optical rotary encoder for position feedback - Page 1
Forum section: electronics / projects

author: JBeale
author_rank: Frequent Contributor
timestamp: November 23, 2014, 05:10:55 pm
content: After being annoyed by the noise from stepper motors, I've been looking into using DC motors with encoders for position feedback in my robot project. (For any useful torque, usually you need a geartrain which is also noisy, but I'm ignoring that for now.)In case of interest: Ebay has "photoelectric rotary encoder" starting around $15. These have two outputs in quadrature so you can tell the direction of rotation as well as the angle. I got a 600 pulse/rev and a 360 P/R model, the latter is in the photos below. Inside is a metal wheel with many thin slots. I wasted some time because I don't read Chinese and relied on the (wrong) pinout listed on the Ebay page. I had to take it apart to find +Vcc (5V) was the white wire, not red. Then tried translating "white" into Chinese with Google Translate. With correct hookup it works. The spec says 5V but it works down to Vcc = 2.6 V. The label says VCC: ? (white) GND: ? (black) Channel A: ? (red) Channel B: ? (green)

author: CM800
author_rank: Frequent Contributor
timestamp: November 23, 2014, 05:57:01 pm
content: That soldering looks like its been done by a 12 year old (to be honest my 11 year old sister solders better then that)

author: KG7AMV
author_rank: Frequent Contributor
timestamp: November 23, 2014, 07:21:59 pm
content: Look at this encoder... EPC 15S-19M4-2000N5ROC-F00http://www.encoder.com/literature/datasheet-15s.pdfthe china optical encoders are very poor quality and it looks to be missing the 2nd sensor?

author: SeanB
author_rank: Super Contributor
timestamp: November 23, 2014, 07:32:47 pm
content: Quote from: TCWilliamson on November 23, 2014, 05:57:01 pmTo be fair it probably was done by one, in a hurry, with another thousand to do before going off work to eat and sleep a little.

author: JBeale
author_rank: Frequent Contributor
timestamp: November 23, 2014, 09:57:56 pm
content: Quote from: KG7AMV on November 23, 2014, 07:21:59 pmI am sure the Made-in-USA encoders are good quality, but they are typically 3x to 10x more expensive than the Chinese stuff on ebay. The two I have work exactly as specified (after I understood the pinout issue) and they're good enough to play with for my present hobby purposes. Yes, the soldering is poor. This one has one module containing a detector pair giving the quadrature output. I doubt it was intended to have two detector pairs, more likely they just laid out an alternate part footprint so they could stuff whichever item was cheaper that week.

author: dannyf
author_rank: Super Contributor
timestamp: November 23, 2014, 10:07:36 pm
content: QuoteThe same can be said about your Chevys, Fords, or Buicks, vs. BMWs or Benz, or Bentleys.Are you willing to pay the BMW/Benz/Bentley prices for BMW/Benz/Bentley quality?

author: Kjelt
author_rank: Super Contributor
timestamp: November 24, 2014, 08:18:46 am
content: Quote from: JBeale on November 23, 2014, 05:10:55 pmAfter watching"automata"yesterday I think a robot making noise so not to be able to sneak up silently behind you is a good thing, a definite requirement

author: ConKbot
author_rank: Super Contributor
timestamp: November 24, 2014, 12:16:36 pm
content: Quote from: dannyf on November 23, 2014, 10:07:36 pmNot sure what youre on about with MB reliabilityhttp://pressroom.consumerreports.org/pressroom/2014/10/my-entry.htmlIn the US at least, only thing they are better than is most Chrysler group vehicles. BMW is only a bit better than average, so its just paying more to think youre getting better. (which is also a problem on ebay too)

author: SL4P
author_rank: Super Contributor
timestamp: November 25, 2014, 04:40:29 am
content: Apart from the obvious comments about soldering and quality - I'd be sure to blow out the optical cavity before you re-assemble that unit. The dust and swarf visible in the photo will guarantee at least some miscounting over the life of the device.