ePiMP

Electric Powered Intelligent Multipurpose Platform

In short, the ePiMP is a low cost, open source wooden tank robot, that can be constructed by a single sheet of 12 mm plywood, two cheap battery powered drills and few 3d printed parts.

Changelog

• 2019-09-16: Version 1.1
  • Handles and holes to the backcover
  • Battery measurement circuit
  • Replaced wooden drive gears by plastic ones
  • 2 new mounting holes in the "lip" parts
• 2019-06-31: First version

Fabrication

Wooden pieces

All the pieces fit in a standard 2.44m by 1.2m sheet of plywood, 12 mm (15/32 in) thickness. The thickness can be changed but that would require changes in some internal slots that interlock, and some plastic pieces that assume 12 mm as the thickness.

The list of parts wooden parts to cut in the CNC is aprox. 112 total pieces (depending on the version of the design)

Already layout sheets (for X-Carve 1000mm or similar)

The layout use 790mm square sheets:

https://github.com/innovationgarage/epimp-body/blob/master/platform/svg/Workpiece%2038%20(ALL%20(unique)%20PIECES%20v1.1)/nested_optimized3.svg

Unique pieces

https://github.com/innovationgarage/epimp-body/blob/master/platform/svg/Workpiece%2038%20(ALL%20(unique)%20PIECES%20v1.1)/design.svg

The required quantity of the pieces is:

Plastic pieces

The list of needed printed parts is (56 total pieces, by the quantity specified in the filename): https://github.com/innovationgarage/epimp-body/tree/master/platform/stl

Assembly

You need the following parts and tools for the assembly:

• Wood glue
• Screwdrivers and wrenches
• 4x M8 long bolts (>10 cm) for the wheels
• 6x M8 inserts
• 2x M8 short bolts (>4 cm) for the back cover
• 2x M6 bolts and nut set for the clutch holder for the drills
• 2x cheap drills https://www.biltema.no/verktoy/el-verktoy/boremaskiner/drillskrutrekker-cd-12v-2000028475
• 8x skateboard ball bearings (608Z)
• 28x M6, 15 mm wood screws for the wheel center part that holds the bearings
• M5, 12 mm wood screws
• M8 washers

Wooden body

Tank tracks

The tank tracks require 64x 6mm thick by 40 mm length wooden dowels https://www.aliexpress.com/item/32908209214.html. Before cutting the link pieces, test the fit of your dowels to ensure the friction between the outer parts is enough to hold everything without glue.

Wheels and gears

The assembly is the following:

The wooden wheels go in between two bearing holders, using 3 of the M6 woodscrews per side. The two wheels on the back have the big gear in the interior side instead:

Drive and electric system

The brain is a ESP8266 that allows you to remote control the robot via Blynk and serial. The following parts are required:

• ESP8266 board, like a Wemos D1
• 2x 43A motor controller https://www.amazon.com/HiLetgo-BTS7960-Driver-Arduino-Current/dp/B00WSN98DC
• 5V DC-DC board (LM2596 or similar, depicted as 7805 in the circuit below)
• Thick wire (14AWG or lower)
• Screw terminals for joining wire
• Some wire, resistors, switch, heat shrink, etc

The resistor divider shown below is using 10K Ohm and 2.2K Ohm resistors for getting a value around 3V when the battery is fully charged.

Firmware

This is the firmware for the ESP8266: https://github.com/innovationgarage/epimp-body/tree/master/firmware/blynk_remote QR code for cloning the Blynk app:

Remember to create a new Auth code, and fill the credentials.h file with your own information. Check https://github.com/innovationgarage/epimp-body/blob/master/firmware/README.md for more details about the firmware.

Compile

For the compilation on Arduino you need the ESP8266 toolkit following: https://github.com/esp8266/Arduino#installing-with-boards-manager

Select "LOLIN(WEMOS) D1 R2 & Mini" from Tools/ Boards to compile.

Install the following libraries (Sketch/ Include library/ Manage):

• SimpleCLI
• Blynk