Don’t Flake on Your Fish—Feed them Automatically

We get it. You love your fish, but they can’t bark or gently nip at your shin flesh to let you know they’re hungry. (And they always kind of look hungry, don’t they?) One day bleeds into the next, and you find yourself wondering if you’ve fed them yet today. Or are you thinking of yesterday? Fish deserve better than that. Why not build them a smart fish feeder?

Domovoy is a completely open-source automatic fish feeder that lets you feed them on a schedule, over Bluetooth, or manually. This simple yet elegant design uses a small stepper motor to drive a 3D-printed auger to deliver the goods. Just open the lid, fill ‘er up with flakes, and program up to four feedings per day through the 3-button and LCD interface. You can even set the dosage, which is measured in complete revolutions of the auger.

It’s built around an ATMega328P, but you’ll have to spin your own board and put the feeder together using his excellent instructions. Hungry to see this feeder in action? Just swim past the break.

Can’t be bothered to feed your fish automatically? Train them to feed themselves.

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Biasing That Transistor: The Emitter Follower

We were musing upon the relative paucity of education with respect to the fundamentals of electronic circuitry with discrete semiconductors, so we thought we’d do something about it. So far we’ve taken a look at the basics of transistor biasing through the common emitter amplifier, then introduced a less common configuration, the common base amplifier. There is a third transistor amplifier configuration, as you might expect for a device that has three terminals: the so-called Common Collector amplifier. You might also know this configuration as the Emitter Follower. It’s called a “follower” because it tracks the input voltage, offering increased current capability and significantly lower output impedance.

The emitter follower circuit
The emitter follower circuit

Just as the common emitter amplifier and common base amplifier each tied those respective transistor terminals to a fixed potential and used the other two terminals as amplifier input and output, so does the common collector circuit. The base forms the input and its bias circuit is identical to that of the common emitter amplifier, but the rest of the circuit differs in that the collector is tied to the positive rail, the emitter forms the output, and there is a load resistor to ground in the emitter circuit.

As with both of the other configurations, the bias is set such that the transistor is turned on and passing a constant current that keeps it in its region of an almost linear relationship between small base current changes and larger collector current changes. With variation of the incoming signal and thus the  base current there is a corresponding change in the collector current dictated by the transistor’s gain, and thus an output voltage is generated across the emitter resistor. Unlike the common emitter amplifier this voltage increases or decreases in step with the input voltage, so the emitter follower is not an inverting amplifier.

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Plant Biology is a Gateway

Too many college students have been subject to teachers’ aids who think they are too clever to be stuck teaching mere underclassmen. For that reason, [The Thought Emporium] is important because he approaches learning with gusto and is always ready to learn something new himself and teach anyone who wants to learn. When he released a video about staining and observing plant samples, he avoided the biggest pitfalls often seen in college or high school labs. Instead of calling out the steps by rote, he walks us through them with useful camera angles and close-ups. Rather than just pointing at a bottle and saying, “the blue one,” he tells us what is inside and why it is essential. Instead of telling us precisely what we need to see to get a passing grade, he lets our minds wonder about what we might see and shows us examples that make the experiment seem exciting. The video can also be seen below the break.

The process of staining can be found in a biology textbook, and some people learn best by reading, but we haven’t read a manual that makes a rudimentary lab seem like the wardrobe to Narnia, so he gets credit for that. Admittedly, you have to handle a wicked sharp razor, and the chance of failure is never zero. In fact, he will tell you, the opportunities to fail are everywhere. The road to science isn’t freshly paved, it needs pavers.

If a biology lab isn’t in your personal budget, a hackerspace may have one or need one. If you are wondering where you’ve heard [The Thought Emporium]’s voice before, it is because he is fighting lactose intolerance like a hacker.

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Slipcasting Resin Prototypes

[Eric Strebel] doesn’t need an introduction anymore. If there is a picture of an elegantly designed part with a professional finish on our pages, there is a good chance he has a hand in it. This time he is sharing his method of making a part which looks like it is blow-molded but it is not. Blow-molded parts have a distinctive look, especially made with a transparent material and [Eric’s] method certainly passes for it. This could upgrade your prototyping game if you need a few custom parts that look like solidified soap bubbles.

