Interrupts on Arduino introduce random ~10µs jitter, which is roughly consistent with the jitter amount in your tests. For tight timing, try to disable interrupts during the laser toggling and instead wait for the sync pulses from the photodiode by directly reading the pin register in a blocking while loop. The serial communication can be done between frames while waiting for the frame sync (if necessary, this will add one more disk rotation with laser off as a "blanking" interval).

Showing the prototypes and their issues is very educational. Great job !

I love finding new channels like this. I can’t wait to see what he makes. It’s really fun watching a channel evolved from just a few videos

Hey great video, i'm just a layman hobbyist but the way you work through your project outlining the errors and mistakes you encounter along the way and rectify them (rather than editing them out) really makes your content shine with extra value for me!

Really neat project, thanks for sharing- the parallax effect when shining it into the corner of the room was especially neat, really different to how a normal projector looks

When I was a kid, my dad built a cool persistence of vision display with LEDs. Not a projector, but it made it look as though a LED marquee display was floating in the air over the device. It used those same optical transistor switches. This was in the early 90's, he envisioned miniaturizing it into a small ball to be used as a christmas tree ornament. He never moved further than the prototype, and a few years later similar devices were available retail.

One of the best projects I have seen in the last months. Amazing!

I love the gritty analog look and the wobble effect!! Very retro sci-fi.

If you don’t use tarduino delay functions but rather use noops and direct port writing you should be able to get a laser toggle every 2-4 clock cycles. You may want to invest in a MOSFET gate driver IC though.

This is a super well done video! Extremely informational, but you did a great job of breaking down some of the more advanced concepts and presenting them in an easy to understand manner. Such an incredibly cool project as well!

This is a fascinating project. I also wanted to mention that your style of code walkthrough was very effective. Best wishes to you, and keep up the good work!!

Dude, This is AWESOME !! To me the flickering and wobbling add a special sci-fi vibe to your texts rather than a flaw. Loved it. All the best. Keep going.

Content like this still makes UKposts great.

I love the retrofuturistic cyberpunk aesthetic of the scan lines and slight wobble. There's also a lot of tricks in both software and hardware to get better resolution. Definitely look into faster chips, the ESP32 is great in that regard. You could also use a shift register or serial control chip and external clock to control the beam pwm. Basically write your bytes into a register, and clock out bit by bit directly to the beam control. That will give tighter temporal accuracy as well.

Love this. Also kudo's for explaining your struggles to get this going and for your tenacity.

One of the first projects I thought of was a laser projector. Love it.

This is a really awesome project, Ben, and a nice combination of old and new projection techniques! I can tell you that one part of the causes for the shuttering effect you noted actually is the carousel that you built, as each transition causes the image to "break" for a split second. You'll also get closer and more uniformly focused lines if you anchor the pivot point for your mirrors at the center height of those mirrors and in line with your laser. An interesting point to note is that a lot of larger home theater projectors use micromirror devices with broad 2D micromirror arrays within, one for each raster pixel art either the intended full resolution or some simple fraction thereof (and then vertical and horizontal servos in the latter case to multiply the apparent pixels); but many pico projectors use a module with just a single micromirror on centered vertical and horizontal pivots. My own limited understanding says that's identical in concept to the galvos in light show projectors and they just use tighter control. It might be fun to see what you can do with that knowledge.

Nice work! I love seeing the process. As satisfying as a 30 second montage is, it's important that people see that big projects take time and patience. Take my sub good sir, I look forward to what you're going to make next :D

I've seen a few different variations of this type of design, and I actually tried to make my own a few years ago! At one point I used a mini disco ball to get the mirrors. The version I made was wobbly with similar problems to your first prototype but I never took the next step to fix all the issues. I'm impresses that you stuck with it and actually got it working that well. Nice work!

Love it! Reminds me of the old monochrome green phosporous crt displays, what i always found very nice!

Excellent production quality for a small UKposts channel. Engaging and interesting from beginning to end. Nice work.

