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Modular Autonomous Robot Platform

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Sorry for my delayed response...
I've just make time to document my project on the official Raspberry Pi forum, but only in Spanish for now...
Hope google translator helps anyway:
https://translate.google.com.ar/ ... t-text=&act=url
My robot doesn't use any Arduino, but I believe yours will behave much better thanks to wheel encoders and will have better autonomy by using lipo battery.
Although mine just needed one ultrasonic sensor by implementing servo motor for sweeping movement
Keep the good work!

Edited by Tido at Apr 02, 2016 09:55

The construction phase is nearly over. I started out by making an effort to reduce motor noise. Motor induced noise is an issue with these systems as it can be a major contributor to system instability, or, said another way: "Why the heck is it doing that?" The task involves adding three capacitors;  one directly across the terminals and the other two attached from each terminal to ground.  Here, ground is attached to the motor case to help contain the noise.  

Motor noise filtering

Motor noise filtering

One of the other things I did is use twisted pair wiring to further help reduce noise induced unwanted effects.  You can see this much better in photo below.  I did this not only on the motors, but on the opto speed detectors and on the i2c interface connections you'll see later

Smoke Test #1

Smoke Test #1

This photo also shows the first smoke test.  Well actually, this is the second as you can see the led's are actually on.  The first smoke test was a real smoker as I accedently reversed the polarity of the battery connections on the motor shield.  Not good.  I'm probably going to have to replace  the LM293D drivers.  Possibly even the 595 chip.  Thank goodness they're on sockets.  ALWAYS check your wiring before applying power!

As you can see from the photo above, there's not a whole lot of room left on the platform.  That's where the makerbeam was useful. Here I built a frame to elevate a platform for the remaining modules and provided some room below where the battery will rest.  Here's a side view of that assembly.  The frame can be loosened and shifted back and forth while the top platform can be somewhat shifted side-to-side.

Side View

Side View

Here's a top view of the platform with the Lemaker guitar, the I2C level shifter (look closely in the center), and the controller for the ultrasonic transducers.  

There's only one thing left to do before we get to programming:  I need to mount the transducers and connect them to the controller.  I'm hoping to be able to finish that by tomorrow.

At this point, I'm concerned about the physical stability of the unit.  The front wheel is too close to the rear wheels and is just barely forward of center of the top platform.  I may have to shift the frame to the rear a bit and/or move the fromt wheel forwad where it might get mounted to the frame.  

Another concern is weight.  Although the frame is rather light, the plexiglass platform wiring, battery, and all the modules add up to a considerable amount.  Time will tell if the tmotors are up to the task.

That's all for now. I'm hopeful the next update on this project will include my first findings on the interaction between the modules.

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