For sure I am a travel addict. I am also lucky to have studied, worked and lived in various places around the world. My current stop is Singapore which is an excellent base for discovering South East Asia, a region full of hidden gems, diverse cultures and natural beauties. But I am no touristy-site hopper: when I travel, I try to look for small things, easily overlooked corners and places that are off the beaten paths. Small towns and cities are my favourite. It is in such places that you will find the most authentic food, untainted by the need to internationalize and commercialize, identify the unique aspects in the local way of life, and of course, meet the most friendly people who make your experience unforgettable. And I would rather spend more time in less places so as to give myself enough time to have a feel for whatever places I go to.

Interestingly, the more I travel overseas, the more I realize how little I knew about my country (I come from Vietnam), hence the need to go home and discover. Have you ever felt the same way? These days I try to make use of my limited holidays to explore what Vietnam has to offer. A highlight of this blog will thus be my travel experience in Vietnam and I hope it will be useful to travellers like yourself.

Enjoy!

P.S. Check out my tripadvisor reviews at http://www.tripadvisor.com/members-reviews/youngnfree

Incremental Encoder Pulse vs Count

Sunday, May 27, 2012

As a robotics engineer, I frequently work with packaging applications. Often, this includes having robots follow parts on a moving conveyor. This is possible with the use of encoders. Once an object is identified by a camera or a sensor, a trigger signal is sent to an encoder which then starts measuring the distance the object travels along the conveyor. Armed with this information, robots can predict when the object will get into their work area and chase after it.

Typically, the number one criterium when selecting an encoder for your application is resolution (or number of pulses per revolution of encoder shaft).

Naturally, you would want to select the highest resolution within your budget. The more, the better right? But that is not necessarily the case, as it depends on how frequent the receiving device can take in encoder pulses. Hence you need to pay attention to the minimum and maximum limits for the number of encoder pulses or counts such device can accommodate. In turn, this affects the size of your encoder wheel as well (if your encoder is wheel-mounted, as opposed to drive shaft-mounted).

At one point, I thought that the terms pulse and count refer to the same thing, but they don't. The fact is

Number of Counts =  Number of Quadrature Pulses x 4

You may also want to know that

Number of Counts Per Meter (CPM) 
             = Number of Wheel Revolutions per meter x Encoder Resolution x 4
Number of Counts Per Second        
             = CPM x Conveyor speed (m/s)

For those who want to understand various types of encoders, incremental versus absolute encoders, magnetic versus optical encoders, and more, below is an easy read from encoder manufacturer Dynapar. Just click on the picture.

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