The objective is to make a robot that can be controlled by any protester while sitting on a coffee, at their gardens or anywhere on their work by simply using a web page, where is possible to watch, hear and speak through any device. That’s why we created a self-balancing robot, with a rigid sturdy frame, a megaphone on the top as a symbol of protest and also as a way to talk to people.
What you gonna need:
1 × Smartphone with frontal camera
1 × Beaglebone black
2 × Matsushita GMX-6MP013A DC Motors
1 × 24V 6S LiPo battery
1 × Megaphone
1 × Wifi Bundle
2 × Cytron 13A, 5-25V Single DC Motor Controller
1 × Sabertooth 2X25A
2 × Voltage regulators
1 × MPU6050
1 × Battery Monitor
2 × Level Converter
1 × 100k resistor
1 × 6.8k resistor
1 × 820 resistor
1 × 8.2k resistor
3 × 150 resistor
1 × Optocoupler 4N35
1 × RGB Led
3 × 100nF Capacitors
2 × JST XH Connectors female/male (2 pins)
3 × JST XH Connectors female/male (3 pins)
1 × JST XH Connectors female/male (4 pins)
2 × JST XH Connectors female/male (5 pins)
0.528 m² × Plywood
2 m × L shape Aluminium
1 × Selfie Stick
2 × 18 tooth sprockets
2 × 45 tooth sprockets
40cm × #25 chain
4 × Locking bushes/collars
40 × M6x30cm bolts
24 × M6 washers
24 × M6 nuts
16 × Wing nuts
2 × Nylon spacers
2 × Buttons
4 × Bearings
62 cm × 12mm calibrated shaft
2 × Hinges
1 x Selfie Stick adapter
Step 1: The Body Pieces
So we decided to build the ProBot body using 12 mm plywood. First we marked the dimensions of the pieces and then we cut them with a circular saw. The dimensions are:
Middle sections: 10x40 mm
"Legs": 10x70 mm
Of course you can adapt dimensions, depending the size of the body that you want to build.
To hold the body pieces together, we cut with a band saw several aluminum L shape and then we made 4 holes with a 6 mm drill press to put the M6 bolts.
Step 2: Put the Body Pieces Together
After the cuts, we use M6x30 mm bolts, washers and M6 wingnuts to hold the L shape to the plywood. We use wingnuts to make the assembly/disassembly easier and faster. Then we can store the ProBot pieces on a suitcase and send to any part of the world xD
Step 3: Megaphone and Selfie Stick Supports
We made the megaphone support using the Autodesk Fusion 360 and the a CNC machine but you can use a jigsaw to cut the pieces. We assembled the pieces together on the top of the body with M6x30 mm bolts, washers and nuts. Between the support, we use 2 pieces of wood (65x125mm). To hold the megaphone to the wood support we use some bicycle wheel rubber with 2 wood screws on both sides.
For the selfie stick support, we made a small "top hat" adapter on a lathe and we lock it to the top of the body with 3 wood screws. To lock the selfie stick to the adapter we use a 3 mm grub screw.
Step 4: Bottom Box
To store all the electronics and to fix the wheels to the body, we made a box with metal plates on the sides. We made the sides plates using Autodesk Fusion 360 and a CNC Mini Mill. This sides plates allows to adjusts the motor position and change the chain tension.
We also made on the CNC the sprockets for the motor and the sprockets for the wheels. To lock the sprocket to the motor shaft we use a 3mm grub screw. Each wheel is composed with 3 new pieces, the sprocket the outside plate and the spacer, all this because the original bearing was really bad and we upgraded to better one's. The nylon spacer is used to keep the big sprocket away from the rubber and parallel to the outside holding plate. For the wheels shaft we choose a 12mm calibrated shaft and with 62 cm length and they were locked to the shaft with 1 locking bushe/collar, on each side.
To lock the top of the robot to the remaining box it was used 2 hinges. On this top, we made 2 holes, one for the buttons and another for LED that indicates the state of the ProBot. On the inside we keep Beaglebone Black microcontroller, with a custom pcb shield, the 24V 6S LiPo battery and all the electric installation. In order to organize all the components, we had to use 2 pieces of 4mm plywood to create some divisions, one for the battery and the other for the Beaglebone. The Beaglebone is inside of a aluminum box to avoid the electromagnetic noise produce by the motors,
Step 5: Electric Installion and Pcb Shield
On the box is all the electronics that we are using, protected from the outside conditions. We followed the electric diagram that is attached to this step. Is constituted by the battery, 2 pwm controllers, 2 voltage regulators and the Beaglebone. Here is the link to see how to hack the megaphone in order to connect a jack plug and send any sound to the megaphone.
On the pcb shield we have the MPU6050 sensor. With this sensor we can have the angle of the ProBot and then calculate the right reference. We also have on the pcb the inputs for the motors encoders to monitor their position, power supply for the Beaglebone, led that indicates the state of the ProBot, optocoupler for the battery monitor(with a buzzer), output for the pwm controllers our for the Sabertooth and resistor divider for monitoring the battery voltage. You can download here the pcb schematic.
Step 6: Software
The code that we are using is available on github also with the tutorial how to install on the Beaglebone and on the server. After the installation, you will be able to see the ProBots status (on-line or off-line) and, if you are the administrator, also launch the main routine on the Beaglebone from the webpage and see if someone is using one specific ProBot. After the login on the webpage, and if a ProBot is on-line and available, you can make a video call to the ProBot smartphone and control it! You can use keyboard keys, a gamepad or control it from a touch device!
Step 7: Protest!
Finally everything is ready! Now you can lunch your ProBot on anyplace! Here is the link for a youtube channel with some tests made with this ProBot version and with previous versions to.