Some electronic (not talking about old-old purely mechanical) control dials are “clicky” — there’s probably a better word for it; I don’t just mean that there is a click-stop/detent effect to turning the knob, I mean each click always gives a specific increment of control. Example: on a washing machine, if there are (say) twelve different cycle options, each one has its own certain detent, and when you reach that detent, you get that cycle. It doesn’t matter if you reach that detent by turning the knob slowly or fast; if you want whatever the seventh cycle around the dial is, you just have to glance at the dial and see where it is, then you can select your chosen cycle without looking: if the dial started all the way counterclockwise, you rotate it (fast or slow) through six click-stops. If the dial started two cycles to the left of your chosen one, you rotate it (slow or fast) through two click-stops. And you arrive at your chosen cycle every time.
Or on a dryer, if there is a dial to choose a time between 10 and 90 minutes, passing through each detent adds or takes away a certain specific number of minutes on the display, no matter how slowly or fast you pass through the detents.
Same on an oven with a dial to set a temperature between 95 and 290 °C; passing through a single detent adds or takes away a specific number of degrees (usually 5 or 10)…again, no matter if you slowly and deliberately cross each detent, or grab the knob and gave it a zesty spin.
With other control knobs that’s not the case, they’re more “stretchy” (again, probably not the right word). The volume and tuning knobs on my last two car radios from 2008 and 2016 have been “stretchy”, and same with two different washers, one from 2003 and one from 2020, and also a dryer from 2020: if you very slowly turn the knob you get one increment per detent, but if you spin it faster it sort of slips: you can hear/feel you went through a bunch of detents, but you only jump one cycle, or only add or take away a small number of dryer-minutes or a small amount of radio-volume. If you keep grabbing and spinning, you can eventually get to what you want, but you’ll rack up a big total of detents crossed.
*Or*, the opposite: if you turn the knob very slowly, either it doesn’t change the setting or it only bumps the setting by one increment after you’ve (slowly) gone through a whole bunch of detents, but if you grab the knob and give it a sharp crank, the setting goes to whichever end of the range you turned towards, even if you just crossed relatively few deteents.
What makes the difference in how these kinds of controls operate? Are they different kinds of devices behind the control knob? Different programming of the circuitry? Something else?
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Likely the largest difference is the mechanical apparatus responsible for the detents. Likely the positive clunky detents are metal and could even be gated at the different features along the dial.
The stretchy or mushy ones, are likely plastic, and just have a set of 20 or 30 tabs that the dial clicks along, that have nothing to do with where the features are located in the dial.
Don’t know if this answers your question, but I worked with software engineers in avionic controls and displays. The code which handled the input of a rotary knob, or for that matter, a simple up/down toggle switch could include what we called “ballistics”.
Say, for example, that the control sets a heading value (between 0 and 359 degrees). For a rotary, if the operator went through the clicks slowly, he was probably close to the value he wanted, and needed to go slowly to get it right. If, however, he went through several steps very quickly, the code understood that he probably had a long way to go and was “trying to get there in a hurry”, so we’d make bigger jumps for each step. Similarly, if we were using an up / down toggle for the same function, if he pressed it, we started moving slowly, but if he then held it down, we figured he wanted it to go faster.
The behaviors you’re describing in these knobs or dials are due to two types of technology used behind the scenes: Incremental Rotary Encoders and Potentiometers.
**Incremental Rotary Encoder -** The “clicky” knobs you’re describing are using a system called an incremental rotary encoder. It’s a type of sensor that converts the rotational movement into electronic signals which can be processed by a computer. Each “click” you feel corresponds to a certain amount of rotation of the knob, and the sensor sends a signal to the machine each time you pass a click.
In the case of your washing machine, the dial has been programmed to change the washing cycle with each click, no matter how fast you turn the knob. Similarly, on your oven or dryer, each click adds or subtracts a specific number of degrees or minutes.
**Potentiometer -** The “stretchy” knobs, on the other hand, often use a potentiometer. Potentiometers work a bit differently. They also convert rotation into an electronic signal, but it’s more of a continuous signal rather than a series of clicks.
So in the case of the volume or tuning knobs on your car radio, or the dials on some washers and dryers, the system is looking at both the speed and the distance you turn the knob. If you turn it slowly, it changes the volume or tuning slowly. If you give it a fast spin, it changes more quickly. That’s why you might pass through a bunch of detents but the volume only changes a little bit if you’re turning the knob slowly, or why the volume jumps to the maximum or minimum if you give the knob a quick spin.
These two types of knobs can feel different to use because they’re based on different types of technology, with different kinds of sensors and different programming. And they can each be useful in different kinds of situations, depending on what kind of control you need over the machine.
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