Simple Add-On Makes Cheap Plasma Cutter Suitable For CNC Use

September 30, 2023 by Dan Maloney 15 Comments

Plasma cutters are ridiculously cheap these days, just cruise by the usual online sources or your local Harbor Freight if you’ve got any doubt about that. But “cheap” and “good” don’t always intersect on a Venn diagram, and even when they do, not every plasma cutter is suitable for use on the spanking new CNC table you’re building. But luckily, there’s a mod for that.

As [Jake von Slatt] explains it, there are two kinds of plasma cutters on the market: high-frequency (HF) start and pilot arc start. The basic difference is that HF start cutters, which comprise the majority of cheap cutters on the market, need direct electrical contact with the workpiece to start the cutting action. Pilot arc torches, which are more suitable for CNC cutters, can strike the arc through a separate conductor without the need to contact the workpiece.

While there are homebrew bodges that claim to turn an HF torch into a pilot arc, [Jake]’s approach is a bit more complicated, and necessarily so. His add-on box intercepts the ground clamp — which is actually the positive conductor for plasma cutting — and switches it through a heavy-duty HVAC contactor. The 24 VDC coil of the contactor is controlled by a homebrew current sensor made from a huge toroid ferrite core wrapped with 20 turns of 6 AWG welding wire.

Before winding, the core is split in two and epoxied back together with a small magnetic reed switch bridging the gap. A simple 24 VDC power supply runs the whole thing. When the torch starts, the nozzle is connected to ground through the contactor, but as soon as the arc strikes and starts pulling cutting current through that toroid, the magnetic field closes the reed switch, which opens the contactor via a small DC relay. This removes the connection between the nozzle and ground, leaving the plasma to carry all the cutting current.

We’ve featured many, many CNC plasma cutter tables before, but most of these builds have concentrated on the table more than the cutter. It’s a refreshing change to get some insider tips on what kinds of cutters work best, and how to adapt what you’ve got for the job.

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Giant DIY Mouse Sets The Ball Free

January 29, 2021 by Kristina Panos 8 Comments

Make the move to a split keyboard and the first thing you’ll notice is that you have all this real estate between the two halves. (Well, as long as you’re doing it right). This is the perfect place to keep your cat, your coffee cup, or in [Jacek]’s case, your fantastic DIY trackball mouse.

Don’t be fooled by the orange plastic base — all the electronics are rolled up inside that big sexy ball, which [Jacek] printed in two halves and glued together. Inside the ball there’s an Adafruit Feather nRF52840 Sense, which has an onboard accelerometer, gyroscope, and magnetometer. As you’ll see in the video after the break, the Feather takes readings from these and applies a sensor-fusing algorithm to determine the ball’s orientation in 3D space before sending its position to the computer. To send the click events, [Jacek] baked some mouse buttons into the keyboard’s firmware. Among the other Feather sensors is a PDM MEMS microphone, so detecting taps on the ball and translating them to clicks is not out of the question for a future version.

Here comes the really clever part: there are two reed switches inside the ball. One is used as a power switch, and the other is for setting the ‘up’ direction of the trackball. The ball charges wirelessly in a 3D printed base, which also has a small