If you’ve ever spent any time around a lab, you’ve doubtless seen one of those awesome combination magnetic stirrer and heater plates that scientists use to get liquids mixed and up to temperature. If you’ve ever etched your own PCBs using ammonium persulfate, you’ve experienced the need for both heating and agitation firsthand. Using a stirrer plate for PCB etching is putting two and two together and coming up with four. Which is to say, it’s a good idea that’s not amazingly novel. [acidbourbon] built his own, though, and there’s almost no part of this DIY heater/stirrer that isn’t a hack of some kind or another.
Start off with the temperature controller. Instead of buying a thermocouple or using an LM75 or similar temperature-measurement IC, [acidbourbon] uses a bog-standard 1n4148 diode. The current passed through a diode, at a given voltage, is temperature dependent, which means that adding a resistor and a microcontroller’s ADC yields a quick hacked temperature sensor. [acidbourbon] glued his straight onto the casserole that he uses as an etching tray.
Does the type of person who saves $0.25 by using a diode instead of a temperature sensor go out and buy a stirrer motor? No way. Motor and gears come from a CD-ROM drive. The “fish” — the magnetic bar that spins in the etchant — is made of neodymium magnets lengthened by shrink-wrapping heat-shrinking them together with some capacitors. Who knew that shrinkwrap heat-shrink, fused with pliers, was waterproof? Is that a wall-wart in that box, with the prongs wired to mains electricity?
When you already know exactly where and how you’d like your motor to behave, a code-compile-flash-run-debug cycle can work just fine. But if you want to play around with a stepper motor, there’s nothing like a live interface. [BrendaEM]’s RDL is a generic stepper motor driver environment that you can flash into an Arduino. RDL talks to your computer or cell phone over serial, and can command a stepper-driver IC to move the motor in three modes: rotary, divisions of a circle, and linear. (Hence the acronumical name.) Best of all, the entire system is interactive. Have a peek at the video below.
The software has quite a range of capabilities. Typing “?” gets you a list of commands, typing “@” tells you where the motor thinks it is, and “h” moves the motor back to its home position. Rotating by turns, degrees, or to a particular position are simple. It can also read from an analog joystick, which will control the rotation speed forward and backward in real time.
Division mode carves the pie up into a number of slices, and the motor spins to these particular locations. Twelve, or sixty, divisions gives you a clock, for instance. Acceleration and deceleration profiles are built in, but tweakable. You can change microstepping on the fly, and tweak many parameters of the drive, and then save all of the results to EEPROM. If you’re playing around with a new motor, and don’t know how quickly it can accelerate, or what speeds it’s capable of, nothing beats playing around with it interactively.
Whether you’re lodged in an apartment with a poor view of the sky like [Becky Stern] or are looking for an at-a-glance report of the current weather, you might consider this minimalist weather display instead of checking your computer or your phone every time you’re headed out the door.
The first order of business was to set up her Feather Huzzah ESP8266 module. [Becky] started with a blink test to ensure it was working properly. Once that was out of the way, she moved on to installing a few libraries. Temperature data fetched by an IFTTT feed is displayed on a seven-segment display, while additional feeds separately retrieve information for each basic weather type: sunny, overcast, rain, snow.
All it took to create the sleek display effect was a few pieces of cardboard inside a shadow box frame, a sheet of paper as a diffuser, and twelve Neopixel RGB LEDs hidden inside. Trimming and securing everything in place as well as notching out the back of the frame for the power cable finished the assembly. Check out the build video after the break.
Artist Pe Lang uses linear polarization filters to create an unusual effect in his piece polarization | nº 1. The piece consists of a large number of discs made from polarizing film that partially overlap each other at the edges. Motors turn these discs slowly, and in the process the overlapping portions go from clear to opaque black and back again.
