Project Astromech, a 2 Geeks Web Design Presentation

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Dome Hardware

Dome Electronics

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Body Electronics

Leg Hardware

Leg Electronics

Other Electronics

A collection of build posts related to the construction and design of our Astromech’s three legs and propulsion.

After the problems I had with my second motor controller in my last post , I received my replacement controller from Pololu and quickly assembled it. This time, everything went perfectly and I was able to test its function.

Now that I had two working and tested Motor Controller and Foot Drive pairs, I set off on setting up a quick test platform to see if I could get Artoo’s Differential Drive System working via RC control, and maybe see him take his first steps.

I wired the components together (see diagram) on a small piece of plywood to create a small testing platform that I could mount a 12V 18AH SLA Battery, the RC receiver, 2 motor controllers, and two drive motors.

Before I was able to establish positive RC control, I first had to use Pololu’s diagnostic and control program to configure each motor controller. Our set up uses a single stick of the RC transmitter to control both throttle and steering. Therefore, we have to set each channel to operate correctly on both boards. This was accomplished simply by using the channel configuration wizard in Pololu’s application.

For the most part this was a very simple process, however there was one issue that arose that I hadn’t given much thought to. While testing after the initial configuration, I realized that each wheel in the foot drives was turning in an opposite direction. During my initial testing on the bench, I had the foot drives oriented in the same direction and thus never realized it. Artoo on the other hand has his feet aligned in a way that both motors are facing towards his center, requiring each motor to turn in an opposite direction in relation to the other in order to move forward or backward in unison. I could have simply reversed the power cables running to one drive motor but didn’t like the idea of running a red wire to the black lead of the foot drive. Call it OCD, I just feel it is safe to keep things simple to avoid future complications, Red to Red, Black to Black.

Pololu’s software however offered a simple solution. I was able to configure each channel on one of the controllers to operate inversely, thus correcting my predicament and allowing the drives to operate both forward and backwards in unison.

Now that I had the test platform working on the bench, it was time for Artoo to take his first steps.

While it will take some getting use to, I was able to positively control forward and reverse movement, as well as left and right steering.

Artoo requires at least 3 different motors, two of which are paired together, to achieve both ground locomotion and dome rotation.

As discussed in my previous post, , I plan to use two Pololu Motor Controllers to drive my Midwest R2 Builders Club DDR Foot Drives for droid mobility.

Additionally, I plan to pair a Syren 10 Motor Controller with an R2ATL Dome Drive Assembly to handle Artoo’s Dome Rotation.

Since I know very little about Motor Controllers, I began by sifting through the documentation on the Pololu website trying to figure out how to set these up correctly. These controllers have an on board USB interface that allowed me to use some diagnostic and control software to test the Controller/Motor Combination before connecting them to the RC Control. This proved to be quite handy as the RC configuration and wiring is a bit more complicated due to the channel mixing required for Artoo’s Tank Drive System.

I quickly installed the software and drivers on my extra windows laptop (No Mac Version) and got to work setting up the test wiring configuration seen here. Once I was sure every thing was correctly wired up, I connected the motor controller to my Laptop via USB and the power cable to my 12V Battery. I openedd the Diagnostic software and was happily greeted with zero errors and system ok display. I used the manual slider with in the program and was able to easily control my motors forward and reverse rotation.

With one success behind me, I began to wire my second 18v25 controller and motor in the same fashion and hooked it up for testing.

Unfortunately, the board fried immediately and I was engulfed in the stench of burned electronics. Looking over the board, I quickly found that one PCB path way (I have yet to learn what they are called) burned up entirely through the top layer of the board.

I have no idea what caused this but it could have very well been a bad solder job on my part as I will be the first to admit I haven’t perfected my technique yet and this board was especially tight. I have a support ticket in with Pololu and we will find out how that pans out soon.

Either way, a lesson learned (good and bad) and that is really the point of this project.

Since I only have one working foot drive at the moment, I had to postpone testing the RC Control with channel mixing until I have received my replacement controller.

Not to be deterred I continued on!

Since I am planning to control the dome through Radio Control, I first needed to set the DIP Switch pins as illustrated here so it correctly handles the signal from our RC Receiver.

The Dome Drive is a single motor system, so the the wiring is quite straight forward. Using the diagram here, I connected the controller, motor and RC receiver together and after several redundant checks connected the 12V to the Syren 10 and 5V to the RC Receiver….and Zaaa….nope it worked fine. The RC Receiver blinked once and the Syren 10’s blue indicator LED came on as they both should.

Once I turned on the RC Transmitter, the RC Receiver’s Orange LED came on indicating it was receiving signal and I was able to successfully control the Dome Motors Rotation using the left and right motion of the DX6i’s Right Control Stick.

I had originally planned on using the Dimension Engineering Sabertooth 2×25 Motor Controller to run Artoo’s two foot drives because it gets high marks on the boards. However, Pololu offered a great deal on these 18v25 Motor Controllers on Cyber Monday so I figured I would give them a shot. I was able to get a pair of them for $85 versus the $130 of the Sabertooth, so time will tell if it was worth it or not.

Continue reading Prepping My Pololu Simple High-Power 18v25 Motor Controllers →

Now that we have decided to begin this project, I have spent some time reading the forums on Astromech.net , trying to learn as much as I can about the methods, processes and parts need to accomplish our Artoo build.

To keep our Artoo as realistic as possible, I am going to try to use as many aluminum or steel parts as possible, using resin or fiberglass parts only if others are not available. Continue reading Figuring it all Out! →

Dome Electronics Pt. 1: Building CuriousMarc’s Marcduino Dome Control System

Lighting Up the Dome, Part 1: Building the Teeces 3.2 Logic Display and PSI system.

Artoo’s First Steps: Testing His Differential Drive System via RC

Testing My Syren 10 and Pololu 18v25 Motor Controllers with Drive Motors…I went 2-3 with a Huge Strike Out!!

Configuring, Connecting (Binding) and Testing Artoo’s RC Transmitter and Receiver.

Tested.com interview (Senna's R2 Adventures)

Star Wars Day at the Corona Public Library 2015 (Victor's R2 Blog)

UPCOMING APPEARANCE: Oct 10, East Anaheim Branch Library (Senna's R2 Adventures)

Body work on BB (Thomas's R2 Blog)

R2LA XII (Victor's R2 Blog)

12th annual R2-LA (Senna's R2 Adventures)