Servo Help

I love that CatBot! I'll have to try that myself some time

Thanks for pointing it out.

Is it possible that the Arduino is resetting, causing it to start over?

Cheers,

-Nico

How would I know if it is restarting?

You could print something to the serial port at startup. The serial monitor will then show if it restarted. More details on how to write to the serial port are in this Oomlout tutorial: products:ardx:circ-10[.:oomlout:.]

The serial printing is also a good way of debugging, to see what else might be going on.

Cheers,

-Nico

Typically the Arduino resets because the spike from the servo drops the supply, enough to cause a reset.

Motors tend to draw 2-4 times their running power when starting, hence they often overload the supply.

The instruction provides no extra filtering and depending on what Arduino you get, the results will vary.

The best way is to provide separate power to the servos, and join the ground together OR you can try adding a 1000uF (or larger) capacitor across the supply as close to the servos as you can.

To check for a reset, I would connect a LED (through a resistor) you could flash it three times in the void setup() part of the code.

This would easily let you know its doing a reset as this only runs once.

Mark

Typically the Arduino resets because the spike from the servo drops the supply, enough to cause a reset.

Motors tend to draw 2-4 times their running power when starting, hence they often overload the supply.

The instruction provides no extra filtering and depending on what Arduino you get, the results will vary.

The best way is to provide separate power to the servos, and join the ground together OR you can try adding a 1000uF (or larger) capacitor across the supply as close to the servos as you can.

To check for a reset, I would connect a LED (through a resistor) you could flash it three times in the void setup() part of the code.

This would easily let you know its doing a reset as this only runs once.

Mark

I'll hook up a 9 volt to the servos.  Thank you for the help on this.  This will help with my other project, and animatronic tail for my kids.

Glen

Just be careful with the 9v to ensure the triggering still works with only 5v.

In theory a HIGH is above the halfway point so should work.

This power issue comes up often, so you aren't the first, and won't be the last to encounter it.

A battery (which servos normally connect to) is a very large capacitor, but when you use a power pack and the on-board regulator, it isn't the same.

A general rule of thumb is to have 1000uF per amp of load. So for a single servo adding 1000-2200 (or larger) will only help.

If the load is high frequency (very short spikes, square wave or other digital) then adding 0.1uF (100nF) capacitors, across the supply, at the source (load) will stop it being a nuisance.

Mark

It's working great.  I added a dedicated power supply for the servos, 2 of them, and a cap across their rail.  I only had to tweet the angles a little to get the range I wanted.  This will go a long way to making my other project go smoother.

Glen

That's good news.

The advantage of this is that you'll probably never think twice about adding the caps, and your projects will be 'glitch free'.

Mark