Glowing Demon Eyes (That Blink!)




Introduction: Glowing Demon Eyes (That Blink!)

About: I like to make stuff. Drones and Tesla Coils. 3D printing too, oh yeah!

I created this prop 2 years ago; these photos had been waiting a while before they became the Instructable they were originally purposed for :)

My true inspiration for this decoration, came from the Pirates of the Caribbean ride at Disneyland. As you returned to the station (dock?) your boat was carried up a large conveyor belt, and in doing so, passed by a dark, dungeon-like crawlspace which contained several pairs of eerie-looking, red glowing eyes, which blinked randomly every few seconds or so. (It might not still be there though, I haven't been to D-land in years. I honestly wouldn't be surprised if they had replaced it with Queen Elsa in a lightsaber-duel with Darth Vader....)

First of all, many of the methods and materials I used can be substituted for other ones. However it's up to you to figure out any modifications, as I can only show my own example of how I did it.

I highly recommend that, before you read further in this Instructable, scroll all the way down to Step-6 to read my afterthoughts and reflection on this project.

Step 1: Gather Materials

You will need:

Foam-board (I used Elmer's. Its a bit sturdier than Dollar-tree foamboard, but either will work good)

Hobby-knife, with a fresh blade

Arduino (or use a Pi if you're a wizard) and its power supply

Breadboard, for testing and routing the wires neatly and easily.

colored LEDs

Resistors (I used 200 ohm resistors. You can use that or something very close to that value. I will explain how to choose the right resistor, further down)

Insulated copper wire, any kind. (I used magnet wire, as you can see in the photos)

Soldering stuff (Iron, Solder, Wet Sponge)

Hot glue

Glue-stick, or Adhesive-spray

A little box to enclose the arduino and keep it hidden out of sight.

24-hour timer, such as the "Intermatic TN311" for example.

free time

Things that you don't really need, but will make your life easier:

Multimeter (you should buy one, even if you don't build this project)

3D printer, with white filament (or access to one).

Regular 2D paper-printer, or access to one.

Various types of tape (Duct tape, Masking tape, Packaging-tape, are all useful for different things)

Computer, to read this Instructable (how are you even reading this without a computer?!?), and so you can listen to some sweet 80's music on youtube while you work.

Step 2: Arduino!

So the first thing you should do is to get the arduino set up and working. The reason for this is that the majority of people might be not-so-good with arduinos and their coding (like myself!) and in my opinion, it's always best to get the hardest things done first.

Lucky for you, I already have an arduino sketch for you to use! Of course, you are free and welcomed to edit it, and give it some style of your own!

The sketch is attached to this page. If you're already good with arduino-stuff, just get the sketch and you know what to do already, so DO IT. However, if you're new to arduino, and/or are buying an arduino for the first time in order to build this decoration, keep reading below:

You need the arduino IDE: Click on your operating system, listed in the turquoise box, to download the installer.

After you have the program installed, open the program from the directory which you installed it in. In the IDE, at the top click Tools. Look at "port:" and take note of what ports it lists.

Plug in your arduino through the USB port. Let windows do it's thing (your computer will auto install drivers).

In the IDE, at the top, click Tools. Look at the ports again now. The arduino is whichever port didn't appear the first time you checked. Make sure it's selected now.

Under Tools, make sure "Board:" is set to the correct board that you have.

Now you can finally open the sketch file that I made. Hit "Ctrl+O" and locate the sketch file and open it. Click the checkmark button to verify the sketch, then click the right-arrow button next to it, to upload the sketch to the arduino. Now your arduino is running the Loop!

It's a good Idea now to build a mock-up circuit on a breadboard to confirm that everything is working, and that you know how to wire the circuits.

In the photos here, I have two examples. One of them shows how each "channel" is connected to the board for the sketch I have uploaded (which is set-up for 6 pairs of eyes) but it only has a single LED and resistor on each channel.The other image shows only one channel connected, but it shows the proper wiring for two LEDs in parallel. That (in parallel) is how they will be wired up in the final steps, because you want one LED for each eye.

Let's talk about how to choose resistors.

