If you are building a home shop, it is common to try to get the cheapest gear you can possibly get. However, professionals often look at TCO or total cost of ownership. Buying a cheap car, for example, can cost more in the long run compared to buying an expensive car that requires less maintenance. Most consumers will nod sagely and think of ink jet printers. That $20 printer with the $80 cartridges might not be such a deal after all. [JohnAudioTech] bought a few cheap multimeters and now has problems with each of them. Maybe that $120 meter isn’t such a bad deal, after all.
The problems he’s seen are the same ones we’ve all seen: noisy selector switches, suspect display readings, and worn off lettering. You can see the whole story in the video below.
Continue reading “The True Cost Of Multimeters”
Greenhouses create an artificial climate specifically suited to the plants you want to grow. It’s done by monitoring conditions like temperature and humidity, and making changes using things like vents, fans, irrigation, and lighting fixtures to boost temperature. But how do you know when it’s time to up the humidity, or vent some of the heat building up inside? The easy way is to use the Arduino-powered Norman climate simulator from [934Virginia] which leverages data from different locations or times of year based on NOAA weather data to mimic a particular growing environment.
Norman relies on a simple input of data about the target location, working from coordinates and specified date ranges to return minimum/maximum values for temperature and humidity weather conditions. It makes extensive use of the Dusk2Dawn library, and models other atmospheric conditions using mathematical modeling methods in order to make relatively accurate estimates of the target climate. There are some simulations on the project’s Plotly page which show what this data looks like.
This data is used by [934Virginia’s] Arduino library to compare the difference between your target climate and actual sensor readings in your greenhouse. From there you can make manual changes to the environment, or if you’re luck and already have an Arduino-based greenhouse automation system the climate adjustments can be done automatically. The project is named after Norman Borlaug, a famous soil scientist and someone worth reading about.
Editor’s Note: This article has been rewritten from the original to correct factual errors. The original article incorrectly focused on replicating a climate without the use of sensors. This project does require sensors to compare actual greenhouse conditions to historic climate conditions calculated by the library. We apologize to [934Virginia] for this and thank them for writing in to point out the errors.
Images courtesy of Wikimedia Commons.
Building an electric motor isn’t hard or technically challenging, but these motors have very little in the way of control. A stepper motor is usually employed in applications that need precision, but adding this feature to a motor adds complexity and therefore cost. There is a small $3 stepper motor available, but the downside to this motor is that it’s not exactly the Cadillac of motors, nor was it intended to be. With some coaxing, though, [T-Kuhn] was able to get a lot out of this small, cheap motor.
To test out the motors, [T-Kuhn] built a small robotic arm. He began by programming his own pulse generating algorithm that mimics a sine wave in order to smooth out the movement of the motor. An Arduino isn’t fast enough to do these computations, though, so he upgraded to using the ESP32. He also was able to implement the inverse kinematics on his own. The result of all this work for a specific platform and motor type is a robotic arm that has a very low cost but delivers performance of much more expensive hardware.
The robot arm was built by [T-Kuhn] too, and all of the details on that build, as well as all the schematics and code, are available on the project site if you need a low-cost robot arm or a good stepper motor controller for a low cost. There are many other ways of getting the most out of other types of low-cost motors as well.
Continue reading “Smooth Moves From Cheap Motors”
We’ve noticed waving cats in restaurants and stores for years, but even the happy bobbing of their arm didn’t really catch our attention. Maybe [Josh] had seen a couple more than we have when it occurred to him to take one apart to see how they work. They are designed to run indoors from unreliable light sources and seem to bob along forever. How do the ubiquitous maneki-neko get endless mechanical motion from one tiny solar cell?
Perhaps unsurprisingly given the prevalence and cost of these devices, the answer is quite simple. The key interaction is between a permanent magnet mounted to the end of the waving arm/pendulum and a many-turn wire coil attached to the body. As the magnet swings over the coil, its movement induces a voltage. A small blob of analog circuitry reacts by running current through the coil. The end effect is that it “senses” the magnet passing by and gives it a little push to keep things moving. As long as there is light the circuit can keep pushing and the pendulum swings forever. If it happens to stop a jolt from the coil starts the pendulum swinging and the rest of the circuit takes over again. [Josh] points to a similar circuit with a very nice write up in an issue of Nuts and Volts for more detail.
