Using bipolar digital potentiometers with Arduino

Other Hardware Audio
1

I am looking for a good book on using bipolar digital potentiometers with Arduino. I don't want any books that have samples of digital potentiometers turning LEDs off and on. I have seen too many of those! I am only interested in examples of bipolar operation. Bipolar operation as in AC audio. All of the audio books I have seen don't have examples of bipolar AC audio operation.

2

Do you want 0 and infinity OR 0 to max and able to get everything in-between ?

3

LarryD, I am thinking in terms of voltage, a sine wave voltage in a set range. I want to feed in a sine wave voltage of 0 to 100 mili-volts to the bipolar digital potentiometer, and be able to output any value in that range. A potentiometer is nothing more than a voltage divider, so I am dividing the input range of 0 to 100 mili-volts. If the bipolar digital potentiometer can't output that range of voltage, I can feed the output of the bipolar digital potentiometer to something that will handle that voltage. All the books I have found don't show examples of bipolar/AC operation of digital pots. Plus all the examples of digital pots in books shows them turning on LEDs---and digital pots are not designed to handle the current of LEDs. So the books I have read have screwy examples!

4

Your question was not answered last year?

5

xfpd, thanks for your post. Yes, that particular question was answered last year. This new question is a totally different question. Last year's question involved operation of a single polarity digital pot arranged to handle an AC audio signal. Please note that my current post involves asking for samples of using potentiometers factory designed for bipolar operation. Bipolar meaning dual polarity, as the post from last year involved single polarity. I am aware that single polarity potentiometers can be arranged to handle AC signals. But---I am not interested in pots manufactured for single polarity operation, just examples with pots factory designed for bipolar-AC operation. Single polarity being a plus voltage with a ground, bipolarity being a plus voltage, minus voltage, with a ground.

6

Hi @KeithHilton,

do you have a link to such a potentiometer?

ec2021

7

I was curious:

https://www.analog.com/media/en/technical-documentation/data-sheets/DS1267B.pdf

image
image1438×1470 315 KB

8

Thanks @DaveX,

would you consider this a "bipolar potentiometer"?

bipolarity being a plus voltage, minus voltage, with a ground.

If I understand @KeithHilton correctly it should look something like this:

image

???

P.S.: Regardless of that, the datasheet you linked points to an interesting device!! Thanks! Especially the neat description of how to control it by serial input ... Just found a link into the very past :wink: https://forum.arduino.cc/t/digital-pot/10032; however I believe the code in that threat will not work as ShiftOut transmits always 8 Bit and this chip requires 17 Bit ... It needs at least the Stack Bit to be transferred separately I guess...

ec2021

9

ec2021 Analog Devices is a company that makes many bipolar pots. Visit their website for a list of the pots. Below is what I copied from their website.

Do digital potentiometers handle bipolar and AC operations?

Yes, we have digital potentiometers with dual ±2.5V, ±5V, or ±15V supplies that can handle bipolar or AC operation. You can still achieve AC operation with a single DC supply if you raise the DC offset. Terminals A, B, and W have no polarity constraints with respect to each other.

10

Ok, than the datasheet linked by @DaveX is showing one of those digital potentiometers!

ec2021

11

ec2021 Here is a link that will really help you understand. I think the term most used in the industry is dual operation, instead of bipolar. This link gives you a chart of all of Analog Devices volatile and nonvolatile digital pots.
https://www.analog.com/media/en/news-marketing-collateral/product-selection-guide/choosing_the_correct_digipot.pdf

12

Now getting back on subject. I am wanting to see examples of AC audio operation using dual supply digital potentiometers with Arduino. Actual programing examples. Please no samples of digital pots turning LEDs off and on. Thanks!

13

Thanks for clarification which helped me to understand your objective!
Unfortunately I have not encountered any application of this kind.

But there are many people around in this forum ...

Good luck!
ec2021

14

I don't think the DS1267 gives you two taps. I imagine this would work like most other digital pots, but the lower end of the pot could be held below zero.

If you don't have a library for the writing, you may need to roll your own.

(Here's a hacked up version of the old copy below)

void shiftOutNBits(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t bits, int32_t val) {
  {
    uint8_t i;

    for (i = 0; i < bits; i++)  {
      if (bitOrder == LSBFIRST)
        digitalWrite(dataPin, !!(val & (1 << i)));
      else
        digitalWrite(dataPin, !!(val & (1 << ((bits - 1) - i))));

      digitalWrite(clockPin, HIGH);
      delay(250);
      digitalWrite(clockPin, LOW);
      delay(250);
    }
    digitalWrite(dataPin, LOW);
  }
}
15

Thanks, it is (at the moment) just of academic interest for me :wink: Once I have an application I will surely come back to this!

But again thanks for taking care!
ec2021

16

You may probably have a look at this comprehensive document titled

DUAL CHANNEL MATRIX SWITCH AUDIO RECEIVER
BY
AUSTIN FOX
SENIOR PROJECT
ELECTRICAL ENGINEERING DEPARTMENT
CALIFORNIA POLYTECHNIC STATE UNIVERSITY
SAN LUIS OBISPO
2015

https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1308&context=eesp

Abstract:

The Dual Channel Matrix Switch Audio Receiver controls 2 separate audio output channels. Each channel plays any of the system's 3 inputs. This controller enables a user to play two separate audio signals through two separate speaker channels. The system design allows audio input from 2 RCA sources or 1 RCA source and a phono source. The system outputs an audio signal for each output simultaneously at up to 36W on each channel for an 8Ω load. The device allows a user to control the audio input and the volume of each output channel. An Arduino Uno R3 microcontroller interfaced with front rotary potentiometers and a display creates this capability. The device operates using standard 120V, 60Hz AC power and outputs audio signals ranging from 20Hz to 20kHz.

The closest I found to your quite strict requirements ...

ec2021

17

Let me narrow down what I am looking for but have yet to find. Analog Devices make both single polarity and dual polarity digital potentiometers. The only examples I can find at analog devices, Arduino files, books on Arduino, or searching the internet---is only single polarity hook up examples of digital potentiometers. If you don't understand what I am talking about, single polarity is a + voltage with a ground--2 wire hookup. Dual polarity is + voltage, - voltage with a ground---meaning 3 wire hookup to the digital pot, not two wires. Very, very simple question of what I am looking for. I am looking for an example of a 3 wire hookup to a digital pot. I guess it is assumed you can hook up either way, like you do with op amps. Two wires around the DC voltage, or 3 wires with plus, minus, and ground. I would like to see just one example of a simple audio hookup of a digital potentiometer with 3 wire wires. All of the examples everywhere are 2 wire hookup. Can someone find me a 3 wire hookup of a digital potentiometer?