Building a Portal Turret With Motion Controlled Audio and Lighting




Introduction: Building a Portal Turret With Motion Controlled Audio and Lighting

About: I'm a 28 year old Nerd working as an animator in the game industry in Los Angeles. When I'm not in front of the computer you can usually find me building video game related props in my garage.

In this Instructable I'm going to show you how I went about building my very own life size talking Portal Turret from start to finish. This is a fairly in depth project that will cover every stage of construction and all the techniques I used along the way. Hopefully there will be a lot of information that you can pull out of this and use for all kinds of different projects.

For those that are unfamiliar with Portal, It is a fantastic puzzle game made by a studio called Valve that requires you to use two portals to solve all kinds of different puzzles.  It is really a fantastic game.  The turret for which this instructable is about is one of only two characters you interact with in the entire game, the other being GLaDOS.  The central AI of the complex.  The Turrets are so adorably deadly that I had to have one of my own.  Since nobody makes them I had to build one myself.  A little bit more work but definitely worth the effort.  Lets get started.

Materials and Tools used are broken down for each section.

Step 1: To Scale Blueprints

The very first step in the project was deciding how big I wanted to make the turret. I got in touch with someone at Valve and they told me that the turrets in the game stand 58 inches tall. Due to the nature of the design, I decided that making one this size would be prohibitively problematic and very expensive. I decided a more reasonable height to undertake was about 36 inches. This also seemed like a great size to display it once it was finished. This way it wouldn't take up an enormous amount of space in my place.

I had a friend of mine, Tyler Garrison, who is a wiz with Illustrator whip me up a set of blueprints with a height of 38 inches to the top of the antennas.  I then printed them out to scale and pulled all the measurements I would need from them as I worked through the project.  My friend did an outstanding job adding in little extra details like the Aperture logo and other details on the blueprints.  These blueprints will also make a great poster to hang on the wall with the finished project.

Step 2: Making the Masters - Body

The most important thing about this project is keeping it as light as possible.  The best way to achieve this with the body and arm panels is to create molds and cast hollow pieces.  These durable shells will be perfect for the final turret.  The main body and arms will be hollow while all the pieces relating to the legs will be solid for strength.

With the size decided, The first step was building the framework for the body.  My personal material of choice is MDF (medium density fiberboard) which can be picked up at any hardware store in 2x4 foot and 4x8 foot sheets.  This stuff is great because it has no grain and can be cut and sanded smooth with relative ease.  The dimensions for this were pulled straight from the blueprints and after an afternoons worth of work, I had skeleton frame work that looked like the body of a turret.

The next step was to fill in the gaps with styrofoam.  I cut down and shaped the roughly 10 pieces to fit into there respective slots leaving about 1/8 inch for the material it would be covered with.  The styrofoam was then covered with one of my favorite materials.  Apoxie Sculpt   If you have never used this stuff, I highly recommend it.  It is a 2 part epoxy clay.  You mix equal parts A and B and have about 2-3 hours of working time.  You work it just like clay, even using water to smooth it out.  After 24 hours it is hard as a rock and can be sanded or carved.  I covered all of the curved surfaces of the body with an 1/8 sheet of clay and waited 24 hours for it to dry.

A day or 2 later after the clay was fully cured, I sanded the surface as smooth as I could get it with my hand sander.  The secret when trying to get a very smooth surface is patience.  I spent many many hours sanding and refining to get the surface curves just right.

Next up on the body was many many coats of primer with lots of sanding between each coat and spot putty to fill in any low spots that popped up. Slowly working my way to finer and finer grit sandpaper, I ended up with a glassy smooth finish. The final coat was wet sanding with 1000 grit and then the surface received a coat of wax.  Any wax will do.  I used turtle wax.

Body ready for its mold.

Materials used for this stage
MDF (medium density fiberboard)
wood glue
Apoxie Sculpt

Tools used for this stage
Band saw
belt sander
hand sander

Step 3: Making the Masters - Arm and Legs

While I was making the body I was also working on the arm. Since I will be making a mold of this, only one master arm is required and I'll then cast it twice for the left and right side. The arm was built using a similar method to the body. I started out with a foam base and attached wooden plates for the 2 flat portions on the inner top and bottom sections. The outer surface was just covered with lots of Bondo and sanded to achieve the curved surface I needed.