Mold making is not covered in this video, which can also be seen below the break, but we can help you out with a tip or two. For demonstration’s sake, we see the creation of a medical part which has some irregular surfaces. Resin is mixed and degassed then rolled around inside the mold. Then, the big reveal, resin is allowed to drain from the mold. Repeat to achieve the desired thickness.

This is a technique adapted from ceramics called slipcasting. For the curious, an elegant ceramic slipcasting video demonstration can be seen below as well. For an added finishing touch, watch how a laquer logo is applied to the finished part; a touch that will move the look of your build beyond that of a slapdash prototype.

More education from this prolific maker can be seen in his video on painting with a professional-looking finish and his tips for working with foam-core.

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One-key Keyboard is Exercise in Sub-millimeter Design

As [Glen] describes it, the only real goal in his decision to design his single-key USB keyboard was to see how small he could build a functional keyboard using a Cherry MX key switch, and every fraction of a millimeter counted. Making a one-key USB keyboard is one thing, but making it from scratch complete with form-fitting enclosure that’s easy to assemble required careful design, and luckily for all of us, [Glen] has documented it wonderfully. (Incidentally, Cherry MX switches come in a variety of qualities and features, the different models being identified by their color. [Glen] is using a Cherry MX Blue, common in keyboards due to its tactile bump and audible click.)

[Glen] steps though the design challenges of making a device where seemingly every detail counts, and explains problems and solutions from beginning to end. A PIC16F1459, a USB micro-B connector, and three capacitors are all that’s needed to implement USB 2.0, but a few other components including LED were added to help things along. The enclosure took some extra care, because not only is it necessary to fit the board and the mounted components, but other design considerations needed to be addressed such as the depth and angle of the countersink for the screws, seating depth and clearance around the USB connector, and taking into account the height of the overmold on the USB cable itself so that the small device actually rests on the enclosure, and not on any part of the cable’s molding. To top it off, it was also necessary to adhere to the some design rules for minimum feature size and wall thicknesses for the enclosure itself, which was SLS 3D printed in nylon.

PCB, enclosure, software, and bill of materials (for single and triple-key versions of the keyboard) are all documented and available in the project’s GitHub repository. [Glen] also highlights the possibility of using a light pipe to redirect the embedded LED to somewhere else on the enclosure; which recalls his earlier work in using 3D printing to make custom LED bar graphs.

ESP Cookbook Goes Beyond Chips and DIPs

Are you putting ESP8266s in all your projects these days, whether they need one or not? We don’t blame you. These boards are cheap, tiny, oh and they have WiFi.

If you want to spend less time writing code and more time blinking RGB LEDs over Wi-Fi, then check out this ESP cookbook over on IO. [Turo Heikkinen] and team are writing a soup-to-nuts guide to these darlings of IoT. The cookbook leads off with pinouts and networking (of course) before moving into more intricate recipes involving popular sensors and displays.

This cookbook is funny, it’s helpful, and it’s really well-organized. We love that they used the details section to create a linked table of contents. The links all drive to a specific Instructions page where each group of code snippets and explanations can be found. It’s still a work in progress, so you might want to follow it for updates. We have a feeling they’re going to expand the dessert section next.

Love the ESP8266, but hate programming them in that wonky form factor? Here’s a handy programming jig you can build.

Pimp My Scope

Most of us have heard some form of the adage, “You can buy cheaper, but you’ll never pay less.” It means that cheaper products ultimately do not stand up to the needs of their superior counterparts. Hackers love to prove this aphorism wrong by applying inexpensive upgrades to inexpensive tools to fill up a feature-rich tool bag. Take [The Thought Emporium] who has upgraded an entry-level microscope into one capable of polarized and dark-field microscopy. You can also see the video after the break.

Functionally, polarized images can reveal hidden features of things like striations in crystals or stress lines in hot glue threads. Dark-field microscopy is like replacing the normally glaring white background with a black background, and we here at Hackaday approve of that décor choice. Polarizing filters sheets are not expensive and installation can be quick, depending on your scope. Adding a dark-field filter could cost as much as a dime.

Like most mods, the greatest investment will be your time. That investment will pay back immediately by familiarizing you with your tools and their workings. In the long-run, you will have a tool with greater power.

Simple mods like the light source can be valuable, but upgrades are not limited to optical scopes, an electron microscope was brought back to life with Arduino

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