A DIY Electronic Load With A Twist

June 6, 2020 by Tom Nardi 13 Comments

If you’re testing a power supply or battery pack, an electronic load is a nice tool to have. By watching the voltage as you crank up the resistance, you can verify the unit’s real-world capabilities quickly and easily. But [Xavier Bourlot] wanted a bit more information than is generally afforded by these devices, so he came up with his own scratch built load that can measure the voltage at multiple points in the circuit.

Now at first glance, it might not be obvious why you’d want such a capability. But [Xavier] is looking to do something very specific with this device: analyze the efficiency of DC-DC converters. The idea is that if the electronic load can measure the voltage on both sides of the converter, it can calculate what kind of losses are being incurred.

Could you do this with a multimeter and a traditional electronic load? Sure. But if it’s the kind of thing you’ll be doing a lot of, it’s not hard to see why this method would be preferable.

But even if you ignore the converter analysis capabilities, this looks to be a very useful device to have around the lab. [Xavier] says it can sink more than 5 amps, and handle an input voltage as high as 100 volts. Powered by an ATmega328P, the load is also fully programmable and even features an I2C expansion port that you can use to hang additional hardware or sensors on. The stock firmware is already quite capable, and the list of future enhancements has some very interesting entries such as the ability to log data over serial or to a SD card.

We’ve seen a number of programmable electronic load projects over the years, ranging from Arduino shields to VFD equipped units that would be the pride of any hacker’s bench.

Vacuum Dust Collection With Self-Powered Relays

June 6, 2020 by Tom Nardi 22 Comments

Like many people with multiple woodworking tools, [Will Stone] wanted to create a centralized dust collection system. But he quickly found that the devil was in the details, as he struggled to find an economic way to automatically kick on the vacuum when one of the tools started up. His final solution might be one of the most elegant, and surely the cheapest, we’ve ever come across.

As with other DIY systems we’ve seen over the years, [Will] is using a simple inductive current sensor to detect when AC power is being drawn by one of his tools. But where the similarity stops is that there’s nothing so pedestrian as a microcontroller reading the output of the sensor. He realized that when the coils in the sensor were energized they were putting out about 7 volts AC, which should be more than enough to trigger a relay.

So he threw together a rectifier circuit on a piece of perfboard, using four LEDs in true hacker style. With the addition of a capacitor to smooth out the voltage, this little circuit is able to trip the 40 amp solid state relay controlling power to the vacuum using nothing more than the energy harvested from the sensor’s coil.

Using a current sensor is great when the tools are close enough to all be plugged into the same line, but that doesn’t help the folks with cordless tools or supersized shops. In that case, you might need to look into a sound-activated system.

Homebrew Coil Winder Makes Toroids A Snap To Wind

June 5, 2020 by Dan Maloney 13 Comments

Anyone who has ever wound a toroidal coil by hand can tell you that it’s not exactly a fun job. Even with the kinds of coils used in chokes and transformers for ham radio, which generally have relatively few windings, passing all that wire through the toroid time after time is a pain. And woe unto anyone who guesses wrong on how much wire the job will take.

To solve those problems, [Sandeep] came up with this clever and effective toroid winder. The idea is to pass a small spool of magnet wire through the toroid’s core while simultaneously rotating the toroid to spread the windings out as evenly as possible. That obviously requires a winding ring that can be opened up to allow the toroid form to be inserted; [Sandeep] chose to make his winding ring out of plywood with a slit in it. Carrying the wire spool, the winding ring rotates on a C-shaped fixture that brackets the toroid, which itself rotates under stepper motor control on a trio of rollers. An Arduino controls the rotation of both motors, controlling the number of windings and their spread on the form. lacking a ferrite core for testing, [Sandeep] used a plywood ring as a stand-in, but the results are satisfying enough to make any manual coil-winder envious.

We love tools like this that make a boring job a snap. Whether it’s cutting wires for wiring harnesses or winding guitar pickups, tools like these are well worth the time spent to build them. But we suppose when it comes to toroid winding, one could always cheat.

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CNC Scroll Saw Makes Promising First Cuts

June 4, 2020 by Tom Nardi 41 Comments

When we talk about CNC machines, we almost invariably mean a computer controlled router. Naturally you can do other forms of automated cutting, say using a laser or a water jet, but what about adding computer control to other types of saws? [Andrew Consroe] recently put together a postmortem video about this experimental CNC scroll saw. While he never quite got it working reliably, we think his approach is absolutely fascinating and hope this isn’t the last we see of the idea.

Those who’ve used a scroll saw in the past might immediately see the challenge of this build: while a router bit or laser beam can cut in any direction, a scroll saw blade can only cut in one. If you tried to make a sharp turn on a scroll saw, you’ll just snap the fragile blade right off. To work around this limitation, [Andrew] came up with the brilliant rotary table that can be seen in the video after the break.

