WiFi RC Rat

That plush rat is so nice! What if we could control it from the phone? :D

Step 1: Choosing the Electronic Parts

To control it from the phone, we need:

- Bluetooth or WiFi module,

- microcontroller,

- 2 H bridges

- 2 motors

- battery

- Android phone or tablet

- RoboRemoFree app

Step 2: Choosing the WiFi Module

I chose the HUZZAH ESP8266 because:

- it has NodeMCU firmware and can run lua scripts, so we don't need an additional microcontroller

- it has at least 4 free GPIOs

- it can be powered from 3.5 to 16V

Step 3: Uploading Init.lua to ESP8266

The "init.lua" file contains the script that receives commands from WiFi and controls 4 GPIO pins that will be connected to H bridges. This file must be written to the ESP with filename "init.lua" so it will run at power on.

There are several ways to upload a file to ESP.

Here is how I do it (on Ubuntu Linux)

- Connect ESP to USB using an USB to Serial adapter (like FTDI)

- open CuteCom

- select device /dev/ttyUSB0 and baudrate 9600

- select LF line end and char delay 100ms

- click open device

- send some enters to make sure it is connected ok (it should answer with ">")

- open "luapaste.lua" with gedit and select all and copy

- paste in CuteCom and press enter and wait..............

- send the text "luapaste.lua"

- paste again the luapaste code

- now the ESP has "luapaste.lua" file, so next time you don't have to repeat these steps.

- close CuteCom

- open moserial Terminal

- select LF end

- click port setup and select select device /dev/ttyUSB0 and baudrate 9600 and uncheck handshakes

- click connect

- send some enters to make sure it is connected ok (it should answer with ">")

- send dofile("luapaste.lua")

- send the text init.lua

- paste the code from "init.lua" file

- send node.restart()

- it should answer something with "ESP8266 RC rat 1.0 powered by RoboRemo"

- close moserial Terminal

- disconnect the ESP

Step 4: Installing the RoboRemo Interface

Here is how to install the interface:

- install RoboRemoFree from Google Play

- copy the "rc rat.interface" file to the "roboremo" folder on the SD card

- open RoboRemoFree and choose menu -> interface -> import, and select the interface file

Step 5: Choosing the H Bridges, Motors and Wheels

The H bridges, motors and wheels should be small, so they can fit under the rat. Of course you can buy a dual H bridge, but it is much more fun to build it with SOT23 transistors (enjoy the videos). Building motors is not so easy, so I bought 2 Micro Metal Gearmotors (with gear ratio 30:1). I used 2 rubber stoppers as wheels.

Step 6: Connecting the Motors and Testing the H Bridges

Dual H bridge is alive and kicking :D

Step 7: Fixing All Together With Hotglue, Tape and Plastic Fasteners

Fixing all the electronics under the rat, and making some tests. The image shows how to connect the HUZZAH ESP to H Bridge. It is all powered by a LiPo cell. The foolproof diode is not the best solution, because it lowers the voltage to the ESP too (which already has one diode)

Step 8: The Rat in Action

Enjoy :)