So, what are you doing for the next five and a half hours? If you’re as busy as we are, you might have to digest this amazing 18 part series of videos over the course of a week or so, but we can almost guarantee you’ll learn a lot. It’s a speedrun through the best collection of Mechanical Engineering knowledge we’ve every come across.
In this epic Youtube video series [Dan Gelbart] shares his knowledge of 40 years of prototyping mechanical designs in a way we’ve never seen before. Not only does he show you how to build things, but he gives away a life time of “tips and tricks” that only a veteran builder would know. There are so many little gems of wisdom in this video series, it’s hard to know where to start with our description. He covers all the usual topics: everything from materials, adhesives, coatings, and such. But the real value of this series is all the little trinkets of information he shares along the way.
Don’t be intimated by some of the tools he’s using – chances are there is a DIY version of the piece of equipment out there, and often you can find a hackerspace or enthusiast in the area who will help you out with their gear. We think this video series should be a must watch for any engineering student or hacker. We made a video playlist for you so you can start watching the videos after the break.
Here’s a quick question: are Geiger and Giger (as in H.R. Giger, designer of the Alien Xenomorph) pronounced the same? The answer is no. Nevertheless, the late artist has had his name mispronounced (for the record, it’s ghee-gur) by many over the years. [Steve DeGroof’s] friend posted a goofy tweet that gave him the inspiration to finally put a skeletal lid on the matter, the Giger Counter.
The innards are a Mightyohm Geiger Counter Kit. The external casing is where the true hack lies in this project, made from a 1:2 scale plastic skeleton model, flexible conduit, and dark metallic spray paint. Only the ribcage, some vertebrae, and part of the skull are used from the model. They are assembled in a delightfully inhuman fashion with some conduit wrapped around it and into the bottom of the ribcage for good measure. After some gluing and spray painting, the LED from the Geiger Counter kit is placed through a drilled hole in the skull while the board sits inside the ribcage. Getting the board in and out can be a little tricky, but it looks like the batteries can be changed without having to pull the whole board out.
Most hobbyists say that it is easier to build a functional prototype of an electronic device, than to make the enclosure for it. You could say that there are a lot of ready-made enclosures on the market, but they are never exactly what you need. You could also use a 3D printer to build a custom enclosure, but high-end 3D printers are too expensive, and the cheaper ones produce housings which are often not robust enough, and also require a lot of additional treatment.
Another way is to build the enclosure out of FR4, a material which is commonly used in PCB production. Such enclosures are low-cost, with thin walls but yet very strong, nice looking, pleasant to the touch and have excellent thermal and moisture stability. FR4 offers some more possibilities – efficient wiring with no wires inside the housing, integrated UHF or SHF antennas or RFID coils, capacitive switches, electrical shielding, selective semi-transparency, water or air tightness, and even integration of complex mechanical assemblies.
Here I shall explain the process of building those “magic” enclosures. It is based on nearly fifty years of personal experience and more than a hundred enclosures, built for most of my projects. Here are two examples – this case for a hardware password manager is just a few centimeters long, while the other one (protective transportation cover for my son’s synthesizer) measures 125cm (about 49 inches), and yet both of them are strong enough to withstand a grown man standing on top of them.
The global approach is simple – you take the sheet of single-sided copper clad FR4, cut it and solder the parts together. That sounds simple, but there are a lot of details which should be met if you want to get top results. Please read about them carefully. You might be tempted to skip some of the steps described here, but if you do so, you will most likely end up being disappointed with the results.
It’s time to do a series on logic including things such as programmable logic, state machines, and the lesser known demons such as switching hazards. It is best to start at the beginning — but even experts will enjoy this refresher and might even learn a trick or two. I’ll start with logic symbols, alternate symbols, small Boolean truth tables and some oddball things that we can do with basic logic. The narrative version is found in the video, with a full reference laid out in the rest of this post.
The most simple piece of logic is inversion; making a high change to low or a low change to high. Shown are a couple of ways to write an inversion including the ubiquitous “bubble” that we can apply almost anywhere to imply an inversion or a “True Low”. If it was a one it is now a zero, where it was a low it is now a high, and where it was true it is now untrue.
