Introduction: Four-Motor Laser Spirograph

About: I have a passion for tweaking things. Whether it be modding video game consoles, creating custom laser displays, or any creations with lights I love solving problems through unorthodox means. I like to go whe…
Bouncing a laser beam off a mirror rotating at any angle above 0 degrees will create the illusion of a circle to the human eye. Combine two rotating mirrors, and complex shapes begin to emerge. With every additional mirror, the perceived image becomes more complex and intricate, with the ability to create some very beautiful and bizarre flowing patterns of light.

Most laser spirographs consist of only two mirrors, limiting the complexity of their shapes for the sake of easy construction and bulky size. I have seen various guides on the net about three mirror spirographs, and after creating one figured I would up-the-ante: a four-motor spirograph in a compact box which is portable. This design will accept the use of any pen-style laser pointer, and through the use of potentiometers (variable resistors) to adjust the rotation speed of the mirrors, new shapes can be created. The benefit of using a laser beam allows the image to be projected to any size, on an indoor wall, an outdoor tree, through a lake/pool, snow, or the side of a building.

I hope you enjoy creating and sharing this display of light, which myself, friends, family, and strangers alike have been drawn to the limitless shapes created through exploiting human persistence-of-vision.

This is a rather complex mod. I'm already assuming you know how to solder, and have some basic understanding of wiring. Though you definitely could complete this mod as a first project, it will be rather confusing and challenging.

This violet projector made by user JoeMonkey from following this instructable -- Awesome job Joe!

Laser light while very enjoyable can be extremely dangerous, dangerous to the point that most people don't understand the numbers of how powerful 10 mW (milliwatts) is, much less 100 or 500. While many projects have unnecessary warning labels, the concentrated energy from a laser beam really can blind the eyes of those who look into it's beam. Realistically, any laser with a power over 10mW (3.84mW is the power at which human eyes begin to be damaged) shone directly into a persons eye will de-nature (boil/cook) the rods on the back of their retina. This becomes a big problem if a person looks directly at the beam, as their center of vision will be damaged, inhibiting reading and other fine viewing permanently. The damage comes because the lens of the eye focuses light so precisely, what was 10 mW ends up becoming 80mW since it's focused on such a small area of the retina. It sucks to have your vision ruined for life for a toy. That being said, the cheap crappy red laser pointers for $2 tend to output about 0.5mW, and won't ever hurt you.

Second, don't shine a laser at anyone who doesn't want one pointed at them. In multiple states pointing a laser beam at a person is equivalent to assault with a knife. Many people have an irrational fear (thanks to being portrayed inaccurately in movies and television) that a laser beam is associated with a firearm, as such ignorant people fearing for their life can earn you a trip to jail. This includes pointing laser beams through people's windows, their car, or even simply near them, people are fearful.

Third, never point a laser beam at any aircraft or helicopter. These vehicles often use polycarbonate for their window "glass", and a laser beam anywhere on the window will scatter through the entire surface making it impossible to see out. Pilots take laser beams very seriously, and the government crackdown in the United States is especially strong. I personally know a friend who has been given a $1,000+ ticket and criminal record for pointing a 5mW laser at a police helicopter. Though the real life danger for pilots is minimal and over-hyped, government over-reaction to laser beams is not.

Fourth, eye damage from lasers usually happens without a victim immediately recognizing anything ever happened. A single flash from a 100mW might make you flinch and say, "Wow, that was lucky". In reality, you just toasted a line across your retina, but other parts of your eyes will compensate your vision to the point you don't notice. With multiple exposures (though really, a single 200mW+ exposure will truly screw you up), eventually the damage will accumulate, things become blurry, and you can't read.

Now with all the scary stuff out of the way, let's get to building!

Step 1: Parts Listing

Power Drill (~$80 )- Any power drill will do, we are only going through plastic.

Drill Bits (Set of 20 bits: $20) - 1/16", 1/4", 1/8", 3/8", 1/2" drill bits were used in this mod.

Electrical Conduit Box (~$3, Lowes) - Gray box measuring 6" Width x 6" Length x 4" Height. Most are intended as a junction box for pipes that carry electric wires, the one I purchased doesn't have any holes for pipes.

