Encoders Vs Potentiometers Dissertation research

Other Hardware General Electronics
1

Hello everyone,

I am working on a piece of audio hardware for my dissertation and would like to ask for some help please.

I want to implement a preset/recall system in to the front panel of my hardware and wondered it if would

be best to use potentiometers or encoders? I understand that with encoders they are relative so the

position of the knob would not affect things in the same way a pot would. If anyone can please give me

any advise to which they feel would work better and why I would be most appreciative. Also if you are able to list me some pros and cons of each device that would be amazing.

Many Thanks
Wayne

P.s please ask if you need any more information

2

I want to implement a preset/recall system in to the front panel of my hardware and wondered it if would

I have no idea what that means...

I understand that with encoders they are relative so the position of the knob would not affect things in the same way a pot would.

Pots are analog encoders are digital. That probably doesn't make any difference if the output of a pot is connected to an Arduino ADC input.

Pots have "mechanical memory". If you set the volume control pot on your radio to 50% and turn power off, the next time you turn on the radio the volume is still at 50%. If you want the same behavior with an encoder, you have to store the information in non-volatile memory.

The lack of mechanical memory means that [u]pointer knobs[/u] or markings on the front panel don't make sense.

Most pots rotate 270 degrees and most rotary encoders rotate more than 360 degrees and can be rotated continuously. This means you can get more (mechanical) resolution from an encoder. You can also do tricks in software such as "acceleration" where fast encoder rotation makes a bigger difference than slow rotation (higher resolution when you move it slowly for finer adjustments).

3

Why not use a Digital potientiometer ?
They have been around for years and are used everywhere you have an "up" and a "down" button for sound control.
They came around exactly because of the widespread use of microcontrollers to store and control the behaviour of all kinds of apparatus.

4

You can get absolute encoders, not just relative - there are many varieties and technologies
used.

To recall you would need some sort of motor or actuator - another reason to consider digital
potentiometers.

5

You will note that most audio equipment - car radios, TV, hi-fi and such - no longer uses mechanical potentiometers.

There are two reasons for this; one is reliability as mechanical potentiometers wear with use and become noisy and "scratchy" which is very annoying. (There is of course, substantial variation in quality of parts.)

The other is the expectation of remote control - adding a motor (servo) to control each potentiometer is unreasonably expensive.

On car radios, it is usual to have the one rotary encoder operate many functions - Volume, bass, treble, rear volume and even tuning.

In general therefore, it is more flexible and more reliable to use a rotary encoder, generally with a "push" switch function to select different actions, as the control. The ability to make multiple revolutions gives it immensely more resolution than a single turn potentiometer. The only problems to be solved are as noted above, retention of current settings over power-down, and the need - if it exists - to indicate the current setting.

Another consideration is the complexity of the equipment, for example an audio mixer. The concern about the reliability of mechanical potentiometers is multiplied by the number which are needed and the "remote" or requirement for common ("ganged") control of many becomes a concern. An elegant solution is to use only one or two encoders in combination with a touch screen which visualises the many controls, allowing access to individual or multiple controls selected by touch and then adjusted by the master rotary encoder, with the ability to create a library of pre-defined "macro" operations.

And on the implementation side of the audio controls, it becomes appropriate instead of using multiple digital potentiometers in analog circuitry, to digitise all of the inputs and perform the mixing operations digitally with DSP functions (such as equalisation) where necessary and analog conversion at the final outputs only.

6

Thank you everyone for the replies. The controls I am looking at are for the attack, release and threshold on a compressor and gate. What I want to do is be able to make presets on the final unit that the user can recall as well as save their own.

I was swayed more towards encoders due to the fact that their physical position does not matter like pots. For example on my synths the pots will jump when turned if not set to the same physical position as the last time I used the patch.

I particularly like the idea of using a single encoder for several functions as it will clear up the front panel a lot.

Can anyone tell me what the advantages and disadvantages of using incremental or absolute encoder would be please as I am still researching this and am unsure at the moment.

Thanks Again

7

You want an incremental encoder.

An absolute encoder is nothing more than a very precise, expensive digital version of a potentiometer, therefore introduces exactly the same constraints.

8

A standard rotary encoder will make a series of pulses that you interpret into the direction it is turning (or use a chip like LS7184N to out pulses and a direction line - the faster the pulses, the faster the knob is turned.
You then use those pulses to control other stuff - like tuning up the radio dial, turning down the bass level on the equalizer, increasing the radio volume, scrolling thru a menu.
The settings selected are then saved, sometimes in the device selected, sometimes in general EEPROM area (as in Arduino) to be recalled after a reset or power cycle.
Some examples:

You can have Detents, so you will physically feel a click as it rotates and a definite stop point when released . You can have a push button/switch to select a choice after you have dialed thru. You can have a high number of pulses as you rotate the knob, or a lower amount if you don't want things changing as fast (or, you slow things down in software). And of course many mounting/wiring options.

LS7183N_LS7184N.pdf (359 KB)