The inside of the arm was formed by creating a template of the arc and using it to form the Bondo while it was still malleable. The hold for the gun box was cut out with a Dremel.

The entire arm then went through the same process as the body, and was primed and sanded until it was glassy smooth and ready for molding.

The same general techniques were used for the remaining parts. The 4 leg pieces started as blocks of wood and were shaped appropriately the a belt sander and hand sander. I found carving these straight from wood was a much faster technique than starting from foam, coating them in resin, and refining the shapes.

I only made one long leg piece to be cast 3 times, with the front two legs cut to the shorter length. I also made a single gun box to be cast twice.

That covers all the main pieces I will need to make a full turret. By the time I had finished the body, arms, legs and gun box, I lost count of the number of cans of primer I had gone through. It was seriously a lot of primer.

By this point my garage now has a nice thick layer of dust on absolutely everything! I'm really looking forward to having to clean it all up at the end of this project.

Materials used for this stage
MDF (medium density fiberboard)
Apoxie Sculpt

Tools used for this stage
Band saw
belt sander
hand sander

Step 4: Making the Molds - Body

Most of the molding and casting materials I used for this came from Reynolds Advanced Materials.
They are a great resource with a ton of great information on how to use their products.  I spent a ton of time on there website going through all of the different materials and learning as much as I could.  I was also fortunate enough to have one of their brick and mortar stores right here in town where I live.  Their staff was also really helpful in helping me with any remaining questions I had.

Due to the size that these molds will need to be, I'll be using the hard shell mold technique.  This technique consists of an inner silicone liner covered with a hard exterior shell to help it maintain the proper shape.  There are a bunch of resources online for different techniques, if you interested in casting and mold making you should definitely check them out. I decided to go with Smooth-On Rebound 25 rubber for the molds with a Plasti-Paste shell.  Both of these are available at Reynolds in smaller trial sizes as well as a 1 gallon size. 

Since this mold will be split into two pieces, the first step was to create the division line for the first half of the mold. It actually worked out really nicely that a piece of foam core perfectly fits into the center groove of the body that exists as part of the design.  After adding some registration keys, you can use anything really, I used acorn nuts, and a clay dam around the perimeter, its time for rubber.  The clay damn will stop the rubber from just running right off the side of the foam core.

The silicone comes in two parts that you mix equal volumes of to activate.  It was applied in layers to build up the proper thickness.  A thin initial coat was applied over the whole surface to make sure there weren't any air bubbles in the mold.  After this coat started to set, I applied a thicker second coat.  After this coat started to set I added in registration keys for the hard shell mold.  This will ensure that the rubber always fits properly into the hard shell and that there isn't any distortion of the shape.  For the third and final coat of silicone, I added a few drops of Thi-Vex II silicone thickener to thicken up the rubber allowing me to apply a thicker coat.  The thickener stops the rubber from flowing down and settling in the low spots. 
After the rubber had fully cured which takes about 6 hours,  The next step was to apply the hard shell.  The first thing to do was to move the clay damn out about 1 inch to make room for a hard shell rim.  The Plasti-Paste works similarly to the rubber.  It comes in two parts that need to be mixed together.  The Plasti-Paste is applied in a single step.  There is no need to do layers like the silicone.  After a few hours this is fully cured.

Time to do the other half of the mold.  After removing the foam core, the second half is pretty much the same as the first so I'm not going to bother repeating the steps.  Once the two half were made, The last thing I did was to drill holes around the edge.  There are for bolts to close up the mold and make it easier to cast pieces.

Materials used for this stage
Foam core
acorn nuts
oil based clay
Smooth-on Rebound 25 silicone rubber
Thi-Vex II silicone thickener
Smooth-on Plati-Paste
Mold release agent

Step 5: Making the Molds - Arm Panel and Gun Box

This section is going to be much shorter since the arm uses the same exact techniques used on the main body.  The only big difference between this mold and the body is that the central seam of the arm is not flat.  I used a thick card stock for the curved part of the arm.  Everything else for the arm is the same.