By combining motion of the gantry with table rotation, he’s able to keep the blade from ever making too tight a turn. Or at least, that’s the theory. While the machine works well enough with a marker mounted in place of the blade, [Andrew] says he never got it to the point it could reliably make cuts. It sounds like positioning errors would compound until the machine ended up moving the work piece in such a way that would snap the blade. Still, the concept definitely works; towards the end of the video he shows off a couple of pieces that were successfully cut on his machine before it threw the blade.

While we’ve actually seen DIY scroll saws in the past, this is the first computer controlled one to ever grace the pages of Hackaday. While some will no doubt argue that there’s no sense building one of these now that laser cutters have reached affordable prices, we absolutely love this design and how much thought went into it. At the very least, we figure this it the beefiest doodle-drawing robot ever constructed. Continue reading “CNC Scroll Saw Makes Promising First Cuts” →

RC Lawn Mower Keeps The Grass Greener On Your Side Of The Fence

June 1, 2020 by Sven Gregori 23 Comments

For some people, mowing the lawn is a dreaded chore that leads to thoughts of pouring a concrete slab over the yard and painting it green. Others see it as the perfect occasion to spend a sunny afternoon outside. And then there are those without the luxury of having a preference on the subject in the first place. [elliotmade] for example has a friend who’s sitting in a wheelchair, and would normally have to rely on others to maintain his lawn and form an opinion on the enjoyability of the task. So to retain his friend’s independence, he decided to build him a remote-controlled lawn mower.

After putting together an initial proof of concept that’s been successfully in use for a few years now, [elliotmade] saw some room for improvement and thought it was time for an upgrade. Liberating the drive section of an electric wheelchair, he welded a frame around it to house the battery and the mower itself, and added an alternator to charge the battery directly from the mower’s engine. An RC receiver that connects to the motor driver is controlled by an Arduino, as well as a pair of relays to switch both the ignition and an electric starter that eliminates the need for cord pulling. Topping it off with a camera, the garden chores are now comfortably tackled from a distance, without any issues of depth perception.

Remote-controlling a sharp-bladed machine most certainly requires a few additional safety considerations, and it seems that [elliotmade] thought this out pretty well, so failure on any of the involved parts won’t have fatal consequences. However, judging from the demo video embedded after break, the garden in question might not be the best environment to turn this into a GPS-assisted, autonomous mower in the future. But then again, RC vehicles are fun as they are, regardless of their shape or size.

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Why Does Solder Smoke Always Find Your Face?

June 1, 2020 by Jenny List 38 Comments

For some of us the smell of rosin soldering flux vaporizing from the tip of an iron as a project takes shape is as evocative as the scent of a rose on a summer’s day. We’ve certainly breathed enough of it over the years, as it invariably goes from the piece of work directly into the face of the person doing the soldering. This is something that has evidently troubled [AlphaPhoenix], who has gone to extravagant lengths to research the problem using planar laser illumination and a home-made (and possibly hazardous) smoke generator.

He starts with a variety of hypotheses with everything from a human-heat-driven air vortex to the Coandă effect, but draws a blank with each one as he models them using cardboard cut-outs and boxes as well as himself. Finally he has the light bulb moment and discovers that the key to the mystery lies in his arms coming across the bench to hold both iron and solder. They close off an area of lower-pressure dead space which draws the air current containing the smoke towards it, and straight into his face. It’s something that can be combated with a small fan or perhaps a fume extractor, as despite some video trickery we have yet to master soldering iron telekinesis.

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A Home Made Dumper You’d Swear Came From A Factory

June 1, 2020 by Jenny List 9 Comments

When it comes to YouTube videos, there’s little we like more than some good quality workshop action, watching someone in command of their tools craft a machine from raw materials with an amazing result. It’s something [Workshop From Scratch] delivers with his homemade mini dumper, in which he makes a small dump-truck from scratch with a result that looks as though he’d bought it factory-made from his agricultural supplier.

At its heart is a substantial chassis made from welded together double box section tube, to which he’s bolted a second-hand hydraulic transmission of the type you would find on larger walk-behind groundskeeping machinery. At the back is a front steering axle from a mobility scooter, that pivots on a bearing and wheel hub from a Ford Mondeo to ensure stability on rough ground. There is a platform for the operator to stand on as the little Honda 4-stroke engine moves it around. The bucket is plasma cut and welded, and it’s safe to say that his welding ability exceeds ours.

The result is a machine that looks to be very useful, and dare we admit it, one we wouldn’t mind having a go on. It may not be as powerful as this electric home-built dump truck, but we like it.

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