Hello world,
I'm an engineering student, and I'm currently thinking about how to build my 3D printer and so, I need motors to power it. I plan to use DC motors (As in this article : Stepper Motor Emulator (Part 1) - Circuit Cellar), which are said to be less prone to errors, and above all cheap (Can even be taken from old devices). So, I need a rotary encoder to correct the motor position.
Here comes my problem. I need a separate encoder, firstly because I can't find a motor/encoder couple that suits me (Or too expensive), and secondly because the motor will be geared down, so I would prefer to have the position of the output shaft without having to recalculate the ratios every time.
I have been looking for something like this:
In which I can just plug my shaft, but I couldn't found any ! Maybe wrong keywords (I'm not an english speaker) ? I don't know, but if someone could give me a link to a good encoder matching my needs, and especially not too expensive, I would be really gratefull...
Thank you for reading me 
the printers, laser or inkjet, have few such encoders motors.
Hello,
Whow, it's probably the fastest response I have ever seen on a forum, so, thank you
I knew it, but there are not printers to dismantle on every street corner 
I was also thinking that with something commercial I could choose the precision (On the site they speak of 88 PPR), and that I would have manufacturer data on how to connect it to the arduino... No? Then suddenly the sensor will be on the primary shaft, not the output shaft
take DC motor what you has. in 1$ shop buy an optical mouse. take his sensor and connect to Ardu. let it scrolling on some surface and you will become precision of 6000-12000 DPI.
Amazing the idea But can you explain to me how the mouse works? Because with an optical encoder I see, you have a light source on one side, a receiver on the other and the disc in the center causes cuts which correspond to a pitch. But by dismantling a mouse I will just have a laser transmitter, right ? How do I convert this to angular position ?
Like all the relatively inexpensive ones I found on Aliexpress.com, that seems to have the encoder on the motor shaft, not the gearbox output.
If a DC motor+gearbox+encoder+H-Bridge driver was cheaper and more reliable than a stepper, I would expect more 3D printers to use them.
Don't you think it can be ? Even if you find motors somewhere, and 3D print the gearbox ?
Because stepper are really expensive. I mean, maybe not for a 18cmx18cm 3D printer, though, but when you begin to need more torque...
@kolaha was probably talking about the ancient mouses (the ones with a heavy sphere mechanism). Those ones were based on two optical encoders. One for x axis and one for y axis.
Well, yes, I´m getting old. When I was at university, USB ports didn´t exist. 
This article (parts I and II) is heavy on theory, and results are nonexistent. Take it with a large grain of salt.
The author does not show any actual wiring, code, or any results from motor tests, let alone actual use of a DC motor/encoder in a 3D printer.
All the code is on github (GitHub - misan/dcservo: Position control of DC motors) with some additionnal informations. If I remember well, in the end of the second article he says he has been contacted by many people who have done this, and that they have been quite happy with it...
Didn't know about rolling mouse, last time I saw one I was 9...
No results, though. Have you made any significant progress with this?
Me ? No, I'm not home before the end of april, so I can't test anything. But a project forked 107 times... Has anyone one the forum tried it ?
There is also the Mechaduino project which use the same idea, and wich is perfect for a 3D printer. But if designed to be "affordable", it's far to mean cheap...
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