SensingBench electronicsUnplug and unscrew
Quadrature encoder
Also called scroll encoder, rotary encoder, mouse wheel.
Two out-of-phase switches or optical sensors. The mouse wheel is the common one. Direction comes from which channel leads. Resolution is coarse, which is fine for a knob and useless for a CNC axis.
If you are new to this category
A sensor reports a condition such as weight, light, temperature, or position. Many sensors do not switch fully on or off. A kitchen scale bar, for example, changes by thousandths of a volt. Keep the small board that read the sensor if you still have it.
Keep the connector. Write down the wire colors before you cut them. If you do not know which wire is which, the sensor is hard to reuse.
Red and black feed the sensor a steady few volts. Green and white are the tiny signal, measured between them, not from either one to ground. Pressing the bar changes that signal by millivolts. A normal meter on DC volts can show that it responds. Turning it into a number on a screen wants a small amplifier board, often an HX711.
| What to look for | Usual figure |
|---|---|
| Mechanical | Two contacts to a common, bouncing, needs software debounce or a proper RC |
| Optical | Inside some mice and most printers. Cleaner, needs power. |
| Detents | Often one detent per pulse on a scroll wheel. Count them. |
Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.
What people actually use it for
- A user knob
- A jog wheel
- Measuring slow rotation
Leave this one when
The detents are ground to dust. Mechanical encoders wear out; that may be why the mouse felt bad.
Buying a new one is the better idea when
A panel encoder with a known pulse-per-rev, once it is a product.
How to tell if this one still works
Beep or scope both channels while turning slowly. You want a clean gray-code pair, not two copies of the same click.
Tools you will want: Meter or a microcontroller.
Where people actually find it
1 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.
| From | Call | How many | How often | Where it sits |
|---|---|---|---|---|
| Optical mouse | Worth it | 1 | usually | The wheel. |
- In this particular machine
- Mechanical quadrature, coarse.
- Where to look
- The wheel.
- How to get it out
- Keep the wheel and the encoder as a unit.
- The condition to expect
- Worn detents are common.