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Working Aliens Motion Tracker


That one has been on the back burner for a long time. Too long.
Long story short, I didn't have the ressources back then to get vintage parts for that prop. Well I now should ask JQ sabers (UK) if they could spot me a kango power drill to make another one (why not). Some of the parts are kinda hard to find now.
I got a Deck36 kit from spatcave on ebay. Cheap, like 60-70 USD from what I remember. Sounded like a good idea.

When I got the kit, some of it was nice, but some parts dislocated /  changed of shape, like if the PU resin was still floppy for a while. Or just an aged kit, parts pressing on each other in the storage box they were in, even if I'm sure spatcave stored it the proper way.

Some parts I saved with a hot air gun (on low temp) and a lighter, getting the plastic hot and reshaping the parts. Everything was going well. Then the upper body mess. That part I could never paint it. I think the problem is called resin weeping or sweating. Since PU resin is made of a sort of "oil", if you don't mix properly with extra care prior casting, you can have either some oil OR some catalyst not mixed properly and it will go out for ever. I tried hot water, bath of acetone, vinegar, primer, resin, bondo, nothing will stay. Not on all the surface, just on a few spot.

The project waited until chimera bespoke (UK) and I talked about his armor & blaster projects, and since he's a fantastic caster, he re casted the part for me, almost for free.
The issue is that the part was damaged a lot during all my attempts of covering it with various products. Anyhow the cast was NICE. So I started over.

The project won't be very "accurate" due to the kit format & no vintage part. I could still get a vivitar flash and the flash calculator card but I would prefer to save that for a screen accurate project if I ever make one. Still I have big plans for the electronics, to make FAR better than the MR version.

► December 2007....
The upper body mentioned above is the top part with the white/clear washer and the black rod inserted in it.
Sanding / bondo time...

[fast forward]
the new casted part. Needed some filler.

I plan to have working switches here and there, so I placed one in the hama remote

Testing the placement. I knew from here that there will be a naughty seam between the upper and lower body, I used some bondo to minimize this but still... That's due the the part wall which bended inward. I forgot to fix that prior molding / casting. Too late.

ahhhhh... my mobile bench and painting cabinet. Sorry to be pleased with myself. The air exhaust is so nice, no more paint stinking in the basement, vapors are taken out almost instantly. I let the fan on during the oven pre heat then I bake the primed parts at 45-50°C (not really baking and it's not Powder Coating, just a way to get the solvents out quicker and it hardens the paint).

Visible results. I didn't search for brown bess, I don't have an airbrush. But I spotted some spray cans of special automotive plastic paint. Supposed to be "grey" but at the end it's an interesting tint midway between grey and olive drab. Matching very well my M-40 ammo box I got from Tommin/ as well as my Pulse Rifle.

Making a battery pack with 2 x 16340. Stock protection PCBs were replaced by a dual one to make an actual 2 cell pack with a mid point to ensure cell balancing.

The recharge port is installed under the handle, where the AC cord was, very handy. I'll attach a small kill key with a piece of thin chain on the low strap hook.

Testing the future screen. That's the touch version for prototyping, the final thing won't need it of course.
Next is to start the electronics. I have many ideas. For now, collecting MT sounds. I'm not fully happy with what I have but I might just listen to the movie again, run some sonagram analysis to have the exact frequency behavior and sweep, and synthethize them again using max/msp.

Back in the day, I started a frame by frame work for a smaller screen. Not looking good I know. The new screen is 320x200 65k colors or something. It plays videos too.

My Motion tracker is equipped with a GPS and a compass (tilt compensated).

The goal is the next :
- the compass is controlling the orientation of the display which is rotating just like in the movie.
- the GPS is used to measure the distance to the alien fictive spot that was recorded and stored before

So, the interaction is kind of reversed since you're moving to the aliens and not the opposite but, still, it's very nice ! I initially though about building a RF beacon transmitting the actual position of the target to play hide and seek with my daughter but she's too young and the sad truth is that we kind of play alone with our expensive toys right ?

