we'll get whatever the resistance we have the sum of the pot to that of the series resistor we added. Let me know if this makes sense, you might need a visual aid.
 

doctorzylo

New Member
So, if I had a 500k pot & wanted a 1meg pot, as Mike suggested, I would add 500k of resistance to one of the legs? A visual aid would help.
 

ericgibbs

Well-Known Member
Most Helpful Member
So, if I had a 500k pot & wanted a 1meg pot, as Mike suggested, I would add 500k of resistance to one of the legs? A visual aid would help.

hi,
One problem would be if its used as a volume control pot when adding a series 500K will be you cannot turn to min or max volume, depending which end you add the 500k.

On the present setup is the centre connector tag of the pot wired directly to another tag on the pot or is a separate wire attached.?
 

BL4CKB4NN3R

New Member
Just to clear things up (sorry if this thread is a bit old) the "1-10" is the standard numbers on a guitar adjustment knob. they don't mean anything technical, just a reference to where you are on the pot.

He would like to make it so you would only have to turn it to "5" to reach the output level of "10"
 
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