The arduino will output a signal that is 5 Volts higher than ground, so that means positive 5 Volts relative to ground. That's the first important thing to know. Then you need a Datasheet for your LEDs; we want to know the current-limit rating of the LED; most are about 20 to 30 milliAmps, so we can try to limit our current to 20 mA, aka, 0.020 Ampere. You also need to know the voltage drop (aka, "Vf" forward voltage) across the diode. You can either measure this with a multimeter, or read it in the datasheet.

Let's pretend that our voltage drop across the diode is 2 Volts. When you apply 5 Volts to it, there is still 3V leftover to run rampant with current and blow up the LED! So we need to lower this voltage just a little more... by 3 volts exactly! So, we know how much current we want AND we know how much voltage is leftover to kill. This is where OHM'S LAW comes into play! V=I*R (Voltage=Current*Resistance). We know V and we know I, so just solve for R. So now that you algebra'd a little bit, we have V/I=R. 3/(0.02)= 150 Ohms.

That was just an example, but 200 Ohms will work for most LEDs. If you'd like to learn more in depth about selecting resistors for your LEDs, visit this tutorial:

Its important for me to mention, that it doesn't matter whether the resistor is in front or back of the LED, but the LED must be in the correct orientation for it to light up (because it's a diode). Of the two LED leads, there is a long leg, and a shorter leg. The long leg is the "+ side" which goes to the digital signal output. The shorter leg is the "- side" (ground) and goes to the ground pin of the arduino.

We will wire-up everything for real, in a later step.

Step 3: Print Those Prints, Multidimensionally!

So Now is a good time to 3D print the eyes. Use whatever settings that suit your printer best.

Click this Thingiverse link, and download whichever eyes you want, and print as many as you'd like!

If you don't have a 3D printer, you could just glue a piece of white paper, or plastic, glued to the back of the eye-holes, and then just use a sharpie to draw the pupils.

After you have the eyes, then you can "2D Print" the template for the foam-board boxes.

That is the PDF file that's attached. When selecting print settings, remember to select "actual size" and not "fit to page" or some other nonsense, because the image is 1:1 scale. If the scale is off, it might not work for regular-thickness foamboard (about 3/16ths of an inch).

Print as many as you want, then glue the paper to the foamboard with either a glue-stick or adhesive-spray, and give it some time to dry.

Step 4: Make the Foamboard Eye-Boxes, Add Eyes and LEDs, Then Seal It Up

Before you make any cuts, it is important to know where and how to make the cuts.

My inspiration for the box’s folding-design is drawn from the method used by Flite Test for their DIY foam-board RC airplanes. I learned so much about working with foam-board from Flite Test, I highly recommend watching one of their build videos. (This is a good one: watch the first few minutes, to see how he handles and glues the foamboard, because it’s the same method you’ll use here, but be aware the fold he makes is specifically an "A-fold")

If you have ever built a Flite Test airplane before, you may be familiar with the cuts and types of folds, A-folds and B-folds. However, most people are not familiar with those, so I will need to explain this very carefully.

Hopefully you can tell how to fold it from looking at my pictures, but here goes nothin’…

The lowercase “t” shape, is the part you will cut out from a larger piece of foamboard. That t-shape is made up of 6 separate rectangular sections, in-between each of which, there are 2 score-cuts that must be made. A score-cut is when you don’t cut all-the-way through the material. Essentially, you want to cut through the top paper-layer and into only a portion of the foam, but you MUST preserve the bottom layer of paper. Each of the 2 score-cuts divides the foam, so that when you bend the joint like a hinge, it will release a long, skinny strip of foamboard. You need to remove the long strips of foam from between the edges of all the rectangles, by bending each joint back, and wiggling the strip out until it’s free (The video I linked shows how to do that). Those skinny strips you remove, correspond to the cross-hatched pattern in the PDF template.

Before we move on from here, go ahead and use the 3D-printed eyes as a template to cut out the holes that they’ll be fitting in to. Just hold the eye flat down to the foamboard, and trace around the eye with a very sharp pencil. Then, use your hobby knife to cut out this shape, very carefully. It’s better to cut slightly inside the lines rather than outside the lines. Then go ahead and give the eyes a test-fit if you’d like, but don’t glue them in yet.

