spacer

Halloween 2011 - Mr Bubbles

See our 2012 Project: Viktor gets a Head Viktor gets a head  
See our 2010 Project: Dr. Who DALEK
Big Daddy    
This year my son and I decided to make a Big Daddy, 'Mr. Bubbles', from the game Bioshock. As usual, our building materials are cardboard from the local recycle bin plus a few rolls of Tuck Tape (the red tape used to join polyethylene vapour barriers), and a few cans of spray paint. In addition I've added an amplified PC speaker from the local e-waste dump, plus a few other electronic odds and ends.


 

YouTube Videos (more to come)  

 

A big compromise was needed to make this costume a reality. In videos where I've seen people wearing Big Daddy costumes, the wearers are virtually blind and require a full-time little sister to literally lead them around. As my son would need to be autonomous during his Safety Patrol Halloween party his costume needed to offer at least reasonable visibility. To this end I scaled down the Big Daddy so that my son's eyes stick out the top of the costume. So Big Daddy has shrunk to about 5' tall. I increased the size of the hump on the Big Daddy's back to hide the protruding top of my son's head.

Despite the shrink in size, the Big Daddy's bulk is still impressive and with a few extra effects will hopefully still inspire a few oohs and ahhs. Two things that we are doing to increase the wow factor are

  1. a working drill and
  2. Big Daddy moans and roars along with glowing eyes.

The mechanics are not very robust but should, I hope, survive the few days they are needed.

Update: OK, not as robust as I'd hoped. The original build was fine as long as the motor drove the drill. As soon as you started turning the drill by hand, the drive 'rubber band' would pop off the axil. I changed things a bit and it's a bit better now. Time will tell.

Coffee can forms foundation of drill

 

The drill started life as a metal coffee can (~4" diameter, 5.5" tall), a small ~1" diameter DC motor, two roller blade bearings from a previous project, an 8mm 1.25" bolt, some 5/8" MDF and a rubber band.

I cut an approximately 4" diameter disc out of 5/8" MDF. In the centre of this I drilled a 3/4" hole and then countersunk from each side a shallow 7/8" hole using flat-bottom Forstner bits. Roller blade bearings fit into these countersunk holes really nicely. An 8mm (or 5/16" if you can't get the metric) bolt and nut pinches the bearings together and provides a shaft onto which to mount the pulley and remaining disc.

The DC motor is slightly larger than 1" in diameter so I started with a 1" hole and then used my Dremel tool to enlarge the hole to fit. Afterwards the DC motor fit snuggly into the hole with a bit of persuasion.

Assembling the drillDrill Parts

I cut out a hole in the bottom of the coffee can so that the motor and bearing would fit once I attached the main disc onto the bottom of the can using three short screws.

I cut a pulley with an approximately 2.5" diameter. The disc needs to be profiled so that it peaks in the centre. Any belt will travel towards the highest spot and this should be in the centre. Finally I cut an approximately 4.5" diameter disc onto which the drill cone would mount. Both of these discs received a 5/16" hole in their centres which allowed them to thread firmly onto the bolt which forms the axil. A lightly stretched rubber band served as the pulley belt.

Assembled drill

Inside of Drill

Wearing Drill

A cardboard cylinder which projected backwards over the coffee can was mounted onto the largest disc and the drill cone was mounted onto it as seen above. I eventually added a drill thread using a cardboard spiral.

Inside the coffee can you can see a 'pistol grip' handle hot glued in place. This has an integrated trigger switch to turn the drill on and off. At the bottom you can see the voltage regulator board that controls the motor speed via a trim pot (under the board). The unit is powered by 4 AAA batteries.

The sound effects are played by a custom board I built for my PolyPod project that has been temporarily sidelined for Halloween. The leg controller board sports a dsPIC processor that contains a modest amount of program flash ram (128K) plus an audio DAC. The output of the DAC is fed through a disemboweled amplified PC speaker I found on the e-waste recycle dock.

Leg Controller becomes a Big Daddy controller

I sampled one Big Daddy moan and one roar. By resampling them to 8bit 3KHz signals I could squeeze these into the dsPIC without many contortions. By keeping the data under 32K I can insert the sound data into the dsPIC by defining some CONST arrays. In theory I could use a lot more flash ram for storage but to access it I'd have to directly access the program memory and I didn't have time to learn the ins and outs of that just right now.

Here's the code and project for Microchip's MPLab in case anyone is interested in seeing how I did things.

While a 3K sample rate doesn't sound like much, it's actually OK for two reasons. Big Daddies have low voices and secondly the audio DAC contributes a bit of magic of its own. The dsPIC audio DAC takes whatever signal you give it and over samples it by 256x. So the 3K rate becomes 768K. Of course the DAC can't put back in what's not there but it can sure make what's there sound a lot better than it normally would.

Finally the dsPIC board also controls some high intensity LEDs. When my son hits one button, the Big Daddy make a low keening moan and the green LED's turn on. When he hits the other button, the Big Daddy rages and the red LED's turn on. Control of the drill is via a button on a pistol grip within the drill unit.

Next Section: Building Big Daddy