Let's Make Robots!

Wall-e MkII - the tinkering begins...

As progress with Wall-e MkI (the test Wall-e) continues I can't help but start planning the 'proper' build, or the MkII :-)

Consider this a 'thinking-out-loud', rather than a definitive plan; I will document the second build in it's own Project.

Background

At the start of this project I bought two identical toys; the first was always meant to be for butchering, for hacking, for experimenting. The second was to be the finished artical. The first attempt has gone, and is continuing to go, much better than expected and has made it a lot further than anticipated! Isaac (my son, and client ha ha) has found Wall-e fascinating to watch and follow, even though arms and head movement or object avoidance has not been achieved.

MkI is currently in pieces being fixed (a motor has freed itself from it's gluey shackles to roam free inside Wall-e, the swine!).

While I am overjoyed at the progress both myself and Wall-e have made over the course of this project I think I have rethought the original build enough to start tentatively piecing together the much improved version...

The focus of this segment of redesigning is the internal 'block' of components; firming up the good things of the project, ironing out the bad things, and making it ready for future improvements.

Improvements

  • The Aduino Core - Uno to Nano

The MkI is based on an Arduino Uno with attached Adafruit motorshield. It is designed to run 4 motors and 2 servos, easy to use, has its own simple library etc, great to get started with.

My project, however, is evolving to require only 2 motors, yet 3 servos. For this application I feel the motorshield would be inefficient, taking too many pins to functions that aren't going to be used, and limiting my ability to expand.

The MkII will potentially be using an Arduino Nano, a L298n-based motor driver for the 2 motors and I will fashion my own Nano breakout perfboard to cater for servo, LED, sound and bluetooth connections etc. One day I may even attempt creating my own breakout board with my own integrated motor driver, but that is for when my pins are finalised and is a completely different project!

Advantages - smaller, better use of pins, more customisable options

Disadvantages - TBC

 

  • Motor gearing and Placement
 

When the MkI was being modded for motors the plan was to use normal, ungeared motors. These motors would be too chunky to fit nicely under Wall-e without being exposed, plus would need gearing to reduce speed/improve torque etc.

I then found some really small geared motors... This has resulted in geared gears ha ha, and while the torque is bordering on the monumental the speed is most certainly not.

The MkII plan is to mount these little motors underneath, going directly to the track wheel; if they don't fit in the area for them some PVC tubing will be used to cover them.

Advantages - better speed, more space inside Wall-e's body, less gearing=less things to go wrong!

Disadvantages - less torque, potential modding required to hide the arse-end of motors if they don't fit nicely

 

  • Power

The MkI is currently running from 2 paralleled 9V batteries, shoe-horned alongside the Uno. They do the job and last long enough, however aren't rechargable and require taking Wall-e apart to replace.

I bought 4 x 3.7v 5000mAh batteries to create a 14.4v pack - the plan was to couple that with a balanced recharging circuit pilfered from another device and stick it in instead. MkI doesn't have the space for the size of batteries however - insert sad face here.

MkII however, with its motor relocation and smaller internals, will have space under the Nano/motor driver combo. Hurrah!

One thing to factor in is the requirement of voltage regulators; one down to 12v for the motor driver, one down to 5v for the arduino. The motorshield had been regulating the power for the Arduino in MkI.

Advantages - long lasting, internal, rechargable, more than enough power to allow motors to run at optimal voltage,

Disadvantage - additional regulators required, recharging circuit to be considered

 

  • Arms/Head movement (FINALLY!!)

I have just received 4 servos to play with, and if my new, space-saving internal design allows, I'll be able to add the arm and head control i dreamed of at the beginning of this project. Hurrah!

 

 

  • Other bits and bobs 

Other things that i would like to do or need to sort out:

MicroUSB port on front/back of body; if possible connect to a hacked microUSB cable to the Arduino as well as to the recharging circuit. One can dream!

 

Feedback

I have attached a pic of the potential block taking shape - work will start soon on the breakout of the nano pins. Please comment if you have any tips or input :-)

Thanks for reading!

AttachmentSize
Idea1.14 MB
Sizing up on Wall-e base1.32 MB

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
Work on Wall-e MkII has been slow of late; a busy time with work and my Degree deadlines has restricted my tinkering time - sad face.

My last deadline is tomorrow; only 1500 words stand between me and moving the project forward!

Rather than use a breakout board for my Nano and use an external motor driver board, I have opted to create a board with inbuilt chips. I have ordered a L293 motor driver and an ATmega328p... Let the fun begin!

Today's experiments didnt go too well - uploaded a sketch to my nano to have a play with the servos, tweaked it, tried to re-upload it, and boom - avrdude error.

Shift-upload brings up an error - 

avrdude: usbdev_open(): did not find any USB device "usb"

Tomorrow I will look for a fix...

While I continue the process of procrastination regarding making a breakout board for my Nano I have decided to start working on the arduinoi coding.

I have an Uno-sized breakout board already for my Nano, so going to stick 3 servos and my motor driver on to that for now.

I'm just going to add some little motors and a 6v pack to the motor drive for now, just to work with.

I fear the 3 servos may be a bit to big to fit in close proximity in the shell. Not to worry though - i have a cheap microservo on order to play with. I will put this in place of the head servo, and if that's still to big i swap all three for the micro versions.

Nano, servo and motor testing

This is a list of my ins and outs required for my Nano, roughly broken up into groups for breakout board connection:

 

  • Bluetooth (4 pin female header)

BT Tx,BT Rx, 5v, GND (Data Pins:  )

  • Motor Driver (6 pin female header) 

Motor1+, Motor1-, Motor2+,Motor2-, 5v, GDN (Data Pins:  )

  • Original PCB Connections (6 pin female header)

LED Pin, GND, Sound1, Sound 2, 5v, GND (Data Pins: )

  • Servos (3 pin male headers, all sharing 5v and GND rails)

Servo1, Servo2, Servo3 (Data Pins: )

 

I will update my data pin lists soon :-)

 

watch it with 5v on the bluetooth module. Most of the bluetooth chips in use are 3.3v, some breakout boards then include level translation circuitry to enable them to function at 5v, some don't. Mine I have powered from 5v without issue http://www.amazon.co.uk/gp/product/B00EZJ3PM2/ref=oh_details_o03_s00_i00?ie=UTF8&psc=1  Although if you do blow it at 5v, pretty damn cheap to replace I guess.

Thanks for the info matey - I forgot to mention the bluetooth modules i tend to buy are the HC-06 ones on the breakout board :-)

I did my research before buying my first one for the first Wall-e, then ended up buying a second for toying with my Project number 2 (can't wait to crack on with that one!) and am ordering a third for Wall-e 2 -  wonderful little things, I must say!

Thanks for taking the time to have a look at my ramblings!

This is the base for the 2nd Wall-e, with the 4 batteries, Arduino Nano, future breakout board and Motor Driver in roughly the shape it has taken in my head.

Hopefully, with some slight modification to the inside of the shell, this design would allow comfortable mounting of servos for the arms and head just above.

Additionally this design, allows for the whole block to be assembled, taken apart and troubleshooted a lot easier than the wirey mess that is the first Wall-e's innards!

I am working on the requirements of my breakout board as we speak!