This DLP 3D Printer Build Is Going Really Well

We suppose [Dan Beaven] got up one day and said, “I’ll make my own resin 3D printer, with resin management and an advanced separation mechanism!” It’s a build log that shows just how possible it is to roll your own resin printer.

Prints on a dime!
Prints on a dime!

The machine isn’t finished yet, but the example prints coming off it are already very impressive. [Dan] stopped the print midway to get this photo of the detail on the stairs in the standard rook torture test.

[Dan] wants a lot of features from his machine that some of the more polished commercial printers are only now offering. One really nice one is the sliding and twist separation instead of tilt. This will allow for cleaner separation between layers during a print, a lower failure rate, and also faster print times.

He also added resin management with a peristaltic pump. This reduces the size of the build vat, and less resin will be exposed to the elements and wasted. It also means that the printer can run unattended. In the resin handling area of the printer he’s also added a carbon air filter. This lets him run higher performing resins without gassing him out of house and home with fumes.

We like how [Dan] just runs right ahead and puts the printer together. He even points out kludges on the machine that are holding it together long enough for him to print a more functional part for the 3D printer– on the 3D printer. We look forward to the next installment.

Learning ARM Without Dev Board

There’s a tremendous amount of value in using pre-built, known-good development environments. It saves you hours of potential headaches when things aren’t working. Is the bug in the hardware or the software? If you bought a dev kit, you can be pretty sure it’s your software. But sometimes using a dev kit also feels like there’s a black box in the system. [Kevin] wanted to peer inside the black box, so he ordered a tray of cheap STM32F103 chips on eBay, and did the rest himself.

“The rest” isn’t all that much, but figuring that out is half the battle. [Kevin] soldered the TQFP chip onto a breakout board, added some decoupling capacitors, and connected four pins up to a dirt-cheap ST-Link programmer clone. The rest of the article describes the toolchain he used to compile for and program the chip. The end result is, natch, a blinking LED.

If you’re a bit experienced with microcontrollers and want to dive head-first into an ARM chip, [Kevin]’s writeup is just the ticket. In a single (long) blog post, he walks you through all the steps. If this is your first rodeo, you might be tempted to cheese out and buy a pre-built board on eBay (search “STM32F103” and you’ll find many options to choose from) and we don’t think that’s a bad idea either. Still, there’s just something to be said for the confidence that you’ll have once you’ve built the whole system from scratch.

How Does a Buck Converter Work Anyway?

[Great Scott] should win an award for quickest explanation of a buck converter. Clocking in at five and a half minutes, the video clearly shows the operating principles behind the device.

It starts off with the question, what should you do if you want to drop a voltage? Many of us know that we can dim and brighten an LED using the PWM on an Arduino, but a closer inspection with an oscilloscope still shows 5V peaks that would be dangerous to a 3.3V circuit. He then adds an inductor and diode, this keeps the current from dropping too fast, but the PWM just isn’t switching fast enough to keep the coil energized.

A small modification to the Arduino’s code, and the PWM frequency is now in the kHz range. The voltage looks pretty good on the oscilloscope, but a filter cap gets it to look nice and smooth. Lastly, he shows how when the load changes the voltage out looks different. To fix this a voltage divider feeds back the information to the Arduino, letting it change the PWM duty to match the load.

In the last minute of the video he shows how to hook up off-the-shelf switching regulators, whose support components are now completely demystified as the basic principles are understood. Video after the break.

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Feeding The Cat, Reinventing the Wheel

There are few projects that we see as many iterations of as the pet feeder or the plant waterer. (What is it with you people? Are you all as forgetful as we are?) Still, the fun is in the details of the implementation. Or at least that’s the case with [Emmaanuel]’s cat feeder.

The writeup is split into three parts: the worm-drive, the electronics, and the housing (here in English: worm, electronics, housing). And of course, there’s a video inlined below.

The auger and motor housing make great use of PVC pipe and 3D printing, and the dispenser unit looks quite professional. There’s not all that much to say about the electronics — an Arduino clone, an LCD, and a cheap gear motor do just about what you’d expect.

