I’m playing around with a servo I bought on a whim (just to play around with…), and I don’t seem to see the full range of motion I’d expect. I understand that the servo can travel 180 degrees, and if I rotate the servo by hand (hey, it’s a cheap servo…) I can see that the range of motion is indeed a bit more than 180 degrees.
Driving the servo with GHI’s class from code.tinyclr.com, however, I see maybe 120 degrees of motion. If I drive the servo with the HobbyServo class also available on code.tinyclr, I see roughly 90 degrees of motion.
What gives?
Thats ironic. I just finished writing up a project on “Rolling Your Own Servo Tester”. No need for $20-$40 tester. Already have a Fez, so save some money and have some fun. 
[url]http://staceyw1.wordpress.com/2011/03/26/roll-your-own-servo-tester[/url]/
I had same kind of issue with a medium DGServo bought at SparkFun. I found the limits to be around 0.69 - 2.435ms. I guess the take away is do not assume a standard of 1-2ms range. Most docs and code I see seem to assume the std figures. So test drive it, to find the actual limits. Also hold your servo during testing. You can hear and *feel any buz at the range limits. Adjust your limits as needed. This is probably a good practice as you don’t want to drive past servo limits just to buz and draw more current neadlessly. HTH
It certainly does. Oddly enough, it seems to get the full range of motion I must go fairly far beyond the mfr’s specifications: [url]http://www.hitecrcd.com/support/product-support/faqs/servos/general-servos/index.html[/url]
Is that normal?
Not sure. I suppose there is three reasons. Either the pwm output is not giving actual pwm values. Or, the servo mfg tolerance error. Or a combination of errors. Probably no matter. Once we find the limits in our actual world, the final numbers are relative. As long as servo gives you the range (~180) you need. IIRC the higher-end receivers/transmitters can account for this with their calibration and/or trim functions. HITEC is a high quality brand - right? Try some others out of interest. I will also.