Since the gun box is square the mold for this will be really simple to make.  I first made an MDF box about 1/4 inch bigger then the gun box and molded the outside of the gun box.  After this set, I flipped it over and poured rubber into the back of the gun box to create an inner mold.  By doing this I can cast a thin walled box so I still have room for the electronics that need to go inside it.

The last image shows where I cut out the holes necessary for the various electronic components to be installed.

Materials used for this stage
Foam core
Acorn nuts
oil based clay
Smooth-on Rebound 25 silicone rubber
Thi-Vex II silicone thickener
Smooth-on Plati-Paste
Mold release agent

Step 6: Making the Molds - Legs

On to the legs. Since all these pieces are much smaller, Using a block mold is going to be much quicker and easier to do. This will also use a minimal amount of extra rubber.

These are poured in halves like the body to create two pieces for each mold.  After cutting the foam core down to shape to make a box around each piece, I decided where I wanted the seam from the mold to be and used the oil based clay to set up the first half of the mold.  You can see the clay under the long leg piece.  Then its as simple as just pouring in the rubber until it covers the entire surface.  Once its cured, you flip it over, remove the clay and pour the other half.  It is important to use a mold release agent to prevent the two halves of the mold from sticking together.  I forgot to do this on one piece and had to cut the thing back apart with an exact o blade.

The holes you see in the picture of the open molds are spots for the connection point with the body and legs. From here on out, all the pieces that are created will be part of the final turret which is pretty exciting! Its time to start casting pieces.

Materials used for this stage
oil based clay
Smooth-on Rebound 25 silicone rubber
Mold release agent

Step 7: Casting: Body and Arms and Legs

I decided to use Smooth-Cast 300 to cast all the pieces. My original plan was to use this ultra white plastic as the final surface of the turret, with only some clear coat added for extra shine. After some test casts I determined that wasn't really going to work for a few reasons. More on that later. With weight being such an important issue, all pieces relating to the body will be hollow, and all leg pieces solid for extra strength and support. I'll talk about the body and arm first.

My goal with the hollow pieces was to create a shell that is roughly 1/8" thick. After doing a few tests with different ways to achieve this, I decided to slush cast each part of the mold separately and then merge the 2 halves to create a final cast. This helped to guarantee that there weren't any spots that were too thin.

By doing it this way I can add a little extra plastic wherever it might be needed. I built up the thickness in layer for each half of the mold.  I made sure to not let the plastic fully cure between each coat so the layers would stick together.  The inner surfaces are not the prettiest thing to look at but it gets the job done.  The arm and the body are both done in this way.

There is a step that isn't pictured but  is really important.  Before I merged the two halves of the body, I embedded a  solid block of wood in the bottom rear of the main body that got sealed in place with more liquid plastic. This way there is a nice solid block that I will be able to drill into to attach the legs. The rear seam was also reinforced with a much thicker layer of plastic for structural support.

The two halves of the body and arm molds were then closed up and the bolts were tightened on the molds.  Through a small hole in the middle of each piece I poured a few more cups of liquid plastic and spun each piece along the seam to marry the two halves together.  I now have a solid hollow cast for the body and arms.

Its definitely a little more work to do it this way, but the final pulls are lightweight and durable!

The legs were much quicker to cast since they are solid.  No slush casting required.  I just filled up the molds, let the plastic cure and then removed the finished pieces.  In all there were 11 pieces that got cast for a single turret.  On to painting.

Materials used for this stage
Smoothcast 300
Plastic cups
mixer sticks

Step 8: Painting

I didn't really do anything special here to paint these pieces.  I just used a lot of layers to build up the finish I wanted.  I started out putting down several coats of white primer to cover up all the bondo used to smooth of any problem spots in the casts.  After the surface was completely covered with white primer I went over the whole surface with fine sandpaper to smooth out any bumps or specs of dust that were on the surface.  I also checked the entire piece looking for any low spots I might have missed and filled them in.  After I was happy with the primer, it was onto the satin white.  Two coats was all that was needed to fully cover everything.