I was using a 5 Hz GPS head that fits perfectly in the motor area of the kango drill. The metal mesh isn't doing a faraday cage and the GPS signal is loud and clear.
For unknown reasons the GPS head died after some use (no change, switched the unit off, went back later, GPS dead), I ordered a new one and in the meanwhile, I had to hack an old one to keep working on the code.
I started by removing the RS 232 voltage level shifter chip and bridged them to get some 3.3V I/O to connect to my boards.

The GPS head I have now is too long, so I had to remove the front disc. Once I'll have my 5 Hz one, I'll be able to finalize the prop.

To avoid magnetic perturbations from the electronics and speaker (all in the hama slide viewer) I move the compass in the jobo lamp.

first test of the screen installed

I shielded a bit the speaker area

... and drilled some holes for the sound (another option was to put it in the body of the kango but it made more sense to me to have it close to the electronics

The MT has several "menus" to either operate or configure the unit. I'm using the rotary switch to select mode and menus.
In the lowest position of the rotary switch, the MT is idle, you get the rotating display but it's not beaming.
Position 2 : it beams and whistles if it finds the aliens, and displays the distance
Position 3 : the GPS menu, displays the current coordinates, the alien spot saved coordinates, and the compass and current angle of the aliens from your current location, which can be a "cheat mode" is you don't remember where to search. That's also where you can save a "way point", then current GPS location will be recorded as the alien spots. To record the way point, I use the hama remote release switch (functional).
Position 4 : system info menu, where you read the battery charge and voltage, and current interaction mode (further explained). I had fun with the sprites, when you enter the GPS menu, you get a "door" sliding right unveiling the GPS info screen. The blinkies are made of sprites too.

kudos to that guy who made the sci fi panels and textures. I only assembled them in a custom way but it's not my work.

Since I wanted to be able to play with the MT indoors (GPS won't work inside a house), I also integrated a motion sensor. It's hooked up so that even if left unattended, it's using it internal noise to simulation motion : you'll get the aliens coming to you even if you stay in place. And if you move, you accelerate the process.
When in inertial mode, the hama remote release switch is used to reset the alien distance and angle. The distance is within 20 and 28 meters so that it can be whether or not within the range of the screen, and the angle is computed to be within the field of "view" of the current orientation of the MT using the compass so that it's not a PITA to play with it.
I started by making real inertial calculation to measure the route taken by the user (works if made over a short term trip) but it makes the gameplay REALLY hard and not really "fun".

Current Limitations :

- I have to improve the data filtering on the compass. It's compensated but I sometimes get magnetic perturbations that make the display going crazy for a short time ("I AM READING RIIIIIGHT !!!!!"  :D). I'm currently using both linear and non linear filtering but I still have to adapt the filtering parameters to get it smooth enough and flicker free. Also, since the MT is held almost vertical, I might have to change the orientation of the compass to get straight readings.

- the GPS isn't just giving you a position, it's working on a navigation "fix" (solution). When you record the way point, even after staying still for a while, when you'll be walking to the alien spot the GPS will estimate your position based on your current speed and direction (course over ground). In general, unless you walk very slowly, you'll miss the spot by 1-2 meters.
I'm working down to 1/10000 of second of arc which is about 1.85 meter (theoretical resolution), however, in practice, at least with the GPS head I have, it's more like 2.5 to 4 meters. Still, it's working very well till you're at 4 meters of the target.

► video :

Final pictures !

As you'll see, despite the paint is a lighter  shade of olive drab compared to the PR (still, matching pretty well), it  can be seen as brown bess under certain lighting, which confirm what  happens in the movie (IIRC).
I apologize for the screen picture quality, quite hard to depict the exact look of it since it's behind the big lens.

I  added a slide show (currently 9 pictures) used as a screen saver. Not  much about saving energy but rather the OLED screen itself, to avoid  burning a static image (like what happens when you watch cartoon network  on a plasma TV).
I also reworked the power supply of the GPS, now I  don't need the kill key anymore, it's all controlled by the sliding  switch under the hama slide viewer, the recharge port is only used for  recharging.

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