potentiometer as variable resistor - Electronic Circuits Projects Diagrams Free

justDIY · 7th December 2006, 03:41 PM

when using a pot as a variable resistor, what is the purpose of connecting the wiper to one of the resistance legs?

some schematics show the wiper tied to one leg, other show the unused leg floating.

**Nigel Goodwin** · 7th December 2006, 03:45 PM

It makes no difference if everything is OK - but if the wiper should go O/C then the resistance goes O/C - except if the wiper is connected to the end, then it goes to maximum resistance.

justDIY · 7th December 2006, 04:15 PM

aah that makes sense - thanks!

Sceadwian · 8th December 2006, 02:19 AM

Just be careful about power disipation, as it's very easy to violate a POT's power rateing using it as a resistor if you get too close to the low ohm end.

Hero999 · 8th December 2006, 03:01 PM

In my oppinion potentiometer shouldn't have just a power rating, they should have a current rating. For example 100mW might be alright if it's heating the entire track but not if it's only heating a small portion of it.

philba · 8th December 2006, 04:17 PM

just put a fixed resistor in series with the pot. Size it to the max current you want through the pot (or based on other factors in your circuit).

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7th December 2006, 03:41 PM	(permalink)
justDIY	potentiometer as variable resistor when using a pot as a variable resistor, what is the purpose of connecting the wiper to one of the resistance legs? some schematics show the wiper tied to one leg, other show the unused leg floating. __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

7th December 2006, 03:45 PM	(permalink)
Nigel Goodwin	It makes no difference if everything is OK - but if the wiper should go O/C then the resistance goes O/C - except if the wiper is connected to the end, then it goes to maximum resistance. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

7th December 2006, 04:15 PM	(permalink)
justDIY	aah that makes sense - thanks! __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

8th December 2006, 02:19 AM	(permalink)
Sceadwian	Just be careful about power disipation, as it's very easy to violate a POT's power rateing using it as a resistor if you get too close to the low ohm end. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

8th December 2006, 03:01 PM	(permalink)
Hero999	In my oppinion potentiometer shouldn't have just a power rating, they should have a current rating. For example 100mW might be alright if it's heating the entire track but not if it's only heating a small portion of it. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

8th December 2006, 04:17 PM	(permalink)
philba	just put a fixed resistor in series with the pot. Size it to the max current you want through the pot (or based on other factors in your circuit).