MAW-1 Mouse Droid

[kresty]

I found the instructions we'd created for the MAW-6 Droid:

MAW-6
Lego Mouse Droid

Operation

• Move gently!  This heavy prop replica and is more fragile and less agile than a normal R/C car.
  
• Turn the wheel to go left or right.
  
• Pull trigger to go forward.
  
• Push trigger to go back.
  
• Press lower side button to play random mouse droid sound FX.  Push upper button to stop after last sound ends.
  
• Press lower side button again to play Darth Vader theme after last sound stops.  Push upper button to stop music immediately.
  
• Push upper side button twice to stop all sounds (waits for last mouse FX to end)
  

Turning On

• Remove one side of droid.
  
• Install speaker and secure with Velcro.
  
• Plug audio jack into speaker.
  
• Turn on speaker.
  
• Increase volume to max if needed.
  
• Ensure audio control R/C cable is still connected with matching colors.
  
• Turn on transmitter, red light should light.
      If not, change transmitter batteries.
  
• Install battery and secure with Velcro.
  
• Plug in battery.  It will beep, LED will light and music will play.
      To stop the music press the lower side button on the transmitter a couple times, then the upper button.
  
• Replace droid side.
  

Turning Off

• Remove side of droid.
  
• Unplug battery.
  
• Turn off speaker.
  
• If storing, remove and charge speaker and battery.
  

Charging
Charger can be set to 1A or 2A.  1A takes longer but might make battery last longer.  2A should be able to charge the battery in about 90 minutes.

• Choose 1A or 2A.  1A is preferred if you are storing.
  
• Plug battery into charger and charger into wall.  Red LED goes on.  Green when charged.
  
• Plug speaker into USB cord, battery should light.  Goes off when charged.
  
• Remove 4 AAA batteries from transmitter and charge.  This does not need done every time, keep a charged set of spares as needed.
  

Main Board

Reference
This document, photos, plans, and much of the other information used to construct this droid are on the USB stick.

R/C Frame
Your MAW-6 droid is basically an R/C car with a fancy shell and a little bit of electronics.  In the event of problems most any R/C shop should be able to help. The body and drivetrain are based on an Axial SCX-10.

This is a 4WD frame.  The stock differentials have been made into “open differentials.”  This means that the wheels on each axle are not locked to each other.  With the heavy body, that aids in turning and reduced tire wear since the droid will normally have all 4 wheels on the ground.

The rear differential’s gear has been slowed to help compensate for the smaller front tires.  Even so, the rear wheels try to go about 10% further than the front wheels.

The Lego body is very heavy, so the shocks have been blocked so they don’t collapse.

To add the Lego wheels, special hubs were printed and installed.  See the later section on those.

The included 8.4v batteries seem to be about perfect.  Nimh is safer than other battery types, but other batteries are available if needed.  “Normal” RC car batteries between 7.2V and 10V should work, check the connector types.  It is probably worth asking an RC store for expertise if they need replaced.

Speaker
The speaker is a common Bluetooth speaker with AUX input.  It could be replaced with a different speaker if needed. 

Though intended to play the sound effects from the AUX cable, it is a Bluetooth speaker.  You could pair it to a phone and play sounds from the phone.

Additionally, the speaker has a slot for a micro SD card.  Sounds could be copied to that card and played from there, though the driver would not have any control of the playback then.

Electronics
MAW-6 is mostly a normal R/C car, however mouse droids play sounds, like when Wookies startle them!  Though a simple Bluetooth speaker amplifies the sounds, we need a way to play the sound files and switch them from the R/C transmitter.

The parts for the sound circuit are:

• A 5V regulator so that the 6V power from the battery doesn’t blow up the other chips.
  
• Two Pololu 2801 RC Switches With Digital Output that listen for the R/C channel 3 signal and send a signal when the side buttons on the transmitter are pressed.
  
