Pololu Robotics & Electronics
Menu
My account Comments or questions? About Pololu Contact Ordering information Distributors

Pololu Forum

Micro Maestro Error - Resets Servos

Hi there!

I’m in the process of building a BB8 droid from Star Wars. The droid is fully functional with a moving head and body.

There are four servos and two motors that control his movement. I’m using a micro maestro to control the servos, but after some time of using the droid, I get an error. This error resets the servos and they no longer operate at their proper speed (they move at full speed). It’s not clear to me what is causing the error as it happens randomly. It looks to me like the LEDs on the maestro are blinking yellow with a solid red, but based on the user guide, this should not happen during normal operation. I will mention that this error seems to occur when I have multiple servos going, specifically the body tilt servo.

This happened when my maestro was at firmware version 1.02 AND 1.04, I will say though that the servos are surprisingly a lot smoother with version 1.04. I’ve had issues trying to smooth out the movement as well.

The servos are currently set to “off” in the control center. If I switch them to “ignore” will they ignore this error and continue to operate normally?

The maestro and servos have enough power as they are both getting 7.5v from an Arduino Mega so I don’t believe it to be a power issue. Restarting the droid fixes the issue, but with the servos at this speed, it knocks the head off BB8 which I really need to fix.

V1 Drive Wiring Diagram V1.0.pdf (1.9 MB)

Here is the wiring diagram. The servos are HiTec 9380TH except for the head spin servo which is a 2645CR

I will mention that this error seems to occur when I have multiple servos going

This is a clear symptom of an inadequate power supply. The HiTec servos each draw 2.1 A (the stall current) every time they start to move. If you have 3 servos moving at once, plan on a power supply capable of providing well over 6 Amps.

As an aside, the wiring diagram may look impressive to you, but it is nearly useless, as it is incomplete and leads, lead functions, pinouts and components are not properly labeled.

The battery is a pack of 10x 10000mah D cell batteries soldered together. I’ve checked the voltage and they are outputting the correct amount. This setup works with other members of the group I am with.

Something is wrong with your setup, because it is evidently not capable of delivering the current required by the servos.

This statement cannot be correct. A Mega cannot power servos.

Looking at the wiring diagram, power comes from the battery (12v) to a CC BEC Pro where it is converted to 7.5v. That is plugged into a custom shield on an Arduino Mega. There are two outputs from the shield to the maestro - one to power the maestro, the other the servos.

I just did another test and plugged he maestro into my pc after the error occurred. It’s labeled as a serial signal error.