Anyone use rotary encoders for feedback?

Good point when you are talking about incremental encoders that require external electronics to count the pulses.

But there are not many incremental encoders that can beat the precision of a 12bit hall effect pot, especially dollar for dollar. A 360 degree hall pot @12bits is equivalent to a 4096ppr encoder. But must people use only a 180 degree hall pot on their rig which is equivalent to a 8192ppr encoder. However, there is a little drifting of the output with hall effect pots where there is none with incremental encoders. Also, you need to have 12bit ADC's to realize the full 12bit output of the hall effect pots.

And unfortunately, with support for only one quadrature encoder on the Due, it is not going to be of much use for rigs using 2dof or more unless you use one Due for each dof.

I agree to every thing you say - but i have to add:

- There are dedicated encoder counter chips that support i2c or spi. - this way any micro will work and you can run more "dofs" per micro. (although i wouldn't bother, arduinos are cheap )
- The thing about the Encoder is you have "infinte" rotations so you stick it directly on the motor before any gear reductions. This gives a number of advantages such as motor rpm and vector feedback etc. in addition to the increase in precision. Encoders are used on CNC machines for this very reason.

So lets say you have a 10 to 1 gear reduction and a 1024ppr incremental encoder:
1024ppr = resolution of 4096 discrete positions per Motor Revolution. (Quadrature = 4x the ppr)
10x motor revolutions * 4096 = 40960 positions per output shaft revolution.

I use ball screws for my project and with a 360ppr encoder and i have 1440 positions per cm (3600 positions per inch) and "infinite" travel.

As for price, a quick search : http://www.aliexpress.com/item/Free...tal-rotary-encoder-600-lines/32221381502.html
these look very similar to the Omron encoders i'm using.

Cheers
/Daniel

I use JRKs, so don't have a choice, but is the extra resolution/complexity of an encoder actually needed/required in a DIY sim? IMO for most designs they would not be worth the trouble - you just don't need that amount of precision.

One thing worth trying is an Arduino Micro Pro using 2 instances of Encoder library (from Teensy's site). The Micro Pro is usually only about $4 and not much bigger physically than a pair of dedicated encoder chips, with the added advantage of being substantially cheaper and not needing an additional circuit board. If you don't already have a regular arduino or an FTDI cable, then something like an Arduino Nano (which has USB) or Teensy might be preferable. As long as it's simply doing encoding and conversion from incremental to absolute, it should handle quadrature data even before the gears (at thousands of RPMs). I wouldn't use to do additional stuff.

While I love Aliexpress, I found an amazing deal on eBay for mine. http://www.ebay.com/itm/171454356826
They shipped Very fast, were about the same price as Aliexpress, but included shaft couplers and bolts. The shaft coupling peaces are VERY nice, far better than I expected.
Right this second, the ebay seller is observing some Chinese new year holiday, so probably won't ship for a couple weeks. But when I ordered my 4 units a few weeks back, I received very quickly.

There are advantages and disadvantages when using hall effect pots as well as incremental encoders so I suppose it largely depends on your setup when it comes to determining which type to use. When using ball screws it makes perfect since to use encoders but not so much so when using wipers or other types of worm gear motors.

It is important to remember though that we are building simulators here, not CNC machines. Positioning resolution for a simulator doesn’t need to be anywhere near what is required for a CNC machine. The only real benefit I see to using very high resolution feedback on a simulator is possibly with a PID controller. Higher resolution means the PID will obtain new position information more quickly and that should allow for faster responses to changing conditions. However, I can’t say if it would make enough of a difference to even be able to notice.