Electronic – Driving a Servo a Motor

First, let me say that you didn't give enough information to say for certain what's causing the problem. Not a big deal, really, except that you have to understand that my answer may not be 100% correct.

The link to the Hobbico web site doesn't give much information about that servo. I "think" it says that it will pull 0.7 amps when running without a load. If this is the case, then you can assume that at startup or with a load (a.k.a. plate) it will consume more than 0.7 amps. This amount of current does not seem high to me, given the large size of the servo.

What we don't know is just how much more than 0.7 amps does the servo consume. A good guess is, "way more than 0.3 amps more". What this means is that you are likely drawing more current than what the 1 amp power supply can provide.

There are several things that could happen when the servo tries to consume more power than is available. Odds are that one or more of these things is happening:

• Power Supply (PS) output dips, causing a loss of torque in the servo. This will make the servo stick until pushed.
• PS output dips, causing the control electronics in the servo to reset.
• PS output dips, causing the Arduino board to lock up or reset.
• PS detects a fault and shuts off. It might turn back on immediately, or after a while, or not at all until it is unplugged and replugged.
• PS gets damaged.

The simple way to see if any of this is happening is to put an o-scope on the output of the power supply. While you have the o-scope out, you might as well look at other signals, like the signals going to the servo. You could also try a different, more powerful, power supply but that is less informative.

I still would try to use a microcontroller, that's going to be the easiest solution. Do you plan to remove the sensor inputs and the servo output from the controller? That will give you 4 extra pins. Isn't there a device in the same microcontroller family with a few more pins?

Alternatively you could use a small separate microcontroller to handle the sensor data and servo. That will be more compact, cheaper and easier to control than solutions involving 555s and what mores.