3D Printed DC Motor Laser Galvo

give me a minute it's 4am lasers let's say that you wanted to draw out a 2d image using a laser one way you could do it is by mounting it on an xy kinematic system like this and then physically move the laser around to draw out an image however there has to be a better way there is a better way laser galvos a laser galvo operates off a very simple principle if you have a mirror and you have a laser the angle at which the laser the laser beam is reflected off that mirror is equal to the angle which strikes it so if we strike a mirror with a laser beam at a very shallow angle it's reflected off at a shallow angle however if we strike it at a very steep angle then it's reflected off at a steep angle so by changing the angle at which the laser is allowed to hit the mirror we can control where the laser is pointing if we add a second mirror one for the y axis and we keep our x-axis mirror then by changing the angles we can change where the laser beam is pointing we can control how the mirrors are rotating using a stepper motor however the problem with stepper motors even though they give excellent positional accuracy they aren't very fast we can't rotate the mirrors extremely quickly and draw an image very quickly now normally this isn't a problem because in 3d printing whether you're centering metal or you're curing resin you don't need to go quickly in fact the opposite you want to go slowly so laser gauges using stepper motors aren't a problem but let's say that we wanted to project an image onto a wall or a piece of glass or do you make a hologram somehow then we need a laser gabo system that can very very very quickly at least 30 times a second draw out an entire picture we can't use stepper motors but what if we can combine the principle behind a galvo with a dc motor or an esc let's try it everything was printed in 0.2 millimeter petg on my ender 3. to make a custom mirror i used one-way mirror reflective film it's made for covering windows a little bit of super glue helps hold it in place to hold the motor i used a compliant grip the rotor attaches [Music] and a bolt helps lock everything in place the key to this project is a photo resistor it acts just like a limit switch whenever the laser passes over it we'll get a signal on the arduino this will allow us to figure out the rotations per minute of the motor and the exact position of the laser at a given time we use two photo resistors one for the y-axis and one for the x-axis in this particular design we'll be using a stepper motor for the y-axis the laser diode mounts in place on a 3d printed part which is held onto the stepper motor by friction these little laser modules are extremely easy to use in fact easier than an led because they have their own built-in resistor i decided to use a stepper motor for one axis on this experimental prototype but this really wasn't necessary and i didn't end up using it you could use another dc motor or esc motor in place of the stepper motor for this axis however this requires that you square the speed of your motor to maintain the same frame rate it's not a mems oscillator but it's okay for now my work desk is a dresser and since i hardly own any clothing i can fill up the drawers with tools ever since i was 10 years old and saw the eev blog video on how to solder i wanted a nice soldering iron specifically a hako and recently i got my way it's ironic that the first thing i had to use it for was punching a hole through plastic which i forgot to put into the cad design in the future i plan on doing a lot more soldering specifically i have a design for a software defined oscillator that can be used for high voltage power supplies we're using the standard method here for running the photoresistors which involves a 10k resistor the photoresistor and fixed value resistor together act as a voltage divider and the voltage is detected by the arduino on an analog pin everything is hooked up to an arduino nano and we can control the speed of the motor using a pwm module i'm using a 12 volt computer power supply here when we turn off the lights we can see the line that the lizard creates as the motor rotates the mirror because the photoresistor is hit at the beginning and the end of every rotation by the laser beam we can use this to calculate the speed of the mirror as it rotates as well as the position of our rotor at any given time i wrote a function that found the rpm during each cycle then averaged these values together and reported them over serial it can also report the average degrees per millisecond this is much more useful in calculating the position of the motor at any given time because if we know how long the motor has been running and its speed then we can calculate exactly where it is this is the result it spends the first few seconds figuring out its rotations per minute as well as the home position then it tries to paint the pixel directly in front of it each pixel is one degree wide the results are definitely not perfect and there's much room for improvement it turns out you can buy tiny mirrors off amazon in the form of disco ball covers this is really perfect for our application and i'll have plenty left over petg is well known for its inability to work well with adhesives so the foil mirror was very easy to remove once off i replaced it with the tiny five millimeter by five millimeter mirror and then i jostled it in place in the future i'd rather 3d print a recess to put it in the change in spot quality was apparent and shocking in the future i'd really recommend using these mirrors instead of the film considering how small these mirrors are it looks like i'll have to shrink down on this device a few orders of magnitude i still wasn't able to get good results and i believe this is the result of the inconsistency of the photoresistor in the future i'd like to try using an encoder in its place i imagine that this design might also be useful for laser scanning or laser marking a laser system like this would be very well suited for a heads-up display projecting an image onto a visor or piece of glass on a vehicle right now i'm waiting on a new lens for my aluminum 3d printer so expect videos on that in the future i'm also working on a video on how to convert an ender 3 into an ecm machine that way you'll be able to cut aluminum steel pretty much anything so stay tuned

Channel: 𝕄𝕠𝕣𝕝𝕠𝕔𝕜

Views: 17,656

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Id: UdwulGN7TTk

Length: 6min 53sec (413 seconds)

Published: Tue Feb 09 2021