Servo Motor Control Help

Thread Starter

Dlong88

Joined Nov 9, 2010
26
I am trying to build this circuit:

and it doesn't seem to be working for me, and I was wondering if I was reading it correctly. My electrical engineering is at a beginner level so be gentle...

I get no response at all from the servo motor, and I tested my 555 chip with a simple circuit to make sure it is working and it is... I don't understand how it isn't working.

Here is an attempt to draw a more specific picture of how I am setting this circuit up. I hope it is clear enough for you to understand.


Thank You
 
Last edited:

praondevou

Joined Jul 9, 2011
2,942
What are the component values? (All of them)

Is this a breadboard setup? Are the left and right "-" and "+" rails connected to each other? You can also post a picture.
 

Thread Starter

Dlong88

Joined Nov 9, 2010
26
Yea I am really sorry for the crappy picture. This is a breadboard setup, and a picture won't serve any help because it is a mess. Here is a website that I referenced:
http://www.aaroncake.net/circuits/servocon.asp
The positive rails are both connected to the same source as well as the negative. If you need any other helpful information please ask, I know this is not a lot to go off of.
 

Thread Starter

Dlong88

Joined Nov 9, 2010
26
I have a FUTABA S3003 Standard Ball Bearing Servo. I will read the links you have sent to see if it will help me.
 

Thread Starter

Dlong88

Joined Nov 9, 2010
26
Well I have looked over the advised reading and I still don't see why I cant get even the slightest response from the motor. So you guys are saying that the diagram I made is how the wires should be connected compared to the circuit diagram?
 

praondevou

Joined Jul 9, 2011
2,942
Check first if the 555 is working the way you have it wired now. You could put a resistor and a LED to gnd at the output.

Or use an oscilloscope.
 

Thread Starter

Dlong88

Joined Nov 9, 2010
26
Ok so where the signal output is for the servo motor I would put the positive end of an LED and then tie a resistor from ground to the negative side of the LED?
 

praondevou

Joined Jul 9, 2011
2,942
Ok so where the signal output is for the servo motor I would put the positive end of an LED and then tie a resistor from ground to the negative side of the LED?
Yes, from pin 3 of the 555 to anode of the LED, from cathode of the LED to the resistor then to Gnd. A 390Ohm resistor gives you about 10mA at 5V, enough to see if the 555 works. Adjust its frequency (timing resistor/capacitor) if it oscillates to fast (for testing purposes only).
 

holnis

Joined Nov 25, 2011
49
Also you should take care about the supply voltage of your servo. If it is powered with lower than 5V, you should add a zener diode accordingly.
 

djsfantasi

Joined Apr 11, 2010
5,702
In you picture, you have drawn the three wires to your servo as red, green and grey.


The red wire of the servo should go to 5 volts as shown in your picture. I am assuming that the green wire goes to the black wire on the servo connector. And that leaves the grey wire connected to the white wire on the servo connector and connected to Q1 on your circuit.

Is this correct? (This is where a picture would help.)
 

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Thread Starter

Dlong88

Joined Nov 9, 2010
26
ok well flipping the transistor didn't do anything, and @ djfantasi yes that is correct. I will try and clean up the circuit and take a picture.
 

Thread Starter

Dlong88

Joined Nov 9, 2010
26
I'm starting to think that my servo motor doesn't work.. I wish I could have some kind of fail safe way of testing if it works... I have another servo coming in the mail any day now so I will try replacing this servo with a new one.
 
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