Awesome. Great to see how this may develop in the future. Keep the ideas coming, Ben,

Instantly one of my favorite channels now! You know what? Make a hologram with it? Some holographic projectors use an array of speakers on top and bottom, to create a levitation field. Then they use a small white bead(sphere) as a "pixel" representation. Then there is a camera that tracks the small sphere and projects a laser light on it. The resulting image is a actual physically interactable 3D hologram!

I love the glitchy effect on the text, it's so real! I think ots perfect if you can just make it half as tall with smaller screws and 3d prints

Thanks! Been pondering trying this very technique for a while. Very interesting to see the issues and the design iteration re angling of the mirrors.

Really impressive Ben. Well done on the persistence too. couple of ideas for your future versions. 1) Not sure about the availability of red and blue laser diodes that could have their output balanced with this green one, but RGB would be awesome! 2) how about using the super-fast HDD heads arm in a vertical orientation, with a small mirror on the top. you could use it between the diode and the spinning mirrors to dynamically apply micro vertical adjustments by your microcontroller, so you could programatically control the up-down scanline sweep, rather than manual mirror adjustments?

Damnit brother, I wasn't halfway done with your video before I subscribed. You're relentless and I cannot stop getting enough! You're awesome!

I really hope to see more of this project. Awesome work!

Impressive results! I wouldn't have expected a 3D print to be stable enough, it's nice to see that a commercially-made polygonal mirror isn't the only option. But you don't actually need a faster CPU: The arduino you're using would be perfectly capable of precise 62.5 ns resolution pulses -- i.e. the full 16 MHz system clock rate -- if you exploited the Atmega328p's powerful Timer/Counter peripherals for the task. Here's how I'd do it: - Set up the 16-bit Timer1 peripheral in free-running mode (WGM mode 0) and with full system clock rate (i.e. no clock divider). This timer will just count up continuously; the fact it'll overflow from 0xFFFF back to zero every 4.096 ms is of no consequence as long as that's longer than a single scan line. - Wire the per-scan-line trigger to the ICP1 pin. This way, the input capture module can record the exact "start time" for each scan line _in hardware_ before triggering the input capture interrupt to set up at the start of the scan line. - Wire the laser to an additional XOR gate, whose inputs are wired to the OC1A and OC1B pins. The output compare channels will be used in 'toggle' mode so that, in conjunction with the XOR gate, they can effectively act as a single output with a two-element buffer, rather than two separate outputs with only single-element buffers. - The main task of the input capture interrupt (TIMER1_CAPT) is to copy ICR1 into a register, and then copy of the next line of the image into a separate buffer, adding that ICR1 value to each element of the buffer to offset it to the measured start time of the scan line (using 16-bit unsigned arithmetic so it overflows back to zero the same way the timer does). Aside from that, it's just a bit of bookkeeping at the start to reset the outputs to a known state (set COM mode to 'clear' and trigger FOC), and a bit more at the end to prime the output compare modules (set OCR1A and OCR1B with the first two values from the buffer, set COM modes back to 'toggle', and enable both compare match interrupts). - The compare match interrupts (TIMER1_COMPA and TIMER2_COMPB) then have a very simple task: each time their channel finishes triggering, retrieve the next value from the scan buffer and put it in their OCR register. That should be the absolute first thing the interrupts do, and then after that there's only some light bookkeeping, to clear their interrupt enable bit if the _next_ next value would be past the end of the buffer. - The interrupt for the index trigger is even simpler still: all it needs to do is reset the value of the row counter back to zero... and I guess you could flop image buffers here too; change the pointer the scan line interrupt uses to find the image to point to the frame that was being rendered while the previous frame was being displayed. The way I'm proposing to use the interrupts here is in a sense the most fundamental design pattern used for serious interrupt-driven embedded programming. Almost all hardware peripherals are specifically designed around this usage pattern, understanding that fact can make the rationale for their designs much easier to understand. Even though an interrupt seems instant compared to polling, there's still too many sources of jitter to rely on them to take actions that require precise timing. Rather, their responsibility is just to refill a hardware buffer from a software buffer before the hardware runs dry, or empty an hardware buffer before it overflows -- something that still has to be done "right away" rather than "next time the control loop feels like checking", but that way an extra microsecond or two of delay waiting for another interrupt to finish doesn't compromise the timing accuracy. This pattern is actually used twice as I describe it above, both copying data from the ICR1 register to use to populate the scan buffer, and of course moving data from the scan buffer to the OCR registers. With the design, you'd inherently have the full 62.5 ns precision of the full-speed system clock, and using both channels together means pulses could be as short as a single clock cycle, too. The interrupt execution time would limit the rate at which you could continuously switch it on and off, but even with minimal effort I'd expect at least 100 kHz. With high effort (i.e. implementing the compare match interrupts with hand-written assembly code) it'd be entirely plausible to achieve a maximum continuous pulse rate better than 1 MHz.

