Optical Linear Encoder - Page 1
Forum section: electronics / projects

author: Lunat1c
author_rank: Contributor
timestamp: March 08, 2012, 06:31:15 pm
content: Does anyone know somewhere in Europe where I can buy a good optical linear encoder to use to keep track of the distance travelled by the head of a printer (which I'm using for a project)? I tried figuring out how to use the one that comes with the printer itself but with no success because firts of all I don't know its resolution and ofcourse I have no datasheet of the component.Any help will be greatly appreciated. Thanks!PS: I'm not looking for something which is very expensive. It's being used in an application of vertical stabilization where I need a certain degree of precision

author: sacherjj
author_rank: Frequent Contributor
timestamp: March 08, 2012, 09:15:18 pm
content: As long as the speed isn't too fast (which I worry about for a print head) you could use an inexpensive digital micrometer. I've done this in the past with some 12" calipersmicrometersfrom Harbor Freight (a Chinese Importer in the US.) They have a serial data port where you can read the data and I believe I was about to trigger a remote zero. (It has been a few years.) This was used in a pair for an accurate X Y positioning system for a drill.

author: robrenz
author_rank: Super Contributor
timestamp: March 08, 2012, 09:32:10 pm
content: Quote from: sacherjj on March 08, 2012, 09:15:18 pmI could be wrong but I think you meant calipers not micrometers. Most are limited to .01mm resolution. Mitutoyo has absolute versions where it does not loose its zero even when turned off (battery is still powering the unit). If you google caliper based digital readouts there are a lot of examples.

author: sacherjj
author_rank: Frequent Contributor
timestamp: March 08, 2012, 09:55:11 pm
content: Quote from: robrenz on March 08, 2012, 09:32:10 pmYou are indeed correct. I fixed my post. The print head would have to go VERY slow for micrometers to be of much use. We ground down the caliper arms and put a screw through holes in each. As long as you are on axis flat, this deal with any slightly off axis along the linear scale.

author: robrenz
author_rank: Super Contributor
timestamp: March 09, 2012, 12:52:29 am
content: If your printer uses a pulley or capstan drive it will probably be cheaper to use a rotary encoder on the rotary element, you would need a multi turn model or count turns in software. This will not be as accurate as the direct coupled linear encoder but may be enough for your needs. Resolution may be an issue with a digital encoder (2 square waves in quadrature) but if you use a analog encoder (2 sine waves in qaudrature) you can use iterpolation methods to get finer resolution

author: sacherjj
author_rank: Frequent Contributor
timestamp: March 09, 2012, 03:27:58 am
content: Quote from: robrenz on March 09, 2012, 12:52:29 amThis would also solve the speed issues that you would run into with the linear encoder.

author: Rudolfo
author_rank: Contributor
timestamp: May 12, 2012, 10:14:11 am
content: If you want to build your own encoder you hight take a look at this White Paper with magnetic and optical solutions using single chip encoder:http://www.ichaus.biz/wp_boost_performance.

author: G7PSK
author_rank: Super Contributor
timestamp: May 12, 2012, 03:01:48 pm
content: What about these people they have several different types available.http://www.machine-dro.co.uk/digital-readout-systems.html

author: sonicj
author_rank: Frequent Contributor
timestamp: May 14, 2012, 01:11:59 am
content: does it have to be optical? what about hall effect?-sj