• An Adafruit 2342 Sound FX Mini Sound Board OGG Trigger.  When the 2 lines from the switches are pulled low, this plays a random sound effect, or the Darth Vader theme song.
  

Instructions for the Pololu and Adafruit devices are on the USB stick, but they can be very difficult to configure and I wouldn’t recommend adjusting them.

The 3 wire R/C cable goes to the little board (make sure that black, red & white are aligned!)  From that, power goes to the 5V regulator, which then powers the 3 other boards.

Meanwhile, the white signal wire gets routed to both of the RC Switches.  Those are programmed so that one turns on slightly before the other one.  The transmitter is programmed to send different signals from the third channel switches on the side.

When the RC Switches “turn on”, they send their signal to a wire on the sound board.   The Darth Vader song is 0 and overrides the sound effects signal, which is 1.  The sound board then plays the tracks it was programmed to do and sends the sound to the speaker!

The sound board can be connected to a computer to change the files on it.  They have to be in OGG format, and the original files are on the USB stick.  I would recommend that if you want to play around with different sounds, probably try pairing a phone to the Bluetooth and don’t change the sound board programming.

WARNING:  The R/C Switches and transmitter are programmed to be in-sync.  Please don’t adjust their programming or they may be very difficult to get them to work again.  The switches would need to be unsoldered.

Lego
The body of the car is normal Lego.  Much of it has been glued with nasty solvents to keep it together as an R/C car.  It can be repaired as normal Lego, though if something actually breaks glue may be required.  Superglue sort of works, but not necessarily very well, so try to avoid driving it into a brick wall! ?

3D Printed Parts
Many parts are printed in ABS (the kind of plastic Lego is made from) on a 3D printer.  These are primarily to improve the structural support for the angles and to provide better access for the sides.  A few examples are in the kit. Files for most of these are on the USB stick.

Wheels
The wheels are a bit complicated.  Hopefully they won’t need removed, but it is possible the R/C car will need maintenance that requires their removal.  The Lego wheels & tires are normal Lego, so we filled them with 3D printed rubber to keep them from collapsing.



Wheel Hubs
The rear wheels have a 3D printed “hub” that attaches to the R/C car shaft with a normal locknut.  On top of that we’ve added an optional 3D printed spacer to help ensure the locknut doesn’t loosen.  The flats of the spacer have to match the nut, if there is difficulty, that could be omitted.

When removing the rear wheels, there’s a funny printed part with posts that can be used to press

The front wheels also have a printed hub that is attached normally.  It has a smaller optional spacer without the triangular lock.

Attaching Wheels to Hubs
Once the hubs are attached, the wheels are placed on the hubs, with a triangular washer on each wheel.  Those are then bolted  with 3 bolts to hold the wheels to the hubs.  The front wheels have little clearance and the Lego wheel will need to be screwed onto the shaft (after the hub is in place).

The hubcap is attached last.  The shaft is glued to the cap part, but it could break, so be careful.  It can be difficult to remove.  Try to gently pull both sides of the hubcap at the same time.

Attaching and Removing Side Panels
The side panels have a holder on their bottom and a magnetic catch on the top.  Slide the bottom down onto the holder, then lean the top in to the catches.  The top may be a bit tight.

To remove, peel away the top and then lift up.

  

     
Bottom “Skirt” pieces
The “skirt” parts only fit in one direction and have “keyed” bricks on the top to help align them.  The front and rear can exchange places, though the rear has the autographs on it right now.  Peel gently to remove and press carefully to install.

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Attachment of body to car frame
To get the body onto the frame, you will have to remove one or both of the end skirt pieces on the bottom of the droid body.  Be careful with the autographed bricks.

Lift the body over the frame and use the alignment bricks to fit one side and then the other side.  Note that the fit is pretty tight and it will probably take some work to get them aligned and seated properly.

Make sure none of the wires or Velcro are being pinched.

Once aligned, press the Lego into place.

Removal is the opposite.  The pads where they attach to each other are glued, so the bricks should only separate in one place.