The central rectangular section of foamboard, the face where the eyes go through, I will refer to as the "centerpiece". The upper and lower rectangles (the same size as the centerpiece) I will call them "roof and floor" for reference. Take the foamboard “t” shape and lay it onto a flat surface such as a tabletop. Keeping the centerpiece flat against the table, you’re going to fold up the roof and floor, so that their inner-edges of paper are beside the foam edges of the centerpiece. The roof and floor foam edges should be flat against the bottom-layer of paper, and firmly pressed against the table. This is called a B-fold; ‘B’ stands for “beside”.

The sides, the two square pieces on either side of the centerpiece, will be folded up next. Notice how the sides fit perfectly between the roof and floor pieces. When the sides fold up, they will be above of the centerpiece, and their bottom foam-edges will be in contact with the top layer of paper of the centerpiece. This is called an A-fold. ‘A’ stands for “above”.

Make sure you practice and familiarize yourself with these folds BEFORE you put any hot-glue in the joints.

When you’re finally confident that you know how to make the fold, then, put a bead of hot glue along the entire length of the edge and make the fold, while remaining diligent to ensure that you hold it at exactly a 90-degree angle. Glue no more than 2 edges at a time to ensure that everything is staying nice and perpendicular. Keep holding it for at least 10-15 seconds to ensure it cools enough before you let go.

After those 4 sides are glued, you’re left with a nice hinged-door that fits perfectly on the back. Don’t glue this door down yet.

Insert the eyes into the holes, to where they are nearly flush, but just sticking out a little bit. On the inside of the box, place a hearty amount of hot glue around the perimeter of the eyes to fully secure them and seal up any gaps that may exist. Give it several minutes to fully cool down. You should then also apply a thin bead of hot glue around the perimeter of the eyes on the front side of box as well.

Now that the eyes are done, we can move on to installing the LED lights inside the box.

You simply need to poke the LED leads through the foamboard door, directly behind the location of the eye. Once that is done, put some hot glue around the LED bulbs to secure them in place. Add some reinforcement hot-glue along the inner edges of the foamboard, and now, you can finally seal the door shut with some hot glue around every edge and joint of the box. This will add a lot of strength to the box, and will aid in its resistance to weathering.

Get your soldering-stuff ready. Solder one resistor to each LED. Then solder the free-ends of the resistors together, and solder the the remaining LED leads together. Make sure that LEDs are facing the same way, so that you are soldering the same leads together; i.e., negative with negative, and positive with positive. Use the photos for reference.

Then, you should solder some short wires to the leads here, so that when you're making the full-length wire connections out in the yard, you only need to connect wire-to-wire. If you're using magnet-wire like I am, then you must use sandpaper, or a knife to scrape-off the insulation at the ends of the wire, before you can solder it.

You can then seal-up the exposed solder connections and resistors on the back of the box, using hot-glue.

To fully waterproof the box, fully wrap the box in either packaging-tape, or duct tape. If you use duct tape, you will need to cut around the eyes to expose them.

Step 5: Time to Go Outside...

Get some sort of enclosure box ready for the arduino to go inside of. I used a plastic ammo box that my brother threw in the trash. Make sure the arduino fits inside, alongside anything else you may have with the arduino. Inside my box, I also included a mini-breadboard, and I also made a common-ground rail because the mini-breadboard did not have power-rails. The power-supply cable for the arduino enters the box through a hole I made in the side. The wires for all of the eyes just enter the box through the top, and I simply just left the lid open slightly. Place the arduino box somewhere that it can stay dry, but you also want it as close to the eyes as possible.

Put some thought into where you want to place the eyes in your yard. You'll want a nice and dark place so that trick-or-treaters can't see that it's "just a box with eyes". My preference is for putting them in bushes.

When you know where you want them to go, secure them to a stem or branch of the foliage, with a zip-tie around the box, between the eyes.

This next part, I apologize, is slightly painstaking, but it shouldn't take too long.

We need to route the wires from the arduino, through the yard, to each set of eyes. Do this during the daytime, while the sun is still out.

1.) Start by taking one end of wire from your spool of wire, and tape it down securely, right next to the arduino-box, but make sure that you have plenty of slack for that wire to reach inside the arduino box to be plugged-in later. Once that end is secured, while holding the spool, carefully walk to the location of the eyes, letting the wire unspool as you move along. When you're at the eye-box, make sure the wire is not being pulled tight, and has plenty of slack leftover to move the wire around (so that you can neatly tuck-it under bushes and out of any walkways) then, snip the wire with enough length to be connected to the eye-box wires. Remove the wire insulation, and either solder them or twist them together to make the connection (I went with twisting them). You need to wrap some tape over the connection, so that it never comes into contact with the other wire's connection.