Electrical Conduit Fitting (Pipe Adapter) (~$1, Lowes) - My laser is exactly 3/4" at its front, as such I purchased a 3/4" -> 1/2" fitting. This allows the laser to be inserted into the box without wobbling around, but prevents the laser from falling into the box. Get whatever size fits your laser, only the beam needs to pass through.

Rotary Rasp ($5) - The proper method for drilling a hole for the conduit fitting would be either a hole-saw, or an omni-bit. As an omni-bit costs $50, and I couldn't be sure of the proper hole-saw size to use (each hole saw costs about $10), this cheaper method will do.

On / Off Toggle Switches 4x ($8) - $2 each at Radioshack. A ripoff sure, but they are convenient.

Red Safety On/Off Switch 1x ($4) - The red knob that you see on fighter-pilot joysticks and nuclear briefcases in movies. Complete overkill for this mod, but it just looks so cool!

1.5v-3.0v Hobby DC Motors 4x ($8) - $2 each at Radioshack. You could purchase mini-motors (cell-phone vibrators usually), which have the benefit of higher rpms at a smaller size (but they are usually to long to fit inside a box this small), but less torque and a whole lot of noise.

100 Ohm Linear Potentiometers 1/2 Watt 4x ($6) - These restrict the amount of electricity that can go into the motors, making them go faster or slower. Purchase them online, which automatically adds $4 of shipping. They are impossible to find at any brick and mortar store for low ohm ratings. Most stores sell very high ohmage ratings, such as 1k, 5k, 50k, 100k, 1M, while we want 100. The 1/2 watt rating is strongly suggested, but the motors would likely run anyways with 1/4 watt max. In this guide I initially used 500 Ohm resistors, which turned out to be far too stiff, then I dropped down to 120ohm, and now I suggest 100ohm. By being too resistive, I mean that while the knob in turning from full on to full off may be about 240 degrees of rotation, only about a 30 degree window will adjust the speed, making it really "touchy".  I purchased mine from

Potentiometer Knobs 4x ($6) - I purchased these knobs from Radioshack. They are decorative knobs, compared to the black and white-lined knobs. Either style works the same. They stick on the turning post of a potentiometer, and a tiny screw in the side tightens down onto the post.

1 Laser Pointer (~$10-$infinity) - For this guide I am using a 150mW Rayfoss laser, which cost $100. Most people can't justify spending so much cash on a light, here are your options.

Laser Companies
- A respectable Chinese company, the first I recommend for newcomers. Rayfoss sells medium quality lasers for excellent prices. If you have any questions or concerns, e-mail them and expect amazing customer service. They bend over backwards to meet your order needs, and often throw in free goodies if you are friendly. A non-respectable Chinese company, but they sell low quality lasers for rock-bottom prices. The quality is still far higher than what you would find at a normal store like Target or Sharper Image. Only purchase the 5mW from here, as their 20mw and up lasers all look the same brightness (they are all the same laser, but they do a POT mod on them to boost the power, resulting in higher amounts of infrared light which helps fake the numbers, green light stays the same). - A very respectable American company. Expect high quality for matching prices. They sell unusual lenses and diffractors. - Laboratory and military level equipment, ultra-high quality, very high prices. They are excessively overpriced on the low-end (below 100mW), but if you want very high-powered lasers, they are tough to beat. - Medium quality company. The main product to purchase from them is their laser safety goggles, which are top quality for low price. They have an excellent list of lenses and optics to purchase as well. As any respectable laser enthusiast would say, you should buy goggles since $25 is a small price to save your vision. I personally don't use them unless I'm working with something high powered (over 300mW), and am very careful and aware of what I am reflecting off of, that being said, I'm still only a 1/100th of a second reflection off my eye to go blind. - Stay away from this company. With good marketing they take advantage of unknowledgable newbies by selling them low quality lasers and gear for insane prices. Don't be sucked in by their flashy videos and photos (which are very misrepresented by playing with photoshop), they also boost their public image by paying people to write extremely favorable reviews of their company. To put it simply, they're a ripoff.

Soldering Iron 15 Watt ($15) - Radioshack, it heats up to about 260 C (500 F) to melt solder.

.022" Silver Rosin Core Solder ($3) - I prefer rosin core as it helps make cleaner welds with minimal effort. Again, available at Radioshack.

