How to connect a potentiometer

giralfino · 17th June 2010, 02:27 PM

Hi all,
I'm building a mono chip amp based on TDA7240A and want to add a potentiometer as a volume control. I have in house a 20K stereo log pot that I could use since it is of good quality. My problem is how to identify the three contact I should use (in from source, out to amp, ground), from the six that there are on the pot.
Thanks,
Ralf

firechief · 17th June 2010, 03:04 PM

Potentiometers (Beginners' Guide to Pots)
Here is all of the information you need.
Sounds like you have a dual pot. That could be handy

giralfino · 22nd June 2010, 12:41 PM

Unfortunately the article doesn't solve my problem.
I should explain better the situation: I have a pot with 6 terminals in a row, they are not marked in any way, so I can't figure what are the three terminals I have to connect (in , out, ground).
Is there a way with a simple ohm meter to find the correct ones?
Thanks,
Ralf

sregor · 22nd June 2010, 02:24 PM

Shouldn't be that hard. Turn the pot counter clockwise - volume all the way down. 2 pairs of contacts should read zero ohms to each other. The other two contacts should read 20k ohms to one of the first set of contacts. These two would be the high side. Then turn the volume all the way up - clockwise. The 20k ohms taps previously determined will read zero ohms to one of the other taps. This tap will be your wiper. The last tap would be the low side. High side = in Lowside = ground Wiper = out. Good luck with it.

firechief · 22nd June 2010, 03:49 PM

A pot with six terminals in one row is a very strange animal. I was thinking it was two rows of three terminals. in any case sregor is describing a valid technique. If all else fails, a picture Im sure would make a big difference.

Mooly · 22nd June 2010, 04:55 PM

Seen some odd ones before, five terminal ones.

RK14J12R0A01 datasheet pdf datenblatt - ALPS ELECTRIC CO.,LTD. - With Knob Type ::: ALLDATASHEET :::

giralfino · 24th June 2010, 06:24 PM

For your curiosity I attach a photo of the pot, it was used as a volume control in a Philips mini system.
I think I have found the right contacts: pins 2,3,5 from the right.
At zero volume, pins 3-5 is 0 Ohm, 2-3 and 2-5 is 20K Ohm, while at maximum volume pins 2-3 is 0 Ohm, and 2-5 and 3-5 is 20K Ohm.
Thank you all
Ralf

Mooly · 24th June 2010, 06:31 PM

Thanks for posting the picture... I'd forgotten many all in ones have motorised VC's... and I've worked on enough over the years.

Thanks.

17th June 2010, 02:27 PM	#1
giralfino diyAudio Member Join Date: Feb 2009	How to connect a potentiometer Hi all, I'm building a mono chip amp based on TDA7240A and want to add a potentiometer as a volume control. I have in house a 20K stereo log pot that I could use since it is of good quality. My problem is how to identify the three contact I should use (in from source, out to amp, ground), from the six that there are on the pot. Thanks, Ralf

22nd June 2010, 02:24 PM	#4
sregor diyAudio Member Join Date: Jan 2006 Location: massachusetts	Shouldn't be that hard. Turn the pot counter clockwise - volume all the way down. 2 pairs of contacts should read zero ohms to each other. The other two contacts should read 20k ohms to one of the first set of contacts. These two would be the high side. Then turn the volume all the way up - clockwise. The 20k ohms taps previously determined will read zero ohms to one of the other taps. This tap will be your wiper. The last tap would be the low side. High side = in Lowside = ground Wiper = out. Good luck with it. __________________ Steve

22nd June 2010, 04:55 PM	#6
Mooly diyAudio Moderator Join Date: Sep 2007	Seen some odd ones before, five terminal ones. RK14J12R0A01 datasheet pdf datenblatt - ALPS ELECTRIC CO.,LTD. - With Knob Type ::: ALLDATASHEET ::: __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

24th June 2010, 06:31 PM	#8
Mooly diyAudio Moderator Join Date: Sep 2007	Thanks for posting the picture... I'd forgotten many all in ones have motorised VC's... and I've worked on enough over the years. Thanks. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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17th June 2010, 03:04 PM	#2
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	Potentiometers (Beginners' Guide to Pots) Here is all of the information you need. Sounds like you have a dual pot. That could be handy

22nd June 2010, 12:41 PM	#3
giralfino diyAudio Member Join Date: Feb 2009	Unfortunately the article doesn't solve my problem. I should explain better the situation: I have a pot with 6 terminals in a row, they are not marked in any way, so I can't figure what are the three terminals I have to connect (in , out, ground). Is there a way with a simple ohm meter to find the correct ones? Thanks, Ralf

22nd June 2010, 03:49 PM	#5
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	A pot with six terminals in one row is a very strange animal. I was thinking it was two rows of three terminals. in any case sregor is describing a valid technique. If all else fails, a picture Im sure would make a big difference.

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