rotary encoder - simple decoder

Thread Starter


Joined Jul 13, 2019

I want to use a rotary encoder to act as a 'double switch' like this: when I rotate to right, every step that the encoder does, should act as a short contact between B1-B2 and the same when rotated to left between (A1-A2). The voltage between A1-A2 and B1-B2 should be 0, I only need a simple contact.
How can I build a very simple decoder for this situation? without programming if possible.
I did some research and I found a lot of schematics using CD4013BE and similar IC's, but I wasn't able to find exactly what I need.

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Joined Jul 18, 2013
You could decode a coarse count incremental quadrature encoder and use the A & A/ for one side and the B & B/ for the other, some logic would be involved.


Joined Aug 27, 2009
I never heard about this kind of switches, I have to check them out
I've used them in some applications instead of quadrature encoder types when I needed a very firm feel to each input change increment. You might need to debounce the contacts if the pulse reading device is sensitive to that sort of thing.

Thread Starter


Joined Jul 13, 2019
At the moment I'm not able to find this item in our biggest national stores, but I have to dig more.
But just in case, can you recommend me a simple quadrature encoder circuit?


Joined Sep 24, 2015
Those sorts of switches are simply a series of switches that can select a common point to any of (in the case of the example six position switch) any of the pin-outs. Let's call A "common". A six position switch will make no contact between any of the points. Rotate it one position and A is not connected to pin 1. Rotate it one more position and A is not connected to pin 2 - and so on.

A rotary encoder switch is just two switches that open and close a single set of contacts for each portion of the encoder. Your encoder has A & B. A1 connects to A2 and remains connected until you rotate it far enough to disconnect. Meanwhile, before A disconnects B connects. So let's think of switches as logic low and logic high. Low being an open switch and high being a closed switch. Both A & B are low. Rotate it (let's say) clockwise. A goes high. Keep rotating the encoder and B goes high. Keep rotating the encoder and A goes low. Keep rotating the encoder and B goes low. Keep rotating the encoder clockwise and again A goes high. The cycle repeats. If you rotate the encoder in the opposite direction B goes high, then A goes high, then B goes low, then A goes low. And so on.

To better address your project we need to know more about what you're trying to do. I can't tell you for sure there's a chip that decodes this sort of input but I'm confident there is one. Something like a Bi-Directional Decade Counter. May be called an UP - Down Decade counter. With each actuating of A & B the counter progresses in one direction or the other, depending on which went high first. But all that will do is simply count the number of clicks.

I have a couple encoders pulled out of an old stereo. They have something like 12 to maybe 21 counts per full revolution. I'm not home to grab one and test it, but that seems like the numbers I remember. Could be 12, could be 21. Maybe my dyslexia is kicking in again. .wonk t'nod I

Thread Starter


Joined Jul 13, 2019
I'm trying to create a 'volume controller' knob for my PC, is just a DIY project.
I have a old keyboard circuit that I use to send commands to the PC and there's basically two pins that need to be connected in order to send Vol+ and another two pins for Vol- command, so I thought that a rotary encoder would be great.

I know this can be done using Arduino + some programming, but I don't have one now and I'd like to use what I have to accomplish this.