Robotdyn is one of the few Chinese companies that managed to make a name for itself. They produce high quality Arduino clones and various electronics modules.
Today we review their 24 steps rotary encoder module.
Shop webpage: https://www.aliexpress.com/store/1950989
Rotary encoder
The first thing that pops of course is the price of the module. At About US$1, it is less than what you would pay for the raw encoder alone from typical suppliers such as digikey or Farnell.
That being said, what is annoying regarding this module -and generally speaking all Chinese products share this issue-: they don’t include any documentation.
After receiving the module I can tell with almost 100% certainty that the rotary encoder supplied is a Bourns PEC12R-4220F-S0024, or at least a very convincing copy of it.
This means this rotary encoder features:
- 20mm long body, 6mm diameter flat shaft
- 24 pulses per revolution
- Detent (the rotary encoder “clicks” at each of the 24 ticks)
- Built in switch (The shaft can act as a push button; and it clicks)
Here it is from Digikey, at US$1.25 for one:
Using the encoder
When you use a “module”, you expect it to be almost plug and play. Otherwise why would you bother with modules and not use the raw components? Here lies the real problem with this module: the difference between using a raw encoder and this module is abysmal. Robodyn slapped two 10k pull down resistors and a cosmetic green LED/1k resistor couple, and rolled with it.
This is a big issue because as a result, the output A & B (weirdly named CLK and DT on this board) are not debounced. During my initial tests, I noticed that sometimes the microcontroller would not interpret correctly the binary code due to these bouncing issues.
Fixing the module is fairly simple: some 100nF capacitors will work like magic on these pesky bouncing issues. However, it raises the question: why would you bother using these modules? You can simply build the resistor-capacitor circuit yourself.
Conclusion
I do not recommend this module. Until a newer revision with built in capacitors come out this module can hardly be considered a module at all. For now, it will remain a pretty encoder soldered onto a piece of PCB.
Note: after contacting the supplier, they said they will consider adding capacitors to the output.
 Score: Meh!
