# Automatic Laser Spirograph (No Programming)

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In this instructable I will show you how to make a laser spirograph that changes forms automatically, and without the need to program an Audrino. This is accomplish by the use of 3 almost identical circuits that controls the 3 electric motors.

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## Step 1: How It Works

As you can see in the picture there is one circuit board with the tree individual circuits, three motors (two computer fans and a normal motor) with mirrors attached, and a green laser pointer. I use a laser that has a switch instead of a button, so I can leave it on while I enjoy the show.

Like I already pointed out, in each motor there is a circular mirror. These mirrors are from disposable dental mirrors, because they are already rounded, have a nice size and are easy to work with. The mirrors are glued in a coaxial way with the motor, but they have a small tilt. When the laser strikes the spinning surface of the tilt mirror, it is reflected forming a circle. If this circle is projected into another spinning tilt mirror it will form a variety of shapes, depending on the motors velocity and other factors. Adding a third motor just opens the possibility to even more complex shapes.

If you want to see it in a more scientific way, the resulting shape is the plot on polar coordinates of the following equation: f(r,ø) = A sen (x* ø) + B sen (y* ø) + C sen (z* ø). Were “A”, “B” and “C” are the amplitude that is the mean of how much the mirror is tilt, and “x”, “y” and “z” are the velocity of each motor and the offset between them.

So to be able to change the shape that is plotted you need to change the amplitude, the offset or the velocity. I can’t think of a simple way to change the amplitude, you couldn’t control the offset unless you used stepped motors and that is out of my reach. So what I did was to change the velocity of each motor.

## Step 2: The Circuit

Each motor velocity is controlled by an individual circuit using Pulse Width Modulation. You might ask me why I used PWM, and I will tell you that I choose to use PWM because in an early stage of the design I was controlling the motors with variable resistances, and I couldn’t reach the range of velocities I was hopping because the motors stop working in an early point. When you use PWM you can make every pulse as apart as you want and the motor wouldn’t mind because you are given it a boost of power, so you can make it go as slow as you want. (I don’t know if I make myself clear, if not you can ask me in a comment).

I used a simple timing circuit to make the PWM using the famous NE555. But this circuit would always deliver the same pulse every time, and I wanted to be able to change shapes on their own. So I decided to feed the timing circuit with a triangular wave that will change the settings of the PWM. To generate this wave I used a Dual JFET operational amp. And to make it even better, the triangular wave for every motor circuit is different. This is accomplishing by changing the capacitor in the circuit (C1).

## Step 3: More About the Circuit

The values for each component I used are as follow:
R1: 270 kΩ
R2: 220 kΩ
R3: 100 kΩ
R4 = R5: 300 Ω
C1: 47 μF, 100 μF, 150 μF
C2: 3.3 μF

If you have work with the NE555, you will notice that the values I used are pretty low; this is because I wanted a short pulse that can be trigger very close together or far apart. Also if you see in detail both diagrams, you will notice that I used different voltages for each part of the circuit. This is because I couldn’t find any other way to make it work. For the power supply I used an old computer power source (I used +12V, -12V, +5V, -5V and Ground).
The motors are connected to each NE555 output (Pin #3) and ground.

## Step 4: Final Thoughts

I didn’t use a big tilt in the first two motors because the circle shape could be bigger or “fall off” the next mirror. But in the last mirror the tilt is much bigger and gives a nicer end effect. I used double side tape to attach the mirrors to the fans, and hot silicone to the motor. Also be careful to put the 3 mirrors and the laser to the same height.

If you see in the pictures, the laser strikes the first mirror in a 45° angle, so the reflection will exit also in a 45° angle in to the next mirror and so on. You don’t want to attach the motors to the case in a very permanent way until you have tried it out, because the angles may be a little off and you will have to fix the positions of the motors.

And finally I added a screw in the front so I could easily change the whole thing tilt like a projector.

Thanks for your attention. Hope you enjoyed this Instructable, I know I did. :D

P.D: Sorry about the low resolution video, but it was the only way I found to show the true nature of this laser show. In higher quality it looked weird, maybe something about the fps and the way this works...

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## 21 Discussions

im using a 12 volt 1amp dc adapter i connected the power i blew up my ne555 chip sorry to be pain

Ok, several things. First: The 555 can work with up to 16v, so I dont think your adapter blew it. Second: I said that the only way this circuit could work is by using a desktop computer power supply because you need +5v, -5v, +12v, -12v and ground (you need all of them!!!). And third: the 555 can only source up to 200ma to the fans/motors, so if the motors consume a greater amp you´r gona blew the 555. Hope this helped.

hello sir

I can't find voltage of capacitor and there are kind of capacitor with different voltage , please tell me about their voltage that use it in this circuit .

Hi. If you see the power supply, the max voltage I used is 12v. So the min voltage for the capacitors are 12v, but I used 24v or higher.

Thanks for you comment.

Hi again.
I was wondering: would it be possible to make a photo of the back of the board, so that I can check all the connections compared to what I have soldered?
Thanks!

I'll look into buying an oscilloscope someday, sounds really usefull.
However, for the time being, I'll just mess around a bit and figure out some electronics. Thanks for the tip.

Thanks!
I misjudged the grounds, whereas I thought the ground + and ground - of the TL082 went to the motors, however now I understand that one end of the motor is connected to the TL082 and the other is connected to the NE555, that cleared things up for me.

Hopefully I will now be able to complete the project :)
Thanks again for the help!
PS: I have a simple digital multimeter, with a beep-sound indicating positing to simply check if a connection is good and nothing gets short-circuited.
PS2: somehow I can't reply, but have to type a new comment, because otherwise it gives an error of typing the 2 words.

It dosent matter that you have to post a comment every single time. Im here to help ; )
If you are into electronics you should think in buying a good multimeter (Im a noob and I have 3 different kinds, jajaja). And when you get a little bit more serious you should buy a oscilloscope. There are some fearly cheap on ebay that you plug to the computer with USB and works really nice.

Many thanks for replying so soon!
I encountered a problem, what I was afraid of, as being new to electronics.
From what I can tell, all connections are good, I get the + and - 12 and 5v power.
No shortcircuits.
I assumed that the TL082 grounds go to the motors (+ and -), but perhaps I am confused there?
My multimeter says all connections are okay, but the grounds - and + don't have a signal.
Should I apply the +12v and -12 from the power in and loop it to the motors?

I dont understand what you mean with your last sentence, but any how... Are you making your readings with a digital or analog multimeters? Sometimes digital multimeters cant give a reading with some frequencies.
You are correct, the motor goes between the output of the 555 and the ground of the TL082. Also, you have to use the ground of the power supply to the ground of the TL082. If you can get your hands on a osciloscope it would be great. Hope this helped.

Many thanks for your awesome instructable!
I'm gonna make a special birthday party for my mother in law who's gonna be 50 soon.
Besides music, I'd love to do something cool with a laser pointer, and came across this build.
I thought I'd give it a go, but my knowledge is very limited towards electronics.
Now, I figured out where to solder all the resistors and capacitors, and the 5v and 12 + and -.
However, I didn't figure out what lead to solder from the TL082 to the NE555 and what the 'fork' symbol stands for (couldn't find it on google, but my guess is it has to do with the 3 circuits connecting each other?).
I'd be very gratefull for any help, and it'd be awesome to get this working.