We’ve covered [Josh]’s toy teardowns before and always find this category of device particularly interesting. Toys and gadgets like the maneki-neko are often governed by razor-thin profit margins and as such must satisfy an extremely challenging intersection of product constraints, combining simple design and fabrication with just enough reliability to not be a complete disappointment.
For more, watch [Josh] describe his method in person after the break, or try flashing his code to an Arduino and make a waving cat of your own.
Continue reading “An Electromagnet Brings Harmony To This Waving Cat”
CubeSats are tiny satellites which tag along as secondary payloads during launches. They have to weigh in at under 1.33 kg, and are often built at low cost. There’s even open source designs for these little spacecrafts. Over 800 CubeSats have been launched over the last few years, with many more launches scheduled in the near future.
[Thomas Cholakov] coupled a homemade cloverleaf antenna to a software-defined radio to track some of these satellites. The antenna is built out of copper-clad wire cut to the correct length to receive 437 MHz signals. Four loops are connected together and terminated to an RF connector.
This homebrew antenna is connected into a RTL-SDR dongle. The dongle picks up the beacon signals sent by the satellites and provides the data to a PC. Due to the motion of the satellites, their beacons can be easily identified by the Doppler shift of the frequency.
[Thomas] uses SDR Console to receive data from the satellites. While the demo only shows basic receiving, much more information on decoding these satellites can be found on the SDR Satellites website.
This looks like a fun weekend project, and probably the cheapest aerospace related project possible. After the break, watch the full video explaining how to build and set up the antenna and dongle.
Continue reading “Tracking CubeSats For $25”
The short answer: something like $200, if your time is worth $0/hour. How is this possible? Cheap kit printers, with laser-cut acrylic frames, but otherwise reasonably solid components. In particular, for this review, an Anet A8. If you’re willing to add a little sweat equity and fix up some of the bugs, an A8 can be turned into a good 3D printer on a shoestring budget.
That said, the A8 is a printer kit, not a printer. You’re going to be responsible for assembly of every last M3 screw, and there are many. Building the thing took me eight or ten hours over three evenings. It’s not rocket surgery, though. There are very accessible videos available online, and a community of people dedicated to turning this box of parts into a great machine. You can do it if you want to.
This article is half how-to guide and half review, and while the fun of a how-to is in the details, the review part is easy enough to sum up: if you want the experience of building a 3D printer, and don’t mind tweaking to get things just right, you should absolutely look into the A8. If you want a backup printer that can print well enough right after assembly, the A8 is a good deal as well; most of the work I’ve put into mine is in chasing perfection. But there are a couple reasons that I’d hesitate to recommend it to a rank beginner, and one of them is fire.
Still, I’ve put 1,615 m (1.0035 miles) of filament through my A8 over 330 hours of run-time spread across the last three months — it’s been actively running for 15% of its lifetime! Some parts have broken, and some have “needed” improving, but basically, it’s been a very functional machine with only three or four hours of unintentional downtime. My expectations going in were naturally fairly low, but the A8 has turned out to be not just a workhorse but also a decent performer, with a little TLC. In short, it’s a hacker’s printer, and I love it.
Continue reading “How Cheap Can A 3D Printer Get? The Anet A8”
If you’ve ever cringed over throwing away any printer filament you know wouldn’t cover your next small part — let alone an overnight print — you may appreciate [starlino]’s method for joining two spools of filament together.
While there are other methods to track how much filament you’re using, this method removes some of the guesswork. First, snip the ends of the filament on a diagonal — as close to the same angle as possible. Cover both ends with shrink wrap tubing — 2mm tubing for 1.75mm filament for example — ensuring that the two ends overlap inside the wrap. Tape the filament to a heat resistant mat with Kapton tape, leaving exposed the joint between the two filaments. A temperature sensor may help you to find your filament’s melting point, or you can experiment as necessary to get a feel for it.
Melt the filament inside the tubing with a hot air soldering station or heat gun and cool it down promptly with a few blasts from an air duster. All that’s left is to cut the filament free of the tape and shrink wrap, scraping away any excess so as to prevent printer jams. Done! Now, back to printing! Check out the tutorial video after the break.nning
Continue reading “Worried About Running Out Of Filament Mid-Print? Join It!”