This Digital Potentiometer Arduino Shield is based on AD5206 6 digital potentiometers. The shield includes components to give the user the possibility to experiment real applications, with two suggested inspiring examples. A cheap device that can fit in your project, not limited to audio control.

The project idea

Creating the Digital Potentiometer Arduino Shield I thought to the possible range of uses aiming to produce a sort of cheap "digital potentiometer lab" to carry out actual experiments and applications.

We can find some very basic applications of the AD5206 reviewed in many blogs and sites, including the arduino.cc website "Controlling a digital potentiometer using SPI" Unfortunately these tutorials focus on the way you can control the chip: the SPI (= Serial Peripheral Interface). Also the sample Sketches I have found on the net - limited to very few lines of code - are very simple but also almost useless.

Also the usage suggestions are very poor: you can control digitally the audio levels of some devices. But then? It's up to you. Nothing else.

The advantage of digital controls

Why we should use - in a real scenario - a digital potentiometer? As a matter of fact, we should use a digital potentiometer in every case we need a variable resistance controlled by another event. For example, one of the most common ways is changing the volume of an amplified sound depending on an external condition, e.g. the audio volume: with a sound sensor in a room we can adjust the music output level in order to compensate the room noise. Another example may be a sensor following the movement of a subject to increase the sound level of the neartest speakers. By continuing the exploration of the world of audio controls we will discover almost unlimited possibilities.

But audio is not the only case, as you can see in the video showing how this shield works.

Complete and usable

So, not only the shield circuit connects the AD5206 Digital Potentiomer device to the SPI signals of the Arduino board.

Analog testing and regulation trimmers

There are 6 trimmers connected to the 6 analog PINs on the Arduino board to be used for testing purposes or to generate an analog predefined value (e.g. as a preset level for the microcontroller). The triggers can be excluded one by one through the dip switch freeing the corresponding Analog PIN for other usages.

SPI clock LED

The SPI Clock Signal is also connected to a yellow LED: when it is blinking the communication between Arduino and the AD5206 device is working and the digital potentiometer is receiving data.

• Note that the digital potentiometer is internally latched: this means that when the circuit is powered, the device retains the last settings sent.

External VCC Ref

As the device can work at a reference VCC between 2,7 and 5,5V the jumper JP3 (Internal Pwr) uses the Arduino power supply. When unplugged, an external reference voltage can be used. In this case the external reference voltage should be connected to the pin 2 of the connector JP1.

• When connecting an external circuit, the shield circuit GND on pin 1 of the connector JP1 should be connected to the external circuit GND.

Testing and setting LEDs

Connected in parallel to each potentiometer output of the SD5206 there is a red LED for testing purposes (LED1 ... LED6). When connecting an external device, it is preferable to disable the test LEDs disconnecting the jumper JP2. The 6 digital potentiometers outputs are available on the pins 3-8 of the external connector JP1.