The final stage of paint was the most important and by far the most time consuming.  When all was said and done, each piece received 6 coats of clear lacquer.  Each coat was applied and allowed to dry.  After it was dry, I would check the surface to make sure no dust or fuzz got stuck anywhere.  You would be surprised how many tiny black particles showed up caught in the clear coats.  Any imperfections were sanded out with very fine sand paper.  Then the next coat was applied.  Your probably asking why I applied 6 coats of clear onto the turret and the answer is that I really wanted the shine to pop and for the clear coat to look as glossy as possible.  You'll notice in the pictures below that the final result was well worth the effort.

Materials used for this stage
Valspar White Primer
Valspar White Satin Spray Paint
Valspare clear Lacquer

Tools used for this stage
hand sander
various grades of sand paper

Step 9: Electronics

Now here is the fun part of the project! Essentially bringing the turret to life. There are a few main elements that I wanted to incorporate into the final turret.  First being the red LEDs for the eye. Simple enough. Second is a series of audio clips controlled by a motion sensor. Third, the ability to play the original Portal theme song.

For those interested I am choosing to leave out the functionality of playing the audio clips when the turret is picked up, as well as the related audio clips when the turret is knocked over. The reason is pretty simple. This guy is not being built to take the abuse of constant handling or being knocked over all the time. While the individual parts of the turret are fairly strong, the assembled turret will be somewhat fragile on those very thin spindly legs. For weight reasons I am also leaving out the ability for the arms to move around like they do in the game. All of the extra engineering required with components and servos would likely add a good bit of weight to the turret. It would be cool, but I'm going to stick with a static model. Same with functioning guns... it all comes back to the weight.

Alright! After hours doing research on Mouser and Sparkfun researching components, and much experimentation, This is the list of parks that I settled on. The main components include an arduino uno, mp3 trigger, power regulation board and an epir motion sensor. There are various other smaller components like switches, buttons, LEDs, resistors, the speaker, battery packs and wall jacks. At the bottom of this page are two links to places you can pick up all the materials I used.

The programming was all done in the Arduino environment. Since I would classify myself as a beginning programmer, there were portions of the code that I needed some serious help with.  I was able to get the basic functions working but needed help with some of the more complicated stuff.  I called on a work buddy of mine, Pedram Javidpour: professional scripter extraordinaire, to help me get this program up and running. I couldn't have finished it without his help!  The finished program is attached at the bottom of this page as well for you to look at, dissect, and/or use if you decided to build a turret..

After the program was finished I was ready to start installing all of the electronics into the turret. I decided to split up the components between the arm and the main body cavity. The arm would get the battery pack, wall jack, power selector, motion sensor, main power switch, and the button to play the theme song. There are images of it all installed below.

So electronics in the arm cover power and small components. The main guts of this guy are located within the body cavity. In the picture below you can see the arduino on the right side, the mp3 trigger on the bottom, and the speaker on the left. The cluster of wire at the top link up to the eye. These components were all just glued in place with standoffs.

Installing all of this stuff was definitely tricky.  The most important part is just to make sure that you connect up the right wires to the right places and test each component as you go.  It will not be fun it you get everything cleanly installed and it doesn't turn on.  You will then spend many hours trying to troubleshot where the problem is.

Materials used in this stage
gorilla glue

Tools used in this stage
Soldering iron
wire strippers
heat gun
shrink tubing

Step 10: Making the Eye

Looking into the soul of an armed and emotionless turret can be slightly hazardous to your health but I really wanted to go all out just in case someone was so inclined as to gaze into the eye of fate.

Taking the time to make sure it came out as good as possible was very important.  After finding a suitable plastic lens I could start on making all of the other necessary pieces. Here is an image of everything that makes up a finished eye. The black disks were designed and laser cut to create the groove pattern you see in the final eye. The translucent disk will help diffuse the red LEDs, and the black rod will create the dot in the center.

After roughly fitting all the pieces together I noticed that the light spill coming down the sides of the lens was really messing with the overall look of the eye. I resolved this issue by coating the inside of the lens with black electrical tape to prevent any light leak from happening. This way the only light you will see is coming through the translucent surface of the eye. The final result is perfect.

All that's left is to install the eye and connect up the power. With the electronics finished and installed, all that remains is the detail work.

