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Topic: Potenciometers with 6 pins, what to do (Read 6255 times) previous topic - next topic

swizzy555

Apr 14, 2015, 04:22 pm Last Edit: Apr 14, 2015, 04:57 pm by swizzy555
I bought a potenciometer with 6 pin but i dont know how to connect it to a servometer because all the projects ive seen only had 3 pin, how can i connect the two please

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

swizzy555



alnath

you've got actually 2 potentiometers, which values are supposed to change equally just using one knob.
if you need only one potentiometer, then use only one of them - use three pins that are in line, on the same bakelite (don't know the english word for that ;) ) support.

swizzy555


MorganS

Phenolic is the word you are looking for. That brown PCB material is called phenolic. Bakelite is black. Green PCB is fibreglass. Other colours are usually a coloured soldermask painted over the top of a fibreglass board.
"The problem is in the code you didn't post."

Grumpy_Mike

#7
Apr 14, 2015, 08:02 pm Last Edit: Apr 14, 2015, 08:02 pm by Grumpy_Mike
The potentiometers ( please note the spelling ) are known as "ganged" and are normally used for stereo amplifiers for the volume and tone control.

They have a log taper which means that they will not produce a constant change in resistance for a constant change in angle. This will probably be no good for what you want to use it for as you will find some parts of the turn nothing happens and then it gets very sensitive.

You need a linear taper pot.

alnath

right, I should have mentioned that !
and thank you MorganS ;)

swizzy555

so if i want to use it to control a servomotor it is better to use the linear tape pot. If i had used the stereo type would it affect the movement

Grumpy_Mike

Quote
so if i want to use it to control a servomotor it is better to use the linear tape pot.
Yes

Quote
If i had used the stereo type would it affect the movement
You are not reading the answers you have been given. The fact that it is stereo type or ganged has nothing to do with it. It is the taper that is the problem.
http://sound.westhost.com/pots.htm

The problem you will have is that the movement of the servo will be big for a small degree of rotation at one end of the pot, and small for the SAME degree of rotation at the other end.

A linear taper pot will have the same movement of the servo for the same degree of rotation anywhere over the range of the pot.

DVDdoug

#11
Apr 15, 2015, 04:52 pm Last Edit: Apr 15, 2015, 04:53 pm by DVDdoug
so if i want to use it to control a servomotor it is better to use the linear tape pot. If i had used the stereo type would it affect the movement
The problem isn't that it's stereo (two ganged pots that move together). 

The problem is the logarithmic taper.  Our ears are approximately logarithmic, so a volume control (a logarithmic pot) set at the half-way point is putting-out about 10% of the signal.   But, it sounds  like more than 10% to our ears.       

If you use that log pot with a servo and your servo has 270 degrees of rotation, moving the pot to the mid-point will move the servo about 27 degrees instead of 135 degrees (to the servo's mid-point).    You'll still get the full servo rotation but most of the servo's rotation will happen with the pot almost fully-rotated and the adjustment will get "touchy" where a slight movement of the pot makes big resistance change.     

MarkT

People always call it a logarithmic taper, but its really exponential since you think of the
angle as the input and the resistance as the output, not the other way round!
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Grumpy_Mike

#13
Apr 15, 2015, 07:23 pm Last Edit: Apr 15, 2015, 07:24 pm by Grumpy_Mike
People always call it a logarithmic taper,
Yes they do, but that is what the catalogs call them so that is what, when giving advice to a beginner, we must call them.  ;)

Zapro

Actually, factories cheat, as it's quite hard to manufacture a truly logarithmic resistance track in the pots:

https://www.youtube.com/watch?v=q1lbDai6ObA

I didn't know this before i saw the video. Quite an eye opener.

// Per.

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