2.) For the other wire, make the wire-connection while you're still standing next to the eye-box, and carefully walk back to the arduino-box, allowing the wire to unspool as you move along. Make sure you keep the wires associated with each other, so that you can keep track of which pairs of wires are for which eyes. Once you've made it back to the arduino box, snip the wire, leaving enough slack to reach inside the box.

You can now test it out by plugging in the wires to the breadboard/arduino (remove the insulation first) and turning on the power to the arduino. Don't worry if you mix up the two wires, you can just reverse them if you don't see the eyes light up. Once you're satisfied that it is working, go ahead and repeat parts 1.) and 2.) for however many eye-boxes that you made.

Once all the eyes are wired-up in your yard, and you're plugging them into the breadboard, make sure that there's no exposed-wire (where you removed the insulation) that is touching other exposed wires.

If the wires need to pass over a walkway, use plenty of duct tape to tape the wire down against the floor, so that you remove the liability of people tripping over it. ;)

Plug the the arduino power supply into your wall-plug timer, and set the times that you want it to turn on and off at night.

That's it. Wait until night time, step back, and view the beautifully-frightening display which you have created!

Step 6: My Halloween Decoration Brings All the Boys to the Yard... (afterthoughts & Reflection)

In the end, there are a few things that I wish I had done differently. I might consider doing it differently this year, but I don't think i'll have enough time to fiddle with new ideas, and I'll most likely set it up again in the exact way you see it here; the way that I know works.

One thing that would have simplified my life, quite a bit, would have been to make the eye-boxes simultaneously house an arduino nano, and just have a single arduino nano inside each pair of eyes. That means I would only need to route a single power cable to each arduino, and no dealing with the mess of magnet wire.

Other considerations of mine include:

Adding actual connectors to the wires to make making-connections a breeze.

Using stranded-copper wires instead of solid-core magnet wire, to make the wires more flexible, and last longer.

Buying wire that is sold already spooled as a pair of wires, to reduce the amount of walking back-and-forth. I have considered using cat6 ethernet cabling; if you split open the outer jacket, you get 4 pairs of stranded wire, already twisted together.

Remember to use your ingenuity, to make up for my lack thereof! Discuss the ways that you did it differently in the comments!

This is my very first (published) Instructable. Hopefully I can edit it in case I find any mistakes later...

A big, well-deserved "Thank You!" goes to Autodesk, for hosting such a wonderful public space to share ideas and tutorials! I have been reading Instructables for years now, so it was about that time that I finally gave back.

Have a very happy (and spooky) Halloween!

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    2 years ago

    Looking for some help on the Arduino code. I'm very new to arduino and coding and have it all put together and it works great but I would like to slow down the frequency of the blinks. I want the speed of the blink to stay the same but Id just like them not to blink so often. Can someone explain what I need to change in the code for this? I would also like the "sleeping" one to keep it's eyes closed longer before opening and blinking. Any help is greatly appreciated. This is a great Instructable.


    Reply 2 years ago

    Thank you for liking my instructable!
    in the arduino sketch, all you really need to do is change the amounts of time in the delay() functions. If you notice, there are two delay functions per a monster's blink (and every blink is numbered with a comment, like //1 or //5.)
    The first delay is how long the eyes are closed for, and the second one is how much time passes until the next monster's blink occurs below it. (And remember they are in milliseconds, which are thousandths of a second.)
    So, if you want to space-out the blinks more (lower their frequency) then you only need to increase that second delay time in each numbered monster blink. For the "sleeper" that will be the fourth delay time instead.
    Doing this to all the monster's blinks, will lengthen the entire loop function (the whole cycle of the program) as well, and therefore it will naturally make the "sleeper" wake-up with lower frequency as well.
    Unfortunately, that's the only way I know that you'd be able to make him wake up less often, since the way I wrote this sketch is very "linear" and each blink's timing is dependent on the timing of all the other blinks... That is one downside for me, not knowing enough coding to make them all separate functions that run independently.
    If you look at the comments below, on person had a great idea to run each pair of eyes using a separate microcontroller called an ATtiny85, which would allow individual and independent adjustment of timing for each one. But it's probably too late for doing that, plus it's certainly more advanced of a technique. (Plus all those batteries you'd need to use!)
    Anyways, I hope this was enough explanation to get the idea of how to change what you wanted to change! If you have any other questions feel free to ask!
    Enjoy your Halloween!!!

