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Friday, February 7, 2014

46. Robotics with PiBot. I - Assembling the PiBot

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This is intended to be the first in a set of posts called Robotics with PiBot.  I have no idea how many of these posts there will be, or even if this one is the last, should I blow the whole thing up as soon as I switch it on, making it the end of everything!

The PiBot is a kit for a 2-wheels-at-the-front, one-ball-bearing-behind robot (a tri-bot?), with the Raspberry Pi as its brain.  The kit can be purchased from Team PiBot at, where all the current details about the PiBot can be found.  

This is, of course, open source hardware and software, and I get the feeling it will be a long-term project.  Included with the pieces for assembly of the structure of the PiBot is a Bot Board, which allows the PiBot's systems to interact with the Raspberry Pi (which is not supplied).

Hopefully, it will look something like this when it's finished:
The kit currently consists of a chassis, the Bot Board interface, mentioned above, an audio capability (there's a speaker - that round object at the front), independent left and right motors with gearing assemblies, a PiCam control system (on the long arm at the top, Raspberry Pi Camera not supplied) consisting of a stepper motor and a servo (so that's why I was doing all this stuff with motors!), an 8 neo-pixel LED strip (the one illustrated above shows instead, a 16 neo-pixel ring surrounding the speaker), an ultrasound distance sensor (described as its 'eyes') and of course the potential to add almost anything you can imagine!

This post has no circuits, no code, only pictures - but watch this space!

Below are some pictures of the kit and its assembly:
Here are the 8 parts of the kit - straight out of the box, before assembly.
Part 1 before assembly - you can see the
speaker near the middle, and the red O-rings
used for holding the plastic pieces of the
chassis together.
Part 1 assembled
Part 2 before assembly.  The yellow items are
the left and right DC motors.
After assembling part 2
Part 3 before assembly.  The small red board is the audio module.
Part 3 assembled and mounted on the PiBot
- top view

Part 3 assembled and mounted on the PiBot
- there are some 'spare' parts
Part 3 has been assembled and mounted on
the other side of the PiBot.
Part 4 before assembly - 4 x AA battery holder
and ball bearing castor to act as a back wheel.
Part 4 - the battery holder (sans batteries) and the ball bearing mounted. Underside view.
So that's what the spare parts - perspex plate and 2 O-rings - are for! (a lid to stop the battery holder falling out).
Top view
Top view.  Note the on-off switch at the bottom left.
Underside view.  Contact with the ground
is at three points: each wheel, and the ball
bearing castor.
Underside view.
Top view
Top view
Part 5 - the interface board (Bot Board)
with 2 spare wires (I didn't need them).
Part 5 - underneath the Bot Board. Note the
small gel foot at the bottom right, to provide
a soft separation from the Pi's capacitor.
The Raspberry Pi (Model A) installed - it has to be a Rev 2 board with the mounting holes.  On the left you can see the SD card protruding from the Pi at the front of the PiBot: 
Top view - before the Bot Board (on the right)
has been attached to the Pi.
The audio plug has been connected.
Top view - the Bot Board has been mounted
on top of the Pi using the Pi's GPIO pins. 
I didn't use my Model B as it is a Rev 1 which doesn't have mounting holes. I'm not sure if the Model A will have enough USB sockets etc - I might have to buy yet another Raspberry Pi!
Top view - with some of the wiring connected.
Top view
The total weight at this stage, without batteries and camera assembly etc is 361g.  

I was advised to skip the pan and tilt parts, so I skipped Part 6 and 7 and went on to Part 8, the ultrasound transducer and neo-pixels:
Part 8. The ultrasound transducer (transmitter
and detector) - distance sensor (topside)
and LED strip (neo-pixels). My strip goes at the rear rather than at the front.
Part 8. The ultrasound transducer (underside) 
and the 
underside of the LED strip (neo-pixels)
Again there was only one place to mount the ultrasound transducer, so this is what the project looks like now:
From the front.  
From behind. This is the only place that
I could find to place the neo-pixels.
Note that the ultrasound transducer board is upside-down compared with the first picture above, showing how it should look when finished.

But what's this:
This is the voltage regulator, but at the moment I don't know where it goes.  One other thing - the wires go in the order Black, Orange, Red, and apparently they should be Black, Red, Orange, and may need to be corrected?

At this point I will pause while waiting for more details about what to do!!

To do:
Part 6. The stepper motor (to pan the PiCam)
Part 7. The servo (to tilt the PiCam)
Do come back later - there's lots more to come!

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