Wednesday, February 10, 2010

Worlds Most Useless Machine Build - Part 3

Building My Own Version of "The World's Most Useless Machine"
Part 3 - Obsessed Much? 
Louise has been pointing out to me that I have been totally obsessed with this project. I admit it I am! But on the plus side I am having a ton of fun designing it and have been learning new tools (electronic types) and refreshing my skills. It's been a very long time since I just played with electronics rather than working in the field for a living. I have forgotten how much fun it is to design circuits which is why I went to school after all.

So one item on my design list I can cross off is how servo motors work. I was rather surprised how little is written about how they really work on the web. Lots about mounting tips and what controllers to use but very little about the guts of the motors. I was curious so I kept digging and found a few pretty good sites:

***** NERD ALERT ***** 

 Read the following section only if you are a nerd like myself LOL

The second site gave me a big clue about how torque was generated in a hobby servo motor and why one direction will have more than the other director. This is important because on the Useless Machine one direction will be moving the control arm up to turn off the power switch and needs more torque. Basically the position of a hobby servo motor depends on the length of a pulse between ~1ms to 2ms is. A pulse of ~1.5ms will put the servo position in the middle of it's range. The range is typically 180 degrees of movement. The direction the servo moves with the long 2ms pulses is the direction to chose to the switch.

***** END NERD ALERT *****

So now with a better understanding of how hobby servo motors work I can go about designing my control circuit.

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