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Topic: resistance in potentiometer (Read 694 times) previous topic - next topic

hilukasz

I have two potentiometers one says A47-10K-s (assuming this is a 10k max potentiometer) and one that says A250K (assuming this is 0min - 250k max) I want to hook it up to do some tests, but not sure which is ideal for using. can either of these work? all I want to do is have arduino pick up a reading from it into a PWM input so I can affect some things in processing. any resources or link I can read up on would be greatly appreciated.
for(i = 0, i < 820480075, i++){ Design(); Code(); delay(1000); } // hellowoo.com

jackrae

Would surmise the 10k as the better since the 250k (high impedance) linearity may be influenced by the input impedance of the arduino.
However, either will work OK, just that 10k would be the better choice.

kf2qd

No Arduino input is PWM. You want to look at Analog Inputs as PWM is outputs...

dc42

Either will work adequately for feeding an Arduino analog input. What's more important is whether they are linear or log-law pots. Linear is better for this application.
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cr0sh

I have two potentiometers one says A47-10K-s (assuming this is a 10k max potentiometer) and one that says A250K (assuming this is 0min - 250k max)


Instead of assuming, why don't you check them with your multimeter, first? If you don't have a multimeter, you -NEED- to get one, and get familiar with using it.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

hilukasz

#5
Mar 31, 2012, 02:40 pm Last Edit: Mar 31, 2012, 02:43 pm by hilukasz Reason: 1

I have two potentiometers one says A47-10K-s (assuming this is a 10k max potentiometer) and one that says A250K (assuming this is 0min - 250k max)


Instead of assuming, why don't you check them with your multimeter, first? If you don't have a multimeter, you -NEED- to get one, and get familiar with using it.



I do have one. I just looked up how to do it and it and that is correct they are 10k and 250k. sorry, super new to electronics, just started this week, but I'm slowly learning. you have any suggestions for learning? I picked up a book that mentions some basics, but its more for openFrameworks/processing than electronics.
for(i = 0, i < 820480075, i++){ Design(); Code(); delay(1000); } // hellowoo.com

hilukasz


Either will work adequately for feeding an Arduino analog input. What's more important is whether they are linear or log-law pots. Linear is better for this application.


how do you tell if something is linear, can you test for this? I don't have any packaging for them anymore :/
for(i = 0, i < 820480075, i++){ Design(); Code(); delay(1000); } // hellowoo.com

pluggy

#7
Mar 31, 2012, 03:01 pm Last Edit: Mar 31, 2012, 03:06 pm by pluggy Reason: 1
Hook one side of the pot to 5V, the other to ground, and connect you multimeter on voltage setting across the centre wiper pin and ground.  Turn the rotor on the pot whilst you monitor the voltage, one end it will be 0 (or close to it) ant the other end it will be 5V (or close to it).  A linear should read close to 2.5 volts at the centre position and give a smooth transition from one to the other as you turn the knob.  A logarithmic will have 'most of it' at one end of the rotation and 2.5 volts will be close to one end of the scale.  Most pots are linear.......

Jumper leads with croc clips at either end make life a lot easier when you're doing this.  ;)
http://pluggy.is-a-geek.com/index.html

jfhaugh


Hook one side of the pot to 5V, the other to ground, and connect you multimeter on voltage setting across the centre wiper pin and ground.  Turn the rotor on the pot whilst you monitor the voltage, one end it will be 0 (or close to it) ant the other end it will be 5V (or close to it).  A linear should read close to 2.5 volts at the centre position and give a smooth transition from one to the other as you turn the knob.  A logarithmic will have 'most of it' at one end of the rotation and 2.5 volts will be close to one end of the scale.  Most pots are linear.......

Jumper leads with croc clips at either end make life a lot easier when you're doing this.  ;)


He doesn't need a power supply -- he can just measure the resistance directly.

And don't assume most pots are linear -- there are plenty of applications where log-pots are more common than linear.  Like, audio ...

cr0sh

#9
Apr 01, 2012, 02:26 am Last Edit: Apr 01, 2012, 02:28 am by cr0sh Reason: 1

you have any suggestions for learning? I picked up a book that mentions some basics, but its more for openFrameworks/processing than electronics.


If you are serious about learning electronics, then two books you should look into are:

Grob's Basic Electronics - http://highered.mcgraw-hill.com/sites/0072988215/information_center_view0/
The Art of Electronics (Paul Horowitz, et al) - http://en.wikipedia.org/wiki/The_Art_of_Electronics

You might also check out the ARRL Handbook (more focused on radio electronics, but still a great read):

http://www.arrl.org/shop/ARRL-Handbook-2012-Hardcover-Edition/

Also, pick up copies of all of the "Engineer's Mini Notebooks" by Forrest M. Mims III:

http://www.forrestmims.com/engineers_mini_notebook.html

Finally - on another thread around here someone mentioned that MIT had some kind of online free course for learning electronics; I don't know much about it, but it or similar courses might be worth checking out.

Update: Ah, here's the thread: http://arduino.cc/forum/index.php/topic,91902.0.html
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

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