You can also glue small, front-surface mirrors to small speakers and bounce the laser off of them. By using the right combination of signals you can do, X-Y vector graphics and text.

Fantastic start to a channel! I'm eager to see what other projects you'll come up with :)

dude, insane build.... this is wild. im impressed

Great job! The wiggle of the text is similar to the splash screen of games on old computers like the ZX Spectrum. You can project your text or image onto a horizontal series of falling water drops or solid flowing water in the form of a flat waterfall so as not to fight the wiggle but to make it an "interesting feature" of your project.

I just stumbled on this. Very cool. It reminds me a bit of the old mechanical televisions. What was wild is that your final design looks a bit like a "Mervyn 30 Line Mirror Drum". Another idea might be to look into a "mirror screw." At that point if you can get PWM driver for the laser, you could even display rough images.

I can imagine the level of persistance needed to finish it. Incredible stuff. earned a subscriber here!

I've been wanting to make this since a very long time. It was fun to see you make it. I was thinking about adding a secondary rotating mirror for the vertical movement, but you made me realize I would only need one. Anyway, looking forward to a better version of this.

18:36 this shot looks really cool. It looks like a simple image slapped on in post production but the reflections of the laser show you whats really going on

For switching the laser you should use the 16 bit timer and do a timer compare interrupt. Set the prescaler to something that gives you adequate range and accuracy. Then just update the compare register to get the laser pulses you need. Remember to set the timer to reset on compare match

Super cool! I'm glad to see this project getting the attention it deserves!

I wanted to build just this about 20 years ago. It was explained to me that it would be a bad idea compared to galvos, because the laser would spend a lot of time off, which means most of the light energy would be wasted and produce a relatively dim image. But how fun it is to see it working regardless.

I absolutely love this idea. And im wondering if you could use smaller mirrors and maybe stack them for multiple lines of text? I wanna build one as well but im limited by budget and knowledge of code lol so i hope you make another video

Cool project !!! Some suggestions: Use 2 hall sensors with embedded magnets for possition, less air resistance is less noise and vibration. And your unballenced extra arm.... I would use shims and a screw for tight compression together with lock tite that screw. The shims define your angle. You can make a stack of different thicknesses and adjust very precisely with no movement whatsover. You could use the remote controll engine of the ESP32 for laser controll + you get wifi and ble for free. You could offset different colors and adjustd the scanline for the laser offset or create a multi color single point first.

I built something similar a few years ago but it was for a diy laser projector. I instead had the lasers go through a dichroic mirror setup (for combined color), hit the mirror wheel, then hit a mirror that was attached to a planetary gear output with a motor that had a cui encoder (to control beam angle). I used an fpga though for controlling the drawing. I used a resin printer and didnt have to adjust my mirrors on my mirror wheel. I never finished the whole project due to lack of fpgas at the time (was trying for atleast 4k but was stuck at 2k due write limits due to fpga clock) and not correcting the beam sizes for the 3 laser diodes but this had definitely peaked my interest when i saw it.

