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R/C Related Electronics DIY DIY R/C Electronics for tinkerers and the budget minded


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Old 01-31-2011, 02:07 PM   #1 (permalink)
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Lightbulb DIY cheap and easy servo tester

While I was playing with my prototype board today, I quickly made a basic servotester, just for the fun of doing it, and because I had al the parts laying around anyway in my spare parts box.



Now we already know from this earlier thread https://www.helifreak.com/showthread.php?t=263175 that a common servo needs a framerate around 50 Hertz, but this is not critical at all. The pulse width is though, and most radios generate a 1 to 2 ms pulse, at a 100% rate. This can be a bit more, when setting the radio at max value, like 150%. And servos indeed accept pulses from around 0.7 to 2.3 ms pulses for full deflection, but still without damage to the servo at the endpoints.

Simply changing the resistors and capacitors in the testcircuit is enough to get almost any range you want. This testerís framerate is around 45 Hertz, which is enough, and pulse width can be changed from 3 to 9% in this case, thatís around 0.7 to 2 ms. Peak voltage of the square wave is 4 Volts, with a power supply set at 5 Volts (that would be your BEC normally).

Hereís a short vid, using a small Hitec S55 servo. The small oscilloscope is only there to confirm and measure the signal. You can change the pulse width, and of course the servo deflection with the potmeter.

[ame]http://www.youtube.com/watch?v=PaQuZRqxmOw[/ame]

And hereís the diagram, the 555 integrated timer circuit is the most popular chip in the world, and itís very cheap. This must be the most simple servotester anyone could build.

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Old 01-31-2011, 02:36 PM   #2 (permalink)
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Cool!! Scale speed retracts! hmmmm....
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Old 02-03-2013, 01:21 PM   #3 (permalink)
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Default A little HELP Please?

Hi,
I have only just come across your post yesterday and I am trying to build a copy of your design but for another purpose.
Anyway, my question is,
1. Does pin 2 of the timer i.c. connect to pin 6?
2. Would it be alright if i subtituted the caps. for those of a larger value? (if what you specified are not available at the time for me)
Thanks,
Jerry.
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