Needle-nose Pliers ($5) - Your second most important tool, next to the soldering iron.

18-22 AWG (Gauge) Wire ($3) - The raw wire used to conduct electricity between different parts of the spirograph. Any wire will work, but I find 18 AWG is the easiest to handle. Get a few different colors if you can, I use red, yellow, and black in this mod.

Electrical Tape ($2) - Used to wrap up exposed connections to prevent short-circuits.

Hot Glue Gun ($8) or BIC Lighter ($2) - To melt hot glue. After leaving my hot glue gun on for four hours straight, it exploded and blew the breaker. Now I use a BIC lighter.

Hot Glue Sticks ($4) - This glue will fix the motors in alignment for the laser beam, as well as hold on the external plastic laser mount and window.

Knife ($4) or Wire Strippers ($8) - To remove plastic sheathing from wires. I personally prefer the knife due to being able to remove sheathing which the strippers can't reach in tight spaces.

K'nex / Lego Lifters ($Peanuts) - Use anything 1cm (1/4") tall. These are just hard blocks that lift the mirrors up a bit to not scrape against the case.

2 AA Battery Pack & 9 volt Connector ($5) - Radioshack again, if you can, purchase the battery pack with the pre-attached 9 volt snap on connector. They were sold out so I had to use bare wires to attach my own 9-volt connector

Plexiglass/Acrylic Glass (Optional) ($10/ 2'x4' sheet") - A window for where the laser exits. It's not necessary in any way, and to some extent causes your laser to scatter upon passing through it. I just put on the window to help minimize dust on the mirrors.

1" Diameter Acrylic Mirrors ($5 / 24 mirrors) - I purchased these at the craft store Michaels. I personally chemical treated these mirrors to transform them into "front surface mirrors", meaning there is no protective acrylic layer over the reflective aluminum, but rather the metal is exposed (and extremely easy to scratch) for a perfect reflection.

Sidenote on chemical treating: Purchasing an equivalent front surface mirror would cost $7-20 per 1" mirror. I went to my local automotive store, purchased Aircraft Stripper (chemically designed to not attack aluminum, but requires you to use chemical resistant gloves and be careful when breathing around the spray [brain damage]), to remove the protective gray backing from the mirrors and expose the aluminum. Even with chemical resistant gloves, it would burn through them every 10 minutes or so. This is a rather advanced step that is not necessary, but is highly encouraged to prevent laser scatter and is beyond the scope of this instructable. Google is your friend if you are interested. Process went: Spray stripper on gray adhesive, wait 10mins, wash in hot tap water, rinse with de-ionized water, dry with soft paper towel via pressing (no scrubbing); spray stripper on brown adhesive residue, wait 4 minutes, wash/rinse/dry; spray stripper on remaining residue, wait 2 minutes, wash/rinse/dry, done.

Step 2: Prepping Motors and Mirrors

Attaching the Mirrors to the Motors
If you've got regular acrylic mirrors, the glue should go on the gray protective backing, if you have front surface mirrors, the glue should go on the glass or acrylic side. With your mirror flat on a piece of kleenex or newspaper, place a medium-sized blob of glue on your mirror and put the motor directly into the blob. Try to make the motor shaft as perpendicular to the mirror as possible, human error will induce an incorrect angle that will cause wobble, the kind of wobble that we exploit when using multiple mirrors. Once your hot glue is dry on the mirror, you should test the spin to make sure the wobble isn't excessive. Ideal wobble should be very small, maybe 2-5 degrees.

Testing the Motors
Simply touching the red and black wires from your battery pack should make the motor spin. Just test them a bit to make sure the mirrors don't fly off, and you can see if the wobble is excessive. You can bounce your laser pointer off the mirror now, though you'll only get a single circle. The higher the angle of wobble, the larger the circle will be, these effects will multiply with each mirror, so a smaller reflection is best. If you're reflecting off a single mirror near the center of the circle, the reflection may just look like a rather fuzzy and thick circle, it will tighten and expand down the mirror chain.

Attaching the Risers I used k'nex pieces, but you can use anything 1/4" tall, flat, hard, and smaller than the motor itself. Simply hot-glue the motor onto your riser, and let it dry.

