Rotary Encoder?

[idlefaction]

i'm not sure if such an animal exists, but i'm wanting to find a rotary encoder that has two sets of contacts and pulses one set if you turn it one way and another set if you turn it another way.

it's for hotrodding a synth i have, a Korg Poly 800.  i'm sick of pressing the + and - buttons to change parameter values and would love to add an encoder in parallel with them.  the + and - buttons are SPST momentary NO types, i'm just not sure if there is anything out there that does what i'm hoping for.

i've tried looking at datasheets on the ALPS website for their stuff but it doesn't seem to be too helpful in actually telling me how their stuff works!  has anyone used anything like this before?

thanks

[Paul Perry (Frostwave)]

No need for the "doubtful sound", I searched Google for

"rotary encoder" up down schematic

and, lots of stuff there.
I'm not a digital designer, but I know there are a few ways to do it, depending on the type of encoder, whether it is an absolute value position encoder or one that just signals change of direction.
I have some small Alps encoders if you need them 9accidentally got a stack of PCB mount ones without bushing).

[idlefaction]

hrm.  pretty much all the encoders i've been able to find info on somehow provide two signals, which are in phase mostly but when you turn it one way they go out of phase in one direction and when you turn it the other way go out of phase in the other direction.

i found a circuit on EDN to decode that into a logic 0 or 1 and a clock, so i guess if i go ahead with this idea i'd need to also run the clock and logic output into some way of 'closing' the switches.  probably a low-power relay and some logic;  clock AND logic for one output and clock AND NOT logic for the other  

ahhh this is way interesting!  and thanks for the offer paul  

[R.G.]

There are two directional encoders in every computer mouse.[/quote]

[erikfriend]

Here is a schematic that converts the offset pulses of an incremental rotary encoder into two outputs (A and B), A pulses for clockwise and B for counter-clockwise.

http://basicelectronic.blogspot.com/2006/08/rotary-encoder-converter-circuit.html

The circuit relies on a dual flip-flop chip (74HC74D).  The outputs of the encoder each drive the data input of one flip-flop, but drive the clock of the other.  ex: pulse A goes high on the data, then pulse B goes high on the clock, which locks in the high data and outputs high on that flip flop.  The other flip-flip sees clock high first while data is still low, thus locking in a low state and outputting low of the other flip-flip.  It took some head-scratching before I understood how it worked.  The end result is 2 outputs.  One has pulses when you turn clockwise, the other will only have pulses when you turn counter clockwise.  Wire those outputs to control switches (transistor? optocoupler?) and you could replace the data up/down buttons on the poly-800.

[~arph]

There are two directional encoders in every computer mouse.

Not anymore