Love the project, presentation and videography. Keep it up!

Cool project! Decades ago I also had a notion to build something like that, but 256x192 (sinclair's screen, you know) with two rotors for frame and line respectively (50Hz, 16+KHz). MC's back then were too slow, but we already had some PLAs, so it wouldn't be a big deal. The main stopper was the mirrors fabrication precision needed. There was impossible to find needed machinery, so the project died far before any in-iron implementation. It's cool to see that now it's possible with no that much effort.

Congrats. I did a similar 32bits/line laser projector 3 or 4 years ago. The only way I managed to get it to work was by using "thermally stable materials" all around. Equally stable mats in the linear and non-linear domains too. Therefore no composites, lots of exotics, not to mention quite a bit of carbide endmills consumables and crashes. I liked the HDD silent motor idea! Good vid, keep it up.

I don't have the time to invest in the learning curve to build this, but love the effect and would buy one right now if the product was available to purchase. Great work!

Your channel has potential. Keep it up Ben! 🙌

You invented a paperless laser printer. 😋 But seriously great job.

Muy bueno tu proyecto, yo soy nuevo en arduino y aunque no entendí muy bien, me pareció increíble seguí así 👌🏻

Very nice work - thanks for letting us know what obstacles you found, as we all learn from each other. Some of us bold fail and build again. It is nice to see a win from time to time.

Good luck and all the hardwork that went into into the project

This is very similar to how the laser scanner assembly in a laser printer works. The laser is controlled by an analog video signal. Also, using front-surface mirrors may sharpen up the images.

Amazing project! :) You could try altering the mirror angles in a cross pattern, so the point of mass would be equalized by the point of mass of the mirror on the other side of the wheel. This would also mean your code would have to change to render the lines in alternating manner from top/down to middle, instead of just top to down. Try doing anything you can to reduce the vibrations. It will help with wobble a lot.

Magnificent project. Clear logical thinking. Very well done!

I figured he would use two sets of moving mirrors to achieve the raster effect like most show projectors but I'm impressed by the simplicity of the adjustable rotary mirrors.

You could possibly save and cut code complexity by only using one sync sensor (the top one for full rotation ) and divide the result down to x mirrors. This would probably net you a possible higher rotor speed and less power consumption by the motor for less resistance by the little fingers on the bottom.

Cool project! To reduce the number of interrupts (and input sensors), perhaps you could omit the ISR_rev() function, and when you need to get the current mirror index, use a modulo-8 operation on mirrorFlag. This operation returns the remainder of a division rather than the actual result, which would be your current mirror index every time, regardless of the mirrofFlag count. Should be true even in the event of an integer overflow, as long as it's unsigned. Alternatively, what if you just reset the value to 0 in ISR_mirror() every time the value reached 8?

;Interesting project and very impressive. I've never really appreciated how fast code actually runs, but considering how insanely fast the lazer needs to be on an off.. yet you can easily add logic, variables etc. It shows how insanely fast processors are !!

I've watched a lot of your videos. This one was so awesome I finally subscribed. Thanks for the program.

Pretty impressive results! A couple of ideas to improve, I'm not sure if they would be practical to implement. To stop the wobble, use a fast photodiode and a mirror in the output path of the laser, to synchronise the laser switching with the actual position of the laser beam. Have it inside the housing, laser turned on until it hits the photodiode, then quickly turn it off before the beam reaches the start of the opening. The switch faster, use the hardware UART and encode the character table into bytes, that would limit you horizontally to 8 pixels per character, unless there is a mode that has no start nor stop bit

Wow well done Ben! It's pretty hard to challenge the cost of a large screen TV for a display system but for things that only need a one or two line display this might be the ticket. Sporting events? Business meetings? Directional signage?

Nice project, thanks for making the video.

