Stargate Horus is done!

Got both of the fan mechanisms installed yesterday- really tricky to get them aligned properly. I also changed the way the head shell mounts to the head mechanism. I’ll shoot a build video this weekend that shows all of the movements and how it all works. After that it’s time for this bird to leave the nest and travel to its new home and get a proper paint job.


New Project- Asuna cosplay wings

I’ve been wanting to make a set of animatronic wings for some time so when I was asked to make these I pretty much jumped at the chance. This is a pretty challenging project for a couple of reasons. First, wings put a pretty big strain on servo motors so you need really powerful /durable servos and you need to make the wings very light weight. Second, there’s no room to mount any hardware! You can’t put the servos, batteries and controller board under the clothes and the mechanics are fairly complex as all four wings need to move up and down and flap forward and back. Everything has to fit behind the costumer’s back. You also need a hidden harness to support the wings. The trick with this project is not only to get everything to work properly but to make it look right. While there’s absolutely no way to make it look exactly like the pictures below I do believe it’s possible to get close enough and maintain the look of the character while still getting those awesome wings to move properly.

Stay tuned!


Fans are working!

Got the fans moving- woohoo! They move just like in the movie with the uppermost fan having the greatest movement and the bottom fan having the least movement. The servos have no trouble moving them, even at 4.8V (the servos are rated @7.4V) so no helper springs will be necessary.

Horus helmet fan mechanism

Here’s the nearly completed mechanism that makes the three fans move on each side of the head. Note that the schematic in the previous post shows the left side of the head and this is for the right side of the head. Still have a little bit of relief machining to do and drilling the fan blade mounting holes. After that I can attach the fan blades and power them up!

Stargate Horus head- making the fans move

In several scenes in the movie Stargate you can see how the fans on the sides of the Horus and Anubis helmets rotate in a progressive manner, with the upper fan moving the greatest amount and the lower fan moving the least. It’s a really cool effect and the set of three fans on either side of the helmet was made to move using a single servo. There’s not a lot space in that area of the helmet so it has to be a fairly compact mechanism.

In order to replicate this  I created a kinematic model of the mechanism using a free program from Autodesk called ForceEffect. This is a great bit of software that allows you to plot motions of all kinds of linkage mechanisms. I would have killed for software like this back in the day (20+ years ago) when designing suspension mountain bikes as I used to plot kinematics manually on paper. The fact that you can use an app like this on your phone or tablet is just awesome.

Unfortunately the photos I have of the original mechanics are not direct side shots and a fair bit of modification/extrapolation was required to get the proper range of movement, taking into account the necessary leverage ratios and clearances. The original helmet mechanics used helper springs to overcome the high leverage ratios- I have the benefit of modern digital servos that are much more powerful than the analog servos used when the film was made. The downside is that digital servos use more power and are noisy but that’s the price you have to pay…



Making the Horus eyes dim using radio control

I had a bit of trouble getting the eyes to dim properly. Yep- I let out the magic smoke. While getting ready to do a test with the radio transmitter I accidentally reversed the power wires to the FemtoBuck and smoked the driver chip. I ordered a replacement AL8805W5 chip, removed the blown one using a hot air tool and soldered the new one in. Note to self- ALWAYS use polarized connectors!

As soon as I was back in business I set about making the RC radio receiver signal work with the FemtoBuck. The FemtoBuck is able to dim the LEDs by applying a voltage range of .5V to 2.5V to its control pin. The problem is that my RC receiver doesn’t output a compatible signal so a fix is needed.

Arduino (Pro Mini) to the rescue! At the beginning of this project I thought I’d finally build something animatronic without an Arduino in it but the little bugger managed to work its way in there…

Using this code the Arduino was able to take the output of the receiver and turn it into something useful-

const int inputPinA = 2; // The pin connected to the RC receiver’s servo output A
const int outputPinA = 3; // Output PWM pin A

void setup() {
pinMode(inputPinA, INPUT);
void loop() {
unsigned long pulseLength;
pulseLength = constrain(pulseIn(inputPinA, HIGH), 1000, 3000);
analogWrite(outputPinA, map(pulseLength, 1000, 3000, 0, 255));

And with that I was able to get a full range dimmer for the eye LEDs using the RC transmitter.

Horus helmet eyes continued…

Finally getting back to work on this! Wired up the eyes last night and holy crap are they bright. They’re perfect.


My old variable power supply died so I quickly put one together using parts I salvaged from circuit boards in my scrap bin. For a power source I used an old power brick from a HP printer. At some point I’ll probably break down and buy a proper bench power supply…