SensingBench electronicsTest and identify
Linear encoder strip
Also called encoder film, printer encoder, codestrip.
The clear plastic ribbon in an inkjet, printed with fine dark lines, read by an optical sensor on the carriage. It is a real linear scale. Fingerprints and creases destroy it.
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 |
|---|---|
| Pitch | Often in the 150–180 lines per inch class on consumer inkjets. Some are finer. Count lines over 10 mm with a loupe; do not trust a memory. |
| Sensor | A small optical head on the carriage, usually 5 V, quadrature outputs. Keep the head with the strip. |
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
- Position feedback on the same travel the printer had
- A dro for a small axis, if you can keep the strip flat and the head at the right gap
Leave this one when
The strip is scratched, inked, or stretched. You will chase a phantom position error forever.
Buying a new one is the better idea when
A commercial scale, if the travel or the accuracy is a specification rather than an experiment.
How to tell if this one still works
Power the head the way the printer did (look for a 4- or 5-wire flex: power, ground, A, B) and move it along a clean section while watching the outputs.
Tools you will want: Loupe, 5 V, Scope or microcontroller.
Words on this page
Short meanings, so the rest of the entry is readable if you are not already doing this every weekend.
- quadrature
- Two signals slightly out of step, so a circuit can tell which way something is turning, not just that it moved.
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 |
|---|---|---|---|---|
| Inkjet printer | Prize | 1 | usually | Parallel to the rod, clear plastic. |
- In this particular machine
- A linear scale. Pitch varies; count it.
- Where to look
- Parallel to the rod, clear plastic.
- How to get it out
- Do not fingerprint. Store flat or in a tube.
- The condition to expect
- Useless once creased.