Increasing the travel of a potentiometer

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SteveMD
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Increasing the travel of a potentiometer

Post by SteveMD » Wed Sep 18, 2013 11:25 am

Is this even possible?

I am adding a potentiometer to the motor of a tape player to slow it down - but even with only a 1k pot not even a quarter of the travel is used. I've tried a few different things but have yet been unable to broaden the range.

Ideally of course the pot would go its full turn. Any advice?

MKULTRA
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Post by MKULTRA » Wed Sep 18, 2013 12:59 pm

Are you using a voltage regulating circuit with said pot?

SteveMD
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Post by SteveMD » Wed Sep 18, 2013 1:19 pm

I was planning on just putting a pot between the power supply and motor, I don't have much knowledge on the matter obviously.

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xdugef
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Post by xdugef » Wed Sep 18, 2013 1:31 pm

SteveMD wrote:I was planning on just putting a pot between the power supply and motor, I don't have much knowledge on the matter obviously.
1k might be too large of a value. Also make sure you are using a linear pot instead of exponential otherwise the values increase too soon towards one end of the scale.
Last edited by xdugef on Wed Sep 18, 2013 2:16 pm, edited 1 time in total.

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crochambeau
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Post by crochambeau » Wed Sep 18, 2013 1:41 pm

Caveman method:

Stop turning the pot once you have reached the low end of usefulness, remove it and measure resistance that was in circuit. You now know the size of pot you need for the job. I agree with Xdugef in going linear.

Yes, my caveman method requires a multimeter.
MKULTRA wrote:Are you using a voltage regulating circuit with said pot?
This would be the preferred method. Loading down a pot in a current branch is probably going to result in short pot life. Not saying people don't do it, just saying it's not a hundred year design.
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fire
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Post by fire » Wed Sep 18, 2013 2:49 pm

a real caveman would throw in a low value resistor in parallel, ???
[17,963] days since last fuck given

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crochambeau
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Post by crochambeau » Wed Sep 18, 2013 3:23 pm

fire wrote:a real caveman would throw in a low value resistor in parallel, ???
A real caveman would hit the fucking device with a rock.

..and possibly try to fuck it.


.....and then move on.

But yeah, at the expense of a linear taper, Macgyvering in a resistor in parallel would be a simple solution.

Pot is still going to see current.
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SteveMD
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Post by SteveMD » Wed Sep 18, 2013 3:28 pm

Thanks for the suggestions, I'll check out the value needed with a multimeter as Curtis suggests and see where to go from there.

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Post by SteveMD » Wed Sep 18, 2013 3:44 pm

I feel very stupid - I didn't even think potentiometers were made in smaller values, turns out I need 100 ohms. Thanks again Curtis.

With a supply of 9 volts what would be the best way to set this up without destroying the pot?

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Post by MKULTRA » Thu Sep 19, 2013 2:27 am

If you can solder, you can build this.
Cheap, easy and a damned sight more versatile.
Image

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crochambeau
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Post by crochambeau » Thu Sep 19, 2013 4:57 am

SteveMD wrote:what would be the best way to set this up without destroying the pot?
MKULTRA wrote:If you can solder, you can build this.
Cheap, easy and a damned sight more versatile.
Image
LM317 should be easy to source, and is a fine part number for that diagram (swap 3 & 1).
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SteveMD
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Post by SteveMD » Thu Sep 19, 2013 12:58 pm

Thanks again everyone!

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xdugef
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Post by xdugef » Mon Feb 20, 2017 7:27 am

MKULTRA wrote:Are you using a voltage regulating circuit with said pot?

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xdugef
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Post by xdugef » Mon Feb 20, 2017 7:28 am

MKULTRA wrote:If you can solder, you can build this.
Cheap, easy and a damned sight more versatile.
Image

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timdrage
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Post by timdrage » Mon Feb 20, 2017 7:33 am

I've found cheap pre-built PWM motor speed controllers on ebay for this kind of thing, they even have screw terminals so all you need to do is clip the motor wires and connect them in series with it

made a good uber-slow wobbly walkman so far

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