The CNC’ed case with spring-fit tabs steals the show, however. It’s made out of MDF, which doesn’t take well to screwing or glueing. With carefully routed pins and tabs that have a little spring in them, [Emmaanuel] was able to take the pieces off the mill table and just snap them together. Awesome.

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Field Expedient Bandsaw Mill Deals with Leftover Logs

When a questionable tree threatened his house, [John Heisz] did the sensible thing and called in a professional to bring it down. But with a flair for homebrew tools, [John] followed up with a seemingly non-sensible act and built a quick and dirty DIY bandsaw mill to turn the resulting pile of maple logs into usable lumber.

A proper bandsaw mill is an expensive tool. Prices start in the mid-four figures for a stripped down version and can easily head into the multiple tens of thousands for the serious mills. [John] makes it clear that his mill is purpose-built to deal with his leftover logs, and so he made no attempt at essentials like a way to index the blade vertically. His intention was to shim the logs up an inch after each cut, or trim the legs to move the blade down. He also acknowledges that the 2-HP electric motor is too anemic for the hard maple logs – you can clearly see the blade bogging down in the video below. But the important point here is that [John] was able to hack a quick tool together to deal with an issue, and in the process he learned a lot about the limitations of his design and his choice of materials. That’s not to say that wood is never the right choice for tooling – get a load of all the shop-built tools and jigs in his build videos. A wooden vise? We’d like to see the build log on that.

We’ve featured a surprising number of wooden bandsaws before, from benchtop to full size. We’re pretty sure this is the first one purpose built to mill logs that we’ve featured, although there is this chainsaw mill that looks pretty handy too.

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Beautiful Kegerator, Built the Hard Way

[Luke] brews his own beer. And like all beer brewers, he discovered that the worst part of homebrewing is cleaning out all the bottles. Time for a kegging system! And that means, time for a kegerator to keep the brew cold.

Normal kegerators are just a few holes drilled in an appropriate refrigerator. Most fridges have a step in the back where the compressor lives, which makes kegs an awkward fit, so [Luke] decided to build his own refrigerator.

He used beautiful wood and plenty of insulation. He failed, though, because he succumbed to the lure of the Peltier cooler. If there’s one problem with Peltier projects, it’s building first and looking up the specs second. They never have enough cool-juice. To quote [Luke]:

“… a comment I had seen somewhere on the Internet began to sink in: all projects involving peltier devices ultimately end in disappointment.

(Bolding and italics from the original.) But at least he learned about defrosting, and he had a nice wood-paneled fridge-box in the basement.

Rather than give up, he found a suitable donor fridge, ripped out its guts, and transplanted them into his homemade box. A beautiful tap head sitting on top completes the look. And of course, there’s an ESP8266 inside logging the temperature and controlling the compressor, with all the data pushed out over WiFi. Try doing that with your Faraday Cage metal fridge!

We’ve seen kegerator builds before. Some of our favorites include this one that has a motorized retracting tap tower, and one that’s built into the walls of the house.

DIY PCB Fixture Helps You Spread the Paste

(Yeah, we don’t know what that title means either.) But holding your PCBs down in one place and nicely registered while you spread solder paste over them is a problem that needs solving, and [Carsten] did it nicely.

High volume PCB manufacturers have expensive screen printers to do this. The standard hardware hacker solution is to tape some scrap PCBs of the same thickness down to the table to hold the PCBs solidly in place. But if you’re doing a large run, and if you’re already firing up the laser to cut out mylar stencils, you might as well cut out some PCB-holding fixtures to match.

[Carsten]’s blog entry is short on details, but you get the idea just from looking at the picture, right? Adding registration pins to the holder that engage with the stencils could make this a real time-saver as well. As long as you’re lasering the stencil and the holder, there’s nothing stopping you. It’s a simple idea, but a good one, so we thought we’d share. Our only remaining question: what’s a Karate Light?