Rotary encoder instead of buttons

robmil

Member
2004-06-11 3:55 pm
London
Hi

I have a signal switching circuit which is based solely on momentary push button and relay activation. I would like to convert part of this (volume up and down) to a rotary type. I'm not too up with rotary encoders etc. Is this a simple exercise converting up/down buttons to rotary encoder?

thanks

Rob
 
robmil said:
Hi

I have a signal switching circuit which is based solely on momentary push button and relay activation. I would like to convert part of this (volume up and down) to a rotary type. I'm not too up with rotary encoders etc. Is this a simple exercise converting up/down buttons to rotary encoder?

thanks

Rob

Hmmnn Simple is such a subjective term,

Rotary encoders must be decoded in order to make them work.

Try doing a search on gray code (a common type of encoder) to get an explanation of how it works.

You really need a processor to convert the movement of the rotary encoder to volume up and down commands. You could use a PIC or AVR controller, but this is going to take some programmming.

Maxim make a digital volume pot the MAX5440 which can take the signal direct from a rotary encoder however it only comes in a surface mount package. I have played with trying to get it to work but failed. I got fed up eventually. I have bought a pic programmer and eventually will get round to learning JAL properly in order to get the same result.

Alternatively there are a couple of people here who have programmed chips to do this. You could look through threads and ask nicely for some code. You would still need a programmer of some sort.

I an determined that eventually I will get one to work. But I dont see it as a venture that i will be able to complete in the short term.

Hope my experiance isn't too much of a downer on your idea. Rotary encoders are way cool. Digital pots have some big advantages over stereo wipers in terms of size and tracking between channels.

Push buttons are a bit easier. Maxim make a chip called the DS1802 which can be ordered in DIP and is easy to kmnock up into a design. It is limited by the voltage of your line in. Pedja Rogic has details on using this chip on his web site.
 

robmil

Member
2004-06-11 3:55 pm
London
Thanks for all the help. I think I may go for the pulse switch. I've attached a PDF of the control ciruit. It's only the volume I want on a rotary. The I/O drives a series of relays through several 4094s and 2 x ULN2003s. The preamp has a resistor ladder on it.

R
 

Attachments

  • preamp control model (1).pdf
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Well, rotary encoders use gray code (ie a certain angle corresponds to a certain code), but you could use another type which has no reference (ie you can turn it several times) and just provide a direction+pulse signal :

Sample on rising edge of "pulse" signal :
if "direction" = 1 => it was turned clockwise
if "direction" = 0 => it was turned in the other direction

It is very easy to use with a controller.
However it has no memory (ie. you can-t put 0-10 marks on the dial since there is no "0"). But I like the feeling those provide, like the iPod wheel, sort of.

OOps, I see this has been mentioned.

I will use one of those in my next project :

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1114163;keywords=25L