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Topic: How to choose a potentiometer? (Read 11804 times) previous topic - next topic

tep

Hello!
I have a simple newbie question: How to choose a potentiometer?
I already used one I had, but can I use any, for example a 5O kOhm one?
Will it react differently than a 10 kOhm one?

Thanks! ;)

AWOL

So long as all you're using them for is a voltage dividers as inputs to the A/Ds, then a 50k is as good as a 10k.
The only other thing to watch out for is whether the pot is a log (usually used for volume controls) or linear.


anachrocomputer

The value of the pot is not critical, as mentioned above.  But you should avoid very low values (less than about 1k Ohms) and very high values (more than about 50k Ohms).  Stick to using linear pots, not logarithmic ones (i.e. don't use audio volume controls).  As for the physical form of the pot, use whatever suits you application!  You can get "pre-set" pots, which are turned with a screwdriver, rotary pots that have a knob attached, or slider pots that look like faders on a mixing desk.

tep

Yes, then 50 kOhm should be ok. BTW, I just saw that the rotary one I have is 50k!
I was looking for faders, so if those are linear - what I think - it will be good :)

tep

Hm, "Audio slide pot" is written, I'm waiting for his answer!

anachrocomputer

That eBay description tells you everything except whether they are LOG or LIN pots!  But if they are intended for audio volume or level controls, they will be LOG, and therefore no good for the Arduino.

mem

50k will certainly work but the datasheet for the arduino chip recommends 20k or less. higher than 20k may slow down the conversion time - if you need to purchase pots, go with 10k or 20k.

tep

Ok, but I live in the south of France and don't see how to get faders at a good price...
Here the 50k one seem to be fast enough, I see no delay?!

mem

were talking microseconds -  you won't notice anyting unless you have a very time critical application

Have fun!

anachrocomputer

Isn't there a French equivalent of a supplier like Farnell?

tep

#11
Apr 09, 2009, 10:05 am Last Edit: Apr 09, 2009, 10:54 am by tep Reason: 1
@mem: It's quite time critical, but 1 millisecond is ok too!
@Anachrocomputer: I got the answer from the eBay seller, and those are log...
Farnell sells in France but:
- It's written that they only sell to professionals, I don't know what to think about it...
- It's quite expensive... the first one would be http://fr.farnell.com/alps/rs4511150k/potentiometre-50k/dp/698040 (but only 4 in stock, it's obsolet) and the second http://fr.farnell.com/alps/strs30102k/potentiometre-rectiligne-50k/dp/1191729 and the prices don't include VAT. So 2,45?+VAT=2,93 each! It's cheaper by Sparkfun...
But 5 pots for 13,8? (by SFE)... I must think about.

Or do you have other ideas?

Edit: Mouser's price are very good, but 20? shipping...  :o

mem

these are a little cheaper

and get 10k ones if you have a choice.  

tep

Yes thank you, they make shipping discount so it is 11,15? for 5 with shipping... that's perhaps the best solution.

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