Fast Traxx Rover: Beta

Add a Tyco Fast Traxx, WRT54G router, tons of batteries, web camera, gps head, and user control via a laptop. What do you have? A wicked homemade wireless tank-like rover!

While it may not look like the mid 90’s commercial boasting the original Fast Traxx, it has taken on a whole new dimension of geek-like excitement Übermodder has to offer, (batteries sold separately).

I have to give credit where it’s due, if it wasn’t for JBProjects this rover system would be a lot harder to implement. I will be using some their code and hardware to jump start our rover in the beta stages, then later revisions of the project will upgrade with our own code and programming structure. I might go as far as minor autonomy to help the rover navigate in tough situations, stay tuned…

Goals

I wanted to build a rover that was capable of:

• Trolling around in mildly rough terrain, like grass and gravel.
• Expanded battery life of greater than an hour.
• Sport a real time camera system with a gimbal to view objects that aren’t directly in front.
• Laptop control with an easy to use interface.
• Wireless radio that has large bandwidth capabilities and decent range (150 yards).
• Low cost, low power micro-controller system.
• GPS tracking device.

So you may ask yourself why? The better question is, why not? The experience learned from a systems integration standpoint is priceless. Also the obvious fact that robots are cool!

FastTraxx

Here we have a virgin Fast Traxx, perfect for what I need. It sports twin mubachi 370 motors, tank tracks, and lots of space to cram electronics into.

Chassis Mods

Here comes the worst part, chopping and cutting into the poor thing. Terrible huh? Choke up those childhood memories and get going. The first goal was to increase the number of 9.6V batteries stored within the chassis. The extra plastic parts were stripped to make way for the components that will be fitted on top and to make space for the electrical wiring. I did this by cutting the inside housing and bending the plastic with a heat gun.

After the modifications, the battery capacity was increased to three, two in the midsection and one underneath where the previous stock housing is located.

Drivetrain & Motor Controller

Seen in the picture above, the stock motor controller board was moved up front to clear up some space. The wires leading to the drive motors were lengthened to accommodate the modifications.

Motor Controller

Rather than starting from scratch and building a new motor controller board, why not use what was supplied in the first place? Here the stock controller board has been modified to accept signals from the proposed controlling system. The TAIYO 88-R IC chip that I soldered to only responds by setting the pin low via the controller board ground, see the pinout picture below. That way I can activate the motors to perform Forward Right/Left and Reverse Right/Left from the soldered control wires. I’ll be isolating the control wires from the controlling system by use of an opto-isolator because the ground potentials are different.

Also, be sure to disconnect the antenna and disable the antenna input filter circuit to keep out stray interference. I did this by removing the two capacitors at the input of the antenna. The antenna hole can be seen on the lower right side in the picture below.

Back of the Fast Traxx stock controller board

TAIYO 88-R IC pinout

Drivetrain

Since it was working well the drive system was left stock, other than some minor plastic weld epoxy repair work.

Camera

JBProjects found that the best network camera for this sorta setup was a Panisonic BL-C1A (detailed specs here). The nice things about about it is that it supports low voltage operation, hassle free setup/easy to use, and serves up a streaming url that is perfect to integrate into the basestation software. Just plug it into to the WRT54G router. I paid about $40 US for it on E-bay.

Specifications at-a-glance:

• Color Video
• Video Resolutions – 640 x 480, 320 x 240, 160 x 120
• JPEG image compression & video streaming
• Frame Rates (Max.) – 7.5 fps @ 640 x 480; 15 fps @ 320 x 240; 15 fps @ 160 x 120
• Motion Mode available
• 9VDC at 750 mA operation
• Green light indicator lets you know that you didn’t burn up the controller

(Courtesy, panasonic.com)

Basestation Control

I’ll be using a standard issue Dell laptop with a linksys 54g wireless card as a suitable basestation control center.

Software Interface

Ugh VB! Fine. I’ll use it for now. =)

Wireless Radio

WRT54G Router

Operating system

OpenWRT WhiteRussian v0.9 (Linux) for the WRT54G.

Sofware Contol

Hardware Interface

Rover Microcontroller

Hardware Inferface

(to wrt54g)

Safety features

Schematic & Circuit Board

GPS Tracking Device

GPS-500

Shown previously in the Budget USB Enabled GPS post, this tiny gps unit is perfect for tracking the location of the rover. The gps unit was connected in via the RS-232 chips on the rover microcontroller board and sent to the RX pin of serial port 0 (S0). For now, I was able to Cat the NMEA data output and show it on the screen in real-time.

Power Delivery

Power Consumption Estimations

Battery Packs

Linear Regulators

Camera’s 10V 750mah  linear regulator with three diodes to step down the voltage to around 9v.

Wireless router’s 12v 1.5A linear regulator.

Rover microcontroller 5v 750 mA linear regulator.

Schematic & Circuit Board

Testing, testing, tes..t..ing…

Breadboarding

Systems Integration

Smoke and broken mirrors

Mismatched grounds caused a small fire, I’m okay.

It works!

Making it all fit

For beta, just to proof-of-concept, I didn’t care much how it got there, just as long as it stayed. That’s when good ol’ masking tape came in handy.

Bear with us, this is a work-in-progress project. =)