Well done! I have been envisioning a very similar project for a couple years and never got around to it. This is a really clever implementation. +1 on the advice to ditch the Arduino. Maybe a Teensy 4 would be a good candidate, thanks to the Cortex M7. If you're feeling really ambitious, you could also switch to a hobbyist FPGA, like an Alchitry board or a TinyFPGA BX. Also, maybe you can order a planoconvex lens from ThorLabs or Newport to tighten up the resolution? Again, amazing stuff here!!

Handheld barcode readers have a little mirror oscillating in them. Use that insted of the hard drive. To have multiple lines - use another one with a lens to restrict it's angle / or use 12 cheap lasers. Also switch to esp32 - much faster, has bluetooth already, can act as an AP to provide a webpage for settings. Good job!

Love your channel. Can't wait to see what else create!

I would love to make my own! Feeling really inspired by your channel.

You've probably already found what you need to fix the timing issues, but my suggestion would be to use the AVR timer/counter system directly rather than using the Arduino functions. Refer to the datasheet for the AVR model you are using for details. There are a variety of approaches to get what you want, but generally you would set the timer in countdown mode, enable the timer ISR, and set the compare output mode to toggle on compare match (PWM mode). In the ISR load the count for the next toggle time. The timer/counter configuration takes a bit of work to understand, but once you get it it's a very flexible and capable system that should be more than sufficient for what you're doing here.

Very nice. To avoid the need for timing adjustments in code for the scan lines, and perhaps to fix the wobble, you could try a sensor assembly just before the output window. Its purpose would be to detect the beam and start timing based on that. A light guide of some kind to a single detector might work. Power the laser at the start of a sweep, wait for a signal from the detector, and then the horizontal position is time relative to that. Have a single adjustment in code to account for any skew in the detector, which could be set through a web interface if you later used an MCU with WiFi such as an esp32.

very cool, unique project. excited to see what else you've done, subbed for sure.

Really awesome project ! i like how you filmed and narrate the video, also you didn't give up and build comething that actually work. Good job and i hope you will make a project 4.0 and a video about it ! Another susbriber :3

That was awesome. Thank you for the time and work.

I've wanted to make this for so long. Good job !

This is an interesting take on laser projection. I have thought about trying to build one, but always figured I would use two galvanometers (the head servo in the hard drive) one for X and one for Y. There is always more than one way to solve a challenge. Great work!

Extremely awesome video. I'm sure it was lot harder than you make it appear to be. You rockk.

Damn, hell of a project! I like how you handled the several mistakes that would have happened to me as well...such as the camera not focusing while everything else was falling apart lol

I vaguely remember reading something about holographic lens being used in Supermarket POS scanners doing a similar job of scanning a large area without the need of expensive optics.

Awesome, Thanks for sharing

"death star surplus parts" moment was an instant like for me 🤣 Anyway, awesome idea. I like it 👍

great video ben, ill see in future but im completely sure its a great add

Awesome video Ben! Can’t wait to see what ur making next.

Cool stuff man, thanks for the video.

I love that you said you have to see it in real life. Everyones sees it differently.

Hello Ben! Excelent work! Its a amazong idea! Congratulations!

The wobbling honestly looks awesome. Very cyberpunk. Personally i would space the lines just a little bit further so the letters can be a bit taller.

This is dope. Love it

DUDE! You deserve at least my Like and Follow! 👍🏻😉 Good experiment! Love it!

I just subscribed listening to the intro music. Cool project btw.

excellent project!!! thanks for all the time you invested.

Man o man you are a genius! That seemed like a headache of a project.

Okay this project was awesome.. never seen this channel before but I immediatly subscribed.

Its kinda cool how it jitters a little bit back and forth. Gives it cyberpunk vibe

Damn wtf that's awesome!! I grief for MORE!

This is an amazing feat! Well done!!

The intro music kinda reminds me of Airwolf!! Cool project for sure 👍

I love the wobbling effect, it looks like this thing came from the Matrix.

Great video and project! Good job, dude.

Love the project!

respect for your hard work

This intro was epic loved the sound ;)