Moving on to the AND gate we see a simple truth table, also known as a Boolean Table, where it describes the function of “A AND B”. This is also our first opportunity to see the application of an alternate symbol. In this case a “low OR a low yields a low”
Most if not all of the standard logic blocks come in an inverted form also such as the NAND gate shown here. The ability to invert logic functions is so useful in real life that I probably used at least three times the number of NAND gates as regular AND gates when doing medium or larger system design. The useful inversion can occur as spares or in line with the logic.
A few years ago, [Mitch Altman] from Noisebridge came up with the idea of a Hackerspace Passport. The idea behind it was not to hinder or monitor travels but to encourage visiting other hackerspaces. These passports can be purchased for just a few dollars or, in true open source fashion, be made with nothing more than a computer printer… the Hackerspace Passport design files are totally free and available here.
So next time you’re visiting a new hackerspace, bring your passport and get it stamped to document the trip…. and that brings us to the point of this post: The Stamp. At around $25, having a custom ink stamp made at an office supply store isn’t that much money, but buying a stamp is not as fun as making one! That is what we are going to do today; make a stamp… or more specifically, several stamps using different techniques. Then we’ll compare the performance of each method.
Stamp 3D Model
Inkscape solid HaD logo
Inkscape Lined HaD Logo
Printed Stamp Mold
Printed Stamp STL
Since this is Hackaday, we will be making a Hackaday Logo stamp. Back a couple years ago we ran a contest asking folks to make unique things with the Hackaday logo. To make it easy for the entrants, the Hackaday logo was made available in SVG format. We’ll start with that, since it is available, and make a minor change by adding some lettering, as most soon-to-be stamp makers will probably want letters on their stamps too. This is easily done in the FOSS vector graphic editor software: Inkscape.
The stamp size is important. A Hackerspace Passport page has room for 4 stamps up to 41 x 47mm and we’ll try to keep our stamp within those limits.
A Thermocouple is a terrific way to measure temperature. The effects of temperature change on dissimilar metals produces a measurable voltage. But to make that measurement you need an amplifier circuit designed for the thermocouple being used.
While researching “Zero Drift Amplifiers” as a follow-up to my video on Instrumentation Amplifiers I noticed the little schematic the front page of the LTC1049 datasheet which is shown here. I thought it was an ideal example of an analog application where some gain and some “gain helper” were needed to accomplish our useful little application of amplifying a thermocouple probe.
In the video I don’t really talk much about the thermocouples themselves other than the type I see most of the time which is type K. If you’re not already familiar with the construction of these probes you can find an informative write-up on thermocouples and the different types on the Wikipedia page and you might also want to check out the Analog Devices app note if you would like to know more. What I will cover is a reliable and precise way to read from these probes, seen in the video below and the remainder of the post after the break.
Microcontroller Dev Boards have the main hardware choices already made for you so you can jump right into the prototyping by adding peripherals and writing code. Some of the time they have everything you need, other times you can find your own workarounds, but did you ever try just swapping out components to suit? [Andy Brown] documented his process of transplanting the clock crystal on an STM32F4 Discovery board.
Even if you don’t need to do this for yourself, the rework process he documented in the clip after the break is fun to watch. He starts by cleaning the through-hole joints of the crystal oscillator with isopropyl alcohol and then applies some flux paste to each. From there the rest is all hot air. The crystal nearly falls out due to gravity but at the end he needs to pluck it out with his fingers. We’re happy to see others using this “method” as we always feel like it’s a kludge when we do it. Next he grabs the load caps with a pair of tweezers after the briefest of time under the heat.
We’d like to have a little bit of insight on the parts he replaces and we’re hoping there are a few crystal oscillator experts who can leave a comment below. [Andy] calculates a pair of 30pf load caps for this crystal. We understand the math but he mentions a common value for board and uC input capacitance:
assuming the commonly quoted CP + CI = 6pF
So we asked and [Andy] was kind enough to share his background on the topic:
It’s a general “rule of thumb” for FR4 that the stray capacitance due to the traces on the board and the input (lead) capacitance of the the MCU is in in the range of 4-8pF. I’m used to quoting the two separately (CP,CI) but if you look around you’ll see that most people will combine the two and call it just “CP” and quote a value somewhere between 4 and 8pF. It’s all very “finger in the air” and for general purpose MCU clocks you can get away picking the mid-value and be done with it.
That leaves just one other question; the original discovery board had an in-line resistor on one of the crystal traces which he replaces with a zero ohm jumper. Is it common to include a resistor and what is the purpose for it?