Servo issues - odd behavior in 360 degree servo

Hi all,

I have been struggling a little for a while now.

I used to have a fully functional Arduino based 8mm scanner with two servos on itl. I powered the Arduino and the servos from one 9V 1.5A power source, and the camera from its own 3.3V 1.5A power, and the lamp from its own 4.5V batteries and all was well.

Now my servos and Arduinos are all odd. if I connect a 180 degree servo and run the Sweep example, all is well. When I try to swap to one of the very same servos I had, and run a tiny script that I use to rewind the film, I get the USB disconnect sound on and on and the servo doesn’t do anything.

Sweep working:


360 degree not working:

360 degree

And the code for the 360:

#include <Servo.h>
Servo myTransportServo;
void setup() {
void loop() {


I am baffled to say the least. Any assistance greatly appreciated.

I would try powering the servo separately from the arduino.
4 AA batteries or similar. Connect the grounds.

I am just really surprised how I used to run not one but two 360 servos off an Arduino receiving 9volts from a regular battery… and now not even one works.

I am not familiar with that shield.
It does have a power-in set of pins in the lower left. Blue screw terminals.
It does not look like you are using them.
If not, then you are powering the servos from the arduino’s 5v regulator, which simple cannot be relied upon to drive physical motors.
Power your servos independently from the arduino. Common ground.

Consider running an experiment without the shield.
Make it look something like this:

Oh, I know, the 9v batteries like that are useless. Power your arduino like you have been. But power the servos from a separate source.

Let us know how this works out.

This looks great, I'll try it out straight away. Many thanks!

I just can't understand why it used to work and does not work anymore.

Yes indeed, you solved it! Many thanks! I will now start rebuilding the entire scanner based on this idea.