SparkFun Forums

[peterrand]

When a servo is driven by a Pro Mini with the simple 180 degree sweep program example provided (// Sweep
// by BARRAGAN <http://barraganstudio.com>) it rotates only about 90 degrees.
When the same servo is driven by the Arduino Duemilanove using the identical program and setup, it rotates 180 degrees as "advertised".

The same thing happens if the write parameter for the servo is in microseconds instead of degrees.

This has been found for more than one Pro Mini.

It is as if the Pro Mini CANNOT supply the pulse widths necessary to get the full angular range the servo can give. This is a major shortcoming and makes the Pro Mini NOT equivalent to the other Arduino boards.

Is this a common problem that others have found? Is there a fix?

[SFE-Robert]

Which pro mini are you using?

Are you using an 8mhz or a 16mhz?

[phalanx]

I'm guessing you are running at a different frequency as well. I know the purpose of the Arduino is to be able to hook up and go but its never wise to rely on someone else's design without verifying it for yourself.

-Bill

[peterrand]

Thanks guys - yes - mine is the 16Mhz Promini but that is not an board option for uploading a the pro mini - But if one uses the Duemilanova board for uploading programs the Promini 5.5 volts works a charm - whoda known??

[TS-Feedback]

What is your power supply? Sometimes if the power supply can not provide enough current for the servos, you will see similar performance.

[peterrand]

power supply is 6V regulated capable of 1000ma - not the problem - it was uploaded for the wrong frequency as noted above - thanks

[SFE-Robert]

Thanks guys - yes - mine is the 16Mhz Promini but that is not an board option for uploading a the pro mini - But if one uses the Duemilanova board for uploading programs the Promini 5.5 volts works a charm - whoda known??

From the product page for the Pro Mini:

"For the 5V versions of the Arduino Pro Mini, select Arduino Duemilanove or Nano w/ ATmega328"

http://www.arduino.cc/en/Guide/ArduinoProMini

It is essentially just a small Duemilanove. I think version 18 of the IDE has Pro Mini's in there. Not sure though.