tseary

Thanks for asking. I've designed a new minimal version without the IR receiver, and only a single servo output. Using the smallest SMT parts I could manage, the board measures just 12x24 mm. But I haven't ordered the parts yet, as I need to finish some other work before digging into this. The new design has a different microcontroller, so it will require fresh code.

I'm here for the transparent tires! I just picked up the Creator roller skate for the pink tires too. Maybe someone will find a nice way to illuminate the green tires too.

Thank you for sharing this. I had never heard of this mechanism before! It really looks like sci-fi tech; Borg or something... I wonder how this compares to the Stewart platform in force and range of motion. I'm guessing the Stewart platform has some kind of advantage considering how common it is. Although I can imagine this cube being applied in a modular robot.

@LabManager where did you get the MK servo from? I see MK servos being sold individually on ebay; I'm tempted to get one to experiment with (or dissect) but I'm not sure it's the right kind. As I understand from your first post, the only thing that changes the servo behaviour is frequency. 470 Hz gives +/-90 degrees, and >980 Hz gives proportional control. Did you try even higher frequency beyond 1200 Hz?

@gyenesvi Sorry, I didn't add any instructions yet. I'll try to do that during the week. A couple of short answers; the board is reflow soldered using solder paste and hot air. The chip is programmed through the ICSP header - this can be done using an Arduino Uno and the "Arduino as ISP" option.

Good idea. I was thinking just 2 holes, but if it were small enough it wouldn't need any. This is a good point. One advantage of servos over PUP motors is that servos know their absolute position.

I've made the GitHub repo for my servo controller public, and I also uploaded the KiCad files: https://github.com/tseary/Sergo The existing design is indeed 3x5 studs. With a smaller microcontroller, single servo output and no IR receiver it could probably fit into 3x3. Maybe I'll look into this tomorrow...

On the subject of converting C1/C2 to servo PWM without a microcontroller, this is doable... As a rough concept, I would suggest the following: 1. Convert C1/C2 to analog by RC filter. Combine these two signals into one with an opamp subtractor. 2. Generate a PWM for the servo from a 556 timer. (The 556 is two timers. The first produces a constant frequency to trigger the second timer, which is configured as a one-shot). 3. Let the combined analog signal determine the pulse width of the one-shot timer. The result is the servo signal. There are a number of issues with this approach that are solved by a microcontroller. Foremost is that it would take at least double the space - although it could be a few cents cheaper in volume.

I've done something similar a few years ago to connect hobby servos to Power Functions. (In the image below, a 2x5 studful Geek servo). This custom PCB has an ATTINY84 microcontroller to read the C1/C2 PWM and drive the servo accordingly. There is also an IR receiver which allows direct control without a Power Functions receiver.

Wooooooah! That FPV car is awesome! I was thinking of getting an ESP32-CAM for machine vision stuff but I didn't realize it can stream live video. Long ago there was an online simulator game in which the player controls a Mars rover based on images sent back from the rover. The game had a simulated time delay to represent the transmission time, so you had to program your movements and then see the result. I always thought it would be cool to make a real version where you control a model rover in a different room.

This is a good idea! I recently discovered the trick of using a 12T gear as a hub inside another printed part. The teeth are engaged with a matching spline, so there is little risk of damage. For hole size, I've found that 5.0 mm makes a firm fit for friction pins (when printing vertically). Axles will go through, but it's too tight to spin freely. I use a 6.2mm diameter x 0.8 mm deep counterbore on each side to fit the collar of the pin.

I haven't had any prints fail, but they aren't seeing hard use either. Perhaps someone who builds RC cars can remark on 3D printed gears or other parts in a tougher environment. I'm not up to date on the different Enders, unfortunately. We recently got a Bambu at work - I'm not the one running it, but the print quality is great, and it's fast!

I also have an Ender 3 V2. Although it's a few years old now, it's still going strong with minimal maintenance. The only upgrades I've done are to add a Capricorn tube and replace the bed springs. I use it to make custom Lego gears and liftarms from time to time. Today I'm printing a mount for a 540 size DC motor. One of the best filaments I've used is Duramic PLA+. I suspect it has a bit of ABS in it, because it prints at a higher temperature and the finish is a nice match for black Lego.

@Lipko It's generous of you to subject your models to that! It would be a nice treat for those kids to get their hands on some Lego, where the norm is "look but don't touch". I don't know if I could do that; I'd be watching like a hawk. In the video clip it seems everyone is well-behaved, but I'm sure you discovered some weak points in the builds. Was there any damage?

Go ahead! I have a couple more on Flickr: https://flic.kr/s/aHBqjBN7TB