Servo Motor Control Using 555 Timer (Motor Rotates Unpredictably)

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SJialat

Joined Nov 22, 2020
1
Hi I am a beginner and I am trying to learn how to control a servo motor using a 555 timer! I am trying to recreate the circuit I found in this video:

However, the servo motor in my circuit keeps rotating unpredictability (instead of rotating clockwise/anticlockwise when the corresponding button is pressed). It is extremely hard to troubleshoot as each time I try the circuit out, the motor goes haywire in a different way (e.g. sometimes it doesn't turn at all, or it turns really slowly, or it turns really quickly and uncontrollably in the wrong direction)

The video I referenced comes with a diagram: https://drive.google.com/file/d/1qSqfs2S6xNHnJpvJRfDQkZwxaoELau7D/view

This is my circuit, I believe that it tallies with the diagram:Photo 3.jpgPhoto 2.jpg

Any help would be appreciated! Thank you!
 

wayneh

Joined Sep 9, 2010
16,568
Without digging too deeply into this, my first question is, How certain are you that your motor is a servo motor as intended for the circuit?

I'd be tempted to put the motor aside and use a 6V lightbulb with a diode in series for testing. The lightbulb could be used alone but adding the diode will tell you about the polarity. This might help you sort out where the problem is.
 

djsfantasi

Joined Apr 11, 2010
7,251
Hobby RC Servos are controlled by PWM at a fixed frequency. The most reliable controllers use two separate 555s. One to set the frequency and a second one to control a variable pulse width.

Single 555 circuits depend on the hobby servo responding to a range of frequencies, because with one 555, the frequency changes with the pulse width.

This works often enough so that there is a plethora of designs that use one 555. But their success depends on the servo. They don’t work with all servos. If you were to get another servo from a different manufacturer, your controller may just work.
 

AlbertHall

Joined Jun 4, 2014
10,792
One point which may be worth mentioning is that you must keep either one of the switches closed. You can't press one button and then release it.
 
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