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Rotary switch w/ direction based contacts?? Answered

I'm looking for a specific type of switch... I believe that it must exist, but I have never seen it... I need a rotary switch, where each clockwise "click" (partial turn) makes one circuit momentarily, and each counter-clockwise turn makes a different momentary conection... example with two light bulbs ( L1 and L2 ) connected to each direction of travel, respectively: If you rotate the knob one "click" (say 15 degrees) clockwise, L1 flashes for a moment, as the knob is in motion. if you continue clockwise, L1 will flash at each "click". If you rotate the knob one "click" counter-clockwise, L2 flashes for a moment. if you continue counter-clockwise, L2 will flash at each "click". There is no center-point, so any clockwise travel corresponds to L1, and any counter-clockwise travel corresponds to L2. does anyone know where I could get a couple of these??



3 years ago

I'm looking for the same thing - and it's not a rotary encoder. The sequential bits needing decoding (as described by others) are called gray code. My use case is to literally replace two momentary contact tactile switches in a volume control. So, right now I have two buttons; volume up and volume down but I prefer a knob for volume, so I want a rotary switch that effectively presses volume up when turned clockwise and presses volume down when turned counterclockwise. It has to be momentary on each click (as opposed to open circuit on one click and closed on the next) because the existing buttons have press/hold functionality, which, as you can guess, keeps increasing the volume when held, and I obviously don't want that to happen half of the time ;-)

I could swear I saw one (as in 1, a single part) in some electronics supplier's website when I first started looking. It was expensive so I passed it by. Had I known that it may well be the only one of its kind on the planet... ;-) Anyone have any ideas what to search for? "Rotary encoder" is not it (don't want gray code) and "rotary switch" isn't it either (fixed number of choices based on position)

ok, maybe a rotary encoder is what I need, and maybe it isn't... I saw one site that referred to a rotary encoder with a "direction of travel" signal that was high if the encoder was turning clockwise, and low otherwise... if there were two of these pins (one for clockwise, one for counter clockwise) I'd be fine... what I was envisioning was a dual ratcheting system, where there are wedges in the plane of the knob facing one direction, and perpendicular to the plane of the knob in the other direction.... a flexible conductive stalk would ratchet in and out from the wheel when it turned one direction, bridging one set of contacts, and up and down when it turned the other direction, bridging a second set of contacts... just a thought


10 years ago

You're looking for a 'rotary encoder' switch...they are commonly found in many things (radios, etc.) but not so easy to find.

Digikey probably has them, but if you are in Europe, the shipping will kill...

You describe a relative-position switch. These are normally two-bit encoded. When you turn one direction = (01), turn the other = (10), no movement = (00), so usually some sort of digital decoding is necessary (micro controller, etc.) I have never seen one that works as simply and easily as you describe (a single switch for each direction) but they might exist.

Mechanical devices sometimes present the bits sequentially, i.e.:
(00)..... for stationary
first (10) then (01) for left
first (01) then (10) for right

I scavenged one from a bricked car radio, and it works like that. It also needs to be decoded.

Absolute-position encoded rotary switches have a larger bit field and are much more expensive.

does a rotary encoder output in serial or parallel? i.e. is 01 power to one wire, ground to the other, or is it a tx/rx signal? what sort of pinout would I be looking at?

The encoder I have is parallel, in the sense that it has two active leads and one common. As it's mechanical, the common can be gnd, source, etc.

On the other side there are two leads for the momentary switch (when the encoder shaft is pushed.)

Here's a PDF that illustrates everything nicely...


10 years ago

A rotary encoder will typically require some external "decoding" to produce the sort of "pulse here for click in one direction, pulse there for click in another direction." The actual output tends to be square waves, and you decode direction from the relative phases. Most "rotary encoders" produce a LOT of clicks for each rotation. Computer mice used to use them, then they used mechanical/optitcal versions, and now they're all optical (and not at all rotary...)