Step 3: Preparing the Mirror Layout

Notes on Layout
Lining up a laser beam for multiple reflections is a very delicate and tedious process. It's good to have a general layout of your beam path, and the orientation of the mirrors within your box. As far as gluing down each mirror, try to get each reflected beam as close to the center of each disc as possible. 

When laying out a laser path, the beam should always stay in the horizontal plane, this sounds obvious when planning a box like this, but it's important to note partially for eye-safety, but also avoiding excessive spread of the projected laser that will cause blanked areas in the final projection. 

The first picture below shows a very general layout of the beam path.

Cutting the Entry Port
The height for the hole in conduit box should match the center of height for the mirrors. Having the laser too high or low will cause the initial beam to not hit the center of your first mirror on fully inserting your laser pointer, and will make future reflections either hit the ceiling or base of the box. The horizontal distance from the side of the conduit box matters too, since the motor takes up some horizontal space.

Use a small drill bit for a pilot hole, rather than going straight for full size. This will help you test out how accurate your beam height and angle are, and allows stepping up to the right size for your port adapter.

Keep using larger bits until you're fairly close to the size of the adapter. From there, use the rotary rasp to shave down the edges of the hole until the adapter fits snugly - allowing it to fall all the way in, but the flared rim should hold onto the case. From there, you can place hot glue along the rim to hold it down, making it flush.

Step 4: Attaching Switches and Potentiometers

Installing them is pretty basic, drill a hole the width of the post for each potentiometer, but plan it out so they don't bump into the motors. These have a hex nut that allows you to tighten them down from the outside of the case. A lot of potentiometers have a little vertical nub that rises from the top of the potentiometer, but keeps it from being flush against the case, I just snap them off with needle-nose pliers.

#1 & #2
I cut each potentiometer hole 1/2" from the base of the conduit box through a side panel (see pictures). Thread them through, align their terminals towards the middle, and tighten the hex nut.

#3 & #4
These two attach to the top panel of the conduit box,and it's important to make sure the main chunk of the potentiometer doesn't bump into a motor, since it's really compact in the box. Simply place them in-between motors.

On/Off Switches
These allow me to completely kill power running to any individual motor. They aren't absolutely necessary to kill a mirror, since a potentiometer turned all the way on (Max resistance) will kill the juice anyways. Stopping the motor by resisting all the electricity rapidly drains the batteries by turning all that power into heat. They add quite a bit of complexity to this mod, and if you don't feel like going through all the work for installing switches, you don't have to, but I find them useful.

Each switch attaches just like the potentiometers, drill a hole and thread on the hex nut from the outer side. Each switch should be pretty close to its potentiometer, leave room for the potentiometer decorative knobs to fit on top of their posts. Those knobs attach by a tiny screw in the side of them squishing onto the post.

The images below show how the on/off switches are oriented.

Master Power Switch (The Big Red Button)
This switch controls the power to all four on/off switches, and acts as a kill-switch in case you need to turn everything quickly off. Realistically, the switch I got is complete overkill and over-sized for this project, but it seemed like a fun attachment to use. Again, see the pictures for where the switch goes through. I get some comments about how it looks like it's about to activate a bomb.

Power Plug
Take a 9v power connector, drill two tiny holes for the positive and negative wires to enter the box, put them through, and hot-glue it down. A picture below illustrates what I mean.

Step 5: Soldering Switches and Potentiometers

Since so much equipment is going into this box, it's best to minimize the number of exposed wires in the case. I use very short-length connections and hot-glue everything to the case sides.

My color scheme for wiring in the box is:
Red: Carrying juice from the batteries to a switch, and from a pot to a motor.
Yellow: An intermediary connection between switches and pots.
Black: Ground wires exiting the motors to the battery terminal connector.

How a Switch Works
Though the title is funny, it actually matters as far as three-terminal switches and potentiometers operate. When you take apart a switch, it's pretty similar to the image I have below showing a green or red ball that connects a side terminal with the middle pin. The middle pin is always connected, only the side pins truly go on or off.

