ArrBot: Dual Servo Calibration

Here's the process we'll use to calibrate the servos.  In phase 1, we'll do this the simplest way possible. There's two reasons for this:

• Practically, we're coding the first iteration in a limited amount of time.  Tending towards simplicity is a good thing at this time.
• For teaching purposes, it's good to have a couple of small single-purpose programs.  Later we'll combine everything into one program and put a cross-platform GUI.

Measure the Left Servo

Load the  Basic ArrBot Servo Tester.  There's a couple of values we're trying to find.

• Find the midpoint where the servo is stopped.  Write down this value as MID.
• Increase the value until the servo is at its maximum speed. Write down this value as HI.
• Decrease the value until the servo is at its maximum speed in the other direction.  Write down this value as LO.
• Calculate SPAN as HI - MID.
• Hopefully, SPAN = MID - LO as well.  If not, choose the lower balue.

Measure the Right Servo

Get MID and SPAN for the right servo as above.

Write the Calibration Data to the Arduino

• Grab the Basic Servo Calibrator.
• Fill in MID and SPAN for the left and right servos.
• Don't worry about REVERSE.  You may need to set that later.
• Run the program and the calibration data will be written to the EEPROM.
• Watch the serial monitor and it will confirm.

Now we're going to switch things up a bit.  First, we want to start thinking of motor speed in terms of percentage.

• -100% = maximum speed reverse
• 0% = full stop
• 100% = maximum speed forward

And we want to see if  if the two servos are working well together, i.e. if -100%,0%,100% produces the same speed on both motors.  We'll modify our servo test in two ways:

• Add a second servo control.  Now we can test the left and right servos at the same time.
• Change the control values to percentages.

Assemble the Enhanced Servo Tester

Start with the ArrBot Servo Tester. Duplicate the connections, so you have this configuration:

• left servo: RAW, GND, Pin 9
• right servo: RAW, GND, Pin 10

This will be the basic ArrBot configuration.

Test the Two Servos Together

Run the ArrBot Dual Servo Tester (coming!)  It has the following controls.

• v -- variable sweep from -100% to 100%
• c -- set 0%
• j, k -- subtract, add 1%
• r -- cycle through channel reversal combinations

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