    4 years ago

    Which color filament did you use to 3D print? Is it just a white or is it a more opaque color?


    Reply 4 years ago

    It's just white PLA, and opaque. Come to think of it, a natural-white PLA might look good too, because the natural white has a very very slight translucence to it. But if a clear filament is used, it may not completely diffuse (spread-out evenly) the light.


    4 years ago

    Hi Nabzim;

    Thanks for the idea, I liked because it's simple yet effective;

    I just realized an autonomous version of this (again, thanks for the idea): it works on 2 small 1,5V piles and the microcontroller is an ATtiny85 (the very-little brother of the Arduino, in some way), all this is small enough to be included in the box.

    I join a picture; the box is not finished yet, have to paint in white inside (I hope that this way the light, reflected, will be more uniformly diffused) and in black outside.

    I hope to have the time to build some others, to be scattered all around the garden. And to write an Instructable on it, too.

    The test in a month... :-)


    Reply 4 years ago

    Absolutely BEAUTIFUL!!! I'm so glad that my idea inspired yours, and thank you so much for posting it! :)
    You have proven that it's not necessary to use my complicated foamboard folding method, hopefully that will encourage more people to give it a shot!
    I actually have some ATtiny's but I hadn't thought of that! Great Idea!
    You might not need to paint the inside white, if you could fold up a piece of white paper so that it covers the back and sides, but honestly, the cardboard is already kind of white inside. Painting it black on the outside is a great idea too, but for mine this year, I bought some black colored duct tape on Amazon to wrap them in. (After two Halloweens of use, one of them started to give-way to the moisture, and fell apart as I was putting them away for the next year) so the duct tape hopefully will add the most waterproofing and extend the lifetime of the props.
    Again thanks for posting!


    Reply 4 years ago

    Good idea the white paper inside, much more easier than paint (and less expensive).

    Good also the dark tape outside, instead of painture: in fact the only need is to be somewhat rainproof, no need for good-looking details for an object that has to be hidden in a dark place...

    Once again, thanks for you Instructable!


    4 years ago on Step 6

    Great idea, but if you want to scatter the eyes around your garden the wires might get a bit long. Therefore I've come up with a simple 555 timer astable circuit that runs off a 9V battery (or almost any set of cells that give over about 4.5V). It only blinks 2 eyes at a time, but it's cheap and you can quickly make multiples.

    For a starting setup

    R1 = 1M

    R2 = 100K

    R3 = 330 (depends on Vcc)

    C1 = 4.7 uF

    C2 = 0.01 uF (any small value you have to hand will do, I used 0.022 uF)

    Vcc = 9V

    Adjust both R3s to give approximately 20 mA through each diode R3 = (Vcc - Vd) / 0.02 where Vc is the forward voltage drop of the LED, about 2.0V in the case of a red diode. Other currents are possible, the 555 can provide up to 100mA.

    R1, R2 and C1 give about 5 seconds with a 0.5 sec blink. To a first degree of approximation R2 adjusts the blink time, R1 the overall frequency along with C1.

    Alternatively you can put the two LEDs in series with a single resistor. R3 = (Vcc - 2Vd) / 0.02

    It is suggested in some quarters that C2 can be omitted and there is no need to connect pin 4 to Vcc, but both these risk possible instability.


    Reply 4 years ago

    Hi Peter, that's a good idea! Very simple, and still effective! I may attempt to incorporate both yours and Cotekino's ideas into my setup this year. I love any ideas that remove the work of stringing magnet-wire across my front yard! :)

    Kink Jarfold
    Kink Jarfold

    4 years ago on Step 6

    Eerily clever. So scary for Trick or Treaters. KJ

    Knox my socks off.png

    Reply 4 years ago

    Thank you! Maybe that's why we didn't get any trick or treaters last year... LOL!