Materials used for this stage
Skil Router bit cover from Lowes
2" protoboard
4 bright red LEDs
Custom Laser cut and engraved eye detail pieces from ponoko
translucent plastic sheet
Small piece of black plastic rob
black electrical tape

Laser Cutting done by

Step 11: Aluminum Leg Rods

These pieces were tricky to figure out how to make.  After doing some research, I finally settled on using 3/8 inch aluminum rods that you can pick up at any hardware store.  Getting the right curve is pretty important as it will effect the angle of the legs so I built two separate jigs that I used to bend the front and rear leg pieces.  Two for the front, one for the rear.  3/8 inch aluminum is thin enough that you can bend them by hand although it does take some effort.

The first thing I needed to do was build a template for each of the two leg shapes that I could use to bend the rods.  I built these out of 1/2 inch MDF and they reflect the shape of each piece.  I firmly clamped these to the edge of my work table and insert a 3/8 inch aluminum rod into the slot and then bent the rod to match the shape.  These rods then had the excess length trimmed off to set there final length.  All that is left to do is to give them a quick coat of black gloss spray paint and then attack them to the leg pieces.  All of these pieces were then epoxied together for maximum strength.

Materials used for this stage
MDF (medium density fiberboard)
3/8 inch aluminum rods
Black glossy spray paint
5 minute epoxie

Tools used for this stage
Band saw
Dremel with cutting blades

Step 12: Details

We're down to just the last dew detail pieces and the turret is finished.  First up will be the detail piping on the inside of the side body cavities.  These are 1/4 inch black Delrin rods I bought from Interstate Plastics.  Any plastic supplier will probably carry them.  I cut them down to the rough dimensions for each piece needed and then used a heat gun to bend the shapes.  To help the plastic set quicker, I dip the rod in cold water to cool the plastic.  I then created small styrene mounts for these.  They are the tiny white squares that the black rods go through.  I sanded the edges smooth and then cut down the excess Delrin.  In the second image below you'll see a few that have already been trimmed and a few that haven't.

The next detail piece is the gun barrels.  There are four in total.  Two longer and Two shorter.  I started with a hole saw and cut a bunch of circles out of MDF.  You can do this with just a band saw and a sander. 

The last detail piece is the 2 antennas. These are pretty straight forward in there construction.  I picked up some styrene piping from a local hobby store and used the same method as the Delrin to shape them.  A short time under the heat gun and they are easily bend to the desired shape.  A quick coat of silver spray paint and they're all finished

Materials used for this stage
Styrene sheet
Small Styrene rod
1/4 inch Delrin rod

Tools used for this stage
heat gun
band saw
belt sander
sand paper
Hole saw

Step 13: Finished Turret in Action

And that's it.  All that's left is to take some fancy pictures to show off the result of all this hard work.

Here is a short video of the final turret in action.

Make It Stick Contest 2

First Prize in the
Make It Stick Contest 2

4th Epilog Challenge

Second Prize in the
4th Epilog Challenge



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    181 Discussions

    I noticed that a lot of the sections have measurements with the exception of the curved leg portions and the white leg covers. Any chance you could share the dimensions for those?

    is this turret wireless

    This is so impressive, I really love it!

    Here I resized a version of the blueprint to print actualy size of the turret and increased the quality it isn't prefect but it pretty close to the original

    1 reply

    So, Would this be good for a Portal/Halo/Tf2/Borderlands/Half-Life Nerf war? Were having some debate over which Turret we should use. A tf2, or a Portal. So, Is it easy? And how long will it take to make?

    valve didnt actually make it, it was a gift to them

    Did anyone know that Valve has something like this at their HQ?

    No, not robots straight up murdering people.

    Valve isn't that evil.

    1 reply

    3 years ago

    Hello, is it possible to have access to the blueprints your friend did for you? I don't have tyler garrison as a friend... ? and i want to build a turret.

    Does anybody have a estimated Cost/Hours for this? I really don't wanna start this and run out of money halfway through or not have the time to finish the build.

    I would like that but just to make it sound more deadly... For Example went it said target acquired just in a deeper voice and no singing. Make it sound like it's a treat. Other than that it is pretty interesting.

    1 reply