As far a potentiometer goes, it's a bit different. They are intended to have all three terminals used when doing proper wiring, acting as a "reference voltage" between two of the pins. For the purposes of this project that doesn't matter, since we are dealing with simple on or off power for a single object, so only two pins are needed. Rotating a potentiometer handle changes the amount of electricity transferred between a single side terminal and the other two, so both of these other pins can receive electricity at the same time. When the middle terminal that we solder our motor to is truly "off", it's simply that all the electricity is going to the third, unused pin. Having the pot turned half way splits the power between the two pins, so our motor receives 50% power.

The first picture below shows a very short connecting wire between a pot and switch. The sides of it are heavily tinned, so it's easier to connect to a pot.

Getting Down to Soldering
In connecting a switch to a pot, use a short connecting wire between a switch side terminal, and a pot middle. Glue down the longer wires to the conduit box sides.
For the first two switches, I tried to minimize wiring and connect them together with a cut in the middle going back to the master switch. Looking back on it now, I should have just connected switch two to switch one, and had a second wire go from switch one to the master.

Soldering the Master Switch
Time to connect the power wires between the middle pins of all the switches, and the middle terminal of the master power switch. I ended up soldering a small stick of metal to the middle terminal of the master switch, since the four power wires from the switches make a large blob that could bump into the other pins. I ended up bending the side terminal to allow more room.

One side terminal of will have the positive of the 9v battery connector soldered to it. If you are using a big red safety switch like be, it would be the pin closest to you when flipping the switch (again, think of the green/red ball model). When the switch is flipped up, the power is transferred between the 9v positive and all the on/off switches. When the switch is flicked down, the 9v positive is left by itself, killing the connection.

This master switch is only making up the break in the positive path of electricity. When everything is done, the grounds from all the motors will always be soldered to the 9v connector's negative wire.

Step 6: Prepping Power

Prepping the Power Pack
As far as connecting the power pack to the conduit box itself, I use two separate 9v connectors. They fit into each other end-to-end, but as a complication the colors end up reversing when you do so.

Normally when color-coding wiring, red is positive and black is negative. If you look at a 9v battery the circle nub provides positive 9v, and the hex nub takes in the ground. It's the exact opposite for a 9v battery connector, and the colors make sense if you only use one connector.

Since we're using two 9v connectors, solder black to red and vice versa. I've made an image to demonstrate how the color switch works.

Testing the Power Pack
With your 2-AA battery pack connected to the conduit box's 9v connector, touch the wires to the terminals of each motor. These 1.5v-3v hobby motors don't have a positive or negative side, power can be given to either side but the mirror rotation direction will change depending on the wiring. Solder on 10" long red and black wires to the motor terminals.

Having mirrors rotating in opposite directions will more rapidly shift laser projections. Some users create a switch to alternate directions between the motor terminals, for more variation in patterns. Since we are using four mirrors though, we can do far more, such a hack is done more on two mirror spirographs than something like this.

If you have a volt-meter, connect your battery pack to the conduit box, begin flipping switches, and make sure there is juice flowing through. If you don't have one, you can guess in the dark by just connecting the motor wires and turning the switch and pots until it spins. I have a couple pictures showing the connectivity function on my volt-meter, which measures a resistance between 1(1000) which is no connection, and 000 which is full connection. When measuring juice from the 9v connector to the potentiometer, your resistance number may end up being simply a lower number, like 500 or 600, which is fine, as long as the number drops when the post is turned, and at maximum resistance the motor doesn't spin.

Step 7: Installing Mirrors

Notes on Beam Expansion
Don't let the projected beam take up too much of the entire circle of any of the mirrors down the beam path. Each projection will grow wider down the chain, just don't let it become so big it exceeds the area of any of the mirrors, meaning don't let the wobble be too large, and the projections should be centered on each circle. If you want to make it a bit easier on yourself, use the mirror with the least wobble for mirror one, and the most wobble on four.

Installing the First Mirror
We're finally going to install the first mirror, don't fully solder your wires to the potentiometer and ground yet, since we'll need to cut the wires to their proper length before permanently gluing them down. First just make sure it turns on properly. When powering on your mirror and holding it, remember that the disc is acrylic or glass, which when spinning at 2,500RPM can easily give you a good gash if your finger bumps into it.