The disc rotation speed may be low but the individual transitions occur quite abruptly. Seeing a large number of the individual discs transitioning in a chaotic pattern — but at a steady rate — is a strange visual effect. About 30 seconds into the video there is a close up, and you can see for yourself that the motors and discs are all moving at a constant rate. Even so, it’s hard to shake the feeling of that one is watching a time-lapse. See for yourself in the video, embedded below.
With almost 8 billion souls to feed and a changing climate to deal with, there’s never been a better time to field a meaningful “Internet of Agriculture.” But the expansive fields that make industrial-scale agriculture feasible work against the deployment of sensors and actuators because of a lack of infrastructure to power and connect everything. So a low-power radio network for soil moisture sensors is certainly a welcome development.
We can think of a lot of ways that sensors could be powered in the field. Solar comes to mind, since good exposure to the sun is usually a prerequisite for any cropland. But in practice, solar has issues, the prime one being that the plants need the sun more, and will quickly shade out low-profile soil-based sensors.
That’s why [Spyros Daskalakis] eschewed PV for his capacitive soil moisture sensors in favor of a backscatter technique very similar to that used in both the Great Seal Bug and mundane RFID tags alike. The soil sensor switches half of an etched PCB bowtie antenna in and out of a circuit at a frequency proportional to soil moisture. A carrier signal from a separate transmitter is reflected off the alternately loaded and unloaded antenna, picking up subcarriers with a frequency proportional to soil moisture. [Spyros] explains more about the sensor design and his technique for handling multiple sensors in his paper.
Stepper motors are a staple in all sorts of projects, but it’s often the case that a gearbox is needed, especially for applications like the linear drives in CNC machines and 3D printers. In those mechanisms, a high-torque, low backlash gearbox might be just the thing, and a 3D printable split planetary harmonic drive for the popular NEMA 17 motors would be even better.
Right up front, we’ll say that we’re skeptical that any plastic gearbox can stay as backlash free as [SirekSBurom] claims his creation is. But we can see the benefits of the design, and it has some nice features. First off, of course, is that it’s entirely 3D printed, except for a few screws. That it mates perfectly with a NEMA 17 motor is a really nice feature, too, and with the design up on Thingiverse it shouldn’t be too tough to scale it up and down accordingly. The videos below show you the theory: the stepper drives a sun gear with two planet gears orbiting, each of which engages a fixed ring of 56 teeth, and an output ring of 58 teeth. Each revolution of the planets around the fixed ring rotates the output ring by one tooth, leading to almost 100:1 reduction.
We think the ‘harmonic’ designation on this gearbox is a little of a misnomer, since the defining feature of a harmonic drive seems to be the periodic deformation of a flex spline, as we saw in this 3D-printed strain wave gear. But we see the resemblance to a harmonic drive, and we’ll admit this beastie is a little hard to hang a name tag on. Whatever you call it, it’s pretty cool and could be a handy tool for all kinds of builds.
Brewing beer or making wine at home isn’t complicated but it does require an attention to detail and a willingness to measure and sanitize things multiple times, particularly when tracking the progress of fermentation. This job has gotten easier thanks to the iSpindel project; an ESP8266 based IoT device intended as a DIY alternative to a costly commercial solution.
Tracking fermentation normally involves a simple yet critical piece of equipment called a hydrometer (shown left), which measures the specific gravity or relative density of a liquid. A hydrometer is used by winemakers and brewers to determine how much sugar remains in a solution, therefore indicating the progress of the fermentation process. Using a hydrometer involves first sanitizing all equipment. Then a sample is taken from the fermenting liquid, put into a tall receptacle, the hydrometer inserted and the result recorded. Then the sample is returned and everything is cleaned. [Editor (and brewer)’s note: The sample is not returned. It’s got all manner of bacteria on/in it. Throw those 20 ml away!] This process is repeated multiple times, sometimes daily. Every time the batch is opened also increases the risk of contamination. Continue reading “IoT Device Pulls Its Weight in Home Brewing”→