Hello everyone,
I need to use a potentiometer and I wanted to ask you a few questions.
This may have been asked before, my apologies if that's the case.
I am currently using a linear potentiometer but I need a rotary one, like a knob that I can turn.
However, I need something that can turn indefinitely. I don't want something that goes from, say, 0 to 10 and then stops but something that keeps turning and increasing or decreasing values
I need the values to increase linearly
Also, I need this for an experiment, therefore I need something quite accurate. The one I use now has quite some noise/jittering (I'm not an engineer, forgive my terminology).
Can someone suggest me one? I've seen a few online but I'm not sure whether they will be good for what I need.
There is no such thing as a potentiometer whose value can continue increasing indefinitely. There are multiturn pots but they have a maximum value. And there are rotary encoders that can turn indefinitely but they don't have any resistance value they just provide a signal as they are moved.
As Slipstick pointed out you asking for something that is not possible. There are potentiometers that increase for up to 10 turns, but not more. There are also 'continuous turn pots. Those are basically regular potentiometer with the end stops removed. I have one commercially made removed from some equipment. It smoothly turns 360 degrees, but there are problems when you actually reach the end of the resistive material and hit the connecting rivets on the ends.
So, it is actually ok if the pot doesn't turn indefinitely.
What I need to achieve is just a higher "moving range" than the linear one.
In the experiment, participants would use the potentiometer to speed up or slow down the flashing of a stimulus on the screen.
Ultimately, there is also a limit on how much you can speed up or slow down the stimulus. At some point, it will obviously stop or move so quickly that it will basically be always showing on the screen.
Hence, it would be enough to have a pot that I can turn more than once.
Paul_KD7HB mentioned a pot that you can turn up to 10 times. Could you suggest me one?
Or, at least, some pot that you can turn a few times?
Gluce:
In the experiment, participants would use the potentiometer to speed up or slow down the flashing of a stimulus on the screen.
Use a rotary *encoder *and have it inc/decrement some variable which controls the timing. The knob can turn infinitely and the change between steps can be set as large or as small as you wish. Likewise, the endpoints can be set programmatically to whatever you want.
You stated you needed a pot, and you mentioned needing accuracy. Turns out neither requirement was right. You may well need to record flashing rates accurately, but as the rotary control is in a human feedback loop its accuracy is non-critical - stability, sufficient resolution and monotonicity are the requirements I think.
If you'd stated what you were actually doing most of this would have been clear from the outset. Some xyproblem confusion would have been avoided. Check out xyproblem.info
Thank you all for your suggestions and info.
After some considerations, I was thinking of using this: Vishay 534B1102JCB 1K 2W Multi Turn Wire-wound Potentiometer | Rapid Online
Apparently, I should be able to turn it 10 times. Also, as I understand, the fact that it is 1K means that it should be quite precise. Is that correct?
Anything I should know about this before buying?
Gluce:
Thank you all for your suggestions and info.
After some considerations, I was thinking of using this: https://www.rapidonline.com/vishay-534b1102jcb-1k-2w-multi-turn-wire-wound-potentiometer-65-1035
Apparently, I should be able to turn it 10 times. Also, as I understand, the fact that it is 1K means that it should be quite precise. Is that correct?
Anything I should know about this before buying?
Thank you all again.
Who knows what you mean by "quite precise". Look at the data sheet. Quite precise is not one of the specifications. Being wire wound means it will be stable as far as temperature is concerned.
What you seem to be looking for is a "360 degree continuous potentiometer" and like any potentiometer they have a max value so for example 0 to 359 degrees of rotation is for example 0 to 10K Ohms. So you get 0 to 10K and start again at 0. I have used them and can't remember a manufacturer. A Google of "360 degree continuous potentiometer" will get some hits including some back to this forum which I didn't read. There are also devices like this which have continuous rotation 360 degrees and on board electronics where 0 - 359 degrees = 0 to 5.0 volts. That's 13.8 mV / Degree Rotation.
Just copy and paste the link, sorry as I am still working on getting replies correct.
The resistance value 1K has nothing to do with how precise it is. If your existing linear pot is 1K then stick with that value. Otherwise 5K or 10K are probably more common values.
Linearity is probably as close as you'll get to a specification of "precise"...basically how accurately the resistance reflects the amount of rotation. It's given as +/-0.25% which is pretty accurate.
When I've needed multiturn pots in the past I've used Bourns but the specifications of the Vishay ones seem pretty much identical.