Hold the motor-mount down in it's corner, place your laser into the adapter port, and turn it on. There should be a circle being projected onto a side wall of the conduit box. When you do end up gluing down the motor, you'll need to hold it until it dries to make sure your beam path stays in the horizontal plane.

Now that the mirror-mount has had its riser hot-glued to the base of the conduit box, cut the wires to the proper length. The red wire should be very short, since it's connecting to the pot immediately next to it. As far as the negative ground, I ran it along the bottom edge of the conduit box, under the adapter port, and ending up right next to the 9v connector wires. Solder your positive wires to a side potentiometer. As a note in design layout, make sure you're using the same side terminals for your potentiometers, so when you end up turning them the same direction (clockwise or counter-clockwise) power is provided or resisted without confusion. The ground wires should end up near the 9v connector.

Mirrors Two and Three
Repeat the process used for mirror one, making sure the beam path stays horizontal and your wiring nice and compact. This is the most tedious part of the project, as the box becomes more cramped with the motors taking up space and the newly soldered wires getting in the way. Plan out your wires so they don't hang anywhere within the beam path, as the projection would have gaps in it being blocked by the wire. This is more a problem in hanging in front of the adapter port than falling in-between the mirrors.

The Exit Window
I cut my exit window before I glued down mirror four, but still tested to see where the final projection ended up on the conduit box. Once mirrors one-three are installed, turn them all on to full speed (maximum beam expansion and wobble), hold mirror four in place with it fully powered, and see where the projected beam hits the conduit box. You have the most freedom with the final mirror, if your projection ended up kind of messy, you can always cut out the side of your box, or even a portion of the ceiling or base. For my projection, it was clean enough to hit the opposite wall from mirror four without requiring excess cuts.

When actually cutting the window, be extremely careful. This part can become tragic if you use a drill bit to punch through, don't let the bit drive through and hit a mirror, either dislodging or snapping it (which I did, and thankfully I made a fifth front surface mirror and mounted it in the event I screwed up). I've found the best way to cut a window is with a dremel and sanding disc. When sanding your edges down the conduit box, the plastic tends to become more molten rather than cut, along with making a funny (and likely toxic) plastic smell. Anyways, cut out the window, and if you've got a piece of plexiglass measure, cut, and glue it in over the new hole.

You'll need to blow out all the shavings and junk from cutting the window, and in the very likely event some specks are stuck to the mirrors, blow on them or very lightly brush them with a kleenex. As an educational note, whenever blowing air (such as to clean out a video game cartridge, or in this case all the plastic shavings), you can wipe your lips on a sleeve or shirt, so you don't blow saliva particles all over your very clean mirrors. Try to get the inside as clean as possible before sealing it up.

Step 8: Final Assembly

You should be able to experiment with your potentiometers and switches and have your beam project fully through the window. If not, you'll just have to fine tweak your setup until it does, and that may mean going back and re-gluing a mirror for less wobble, or cleaning up your wiring.

Hopefully everything works, in which case it's time to put everything together and be done with this box. When putting the top lid over the case, the extra lengths of wires tend to bunch up, so it's important to move them around before you completely close and screw it down. I had to make my positive wire going to switches one and two get squished between the port adapter and top lid.

Then get the screws that came with your conduit box, and tighten the top lid to the box itself rather tightly. It's very likely you won't get a perfect fit between the top lid, since it could be bumping against your adapter or whatever leaving a gap. This gap is fine as long as your tighten it down and everything works.

Have fun playing with your new spirograph, I've found laser projects look absolutely incredible in fog (either natural or man-made fog/smoke), and are fun for showing off to friends by projecting onto a big tree, a field of tall grass, or the side of a building. There really is no logical reason to build a spirograph, it serves no useful function or purpose, but it's a lot of fun to watch and share with friends as we talk about the weird patterns at night. Each mirror you turn on the image becomes more complex (and difficult to control), but when you get a really neat pattern with all four mirrors, it's a bizarre 3d projection of light that instills awe. I keep my box in my car for whenever some friends or strangers are bored, and I hope you can enjoy the same fun and beauty that emits from the little grey box.

Here is a bonus video, made by Instructables user JoeMonkey (Lollyliver), who has followed this guide and used a 400mW violet laser in his spirograph. It turned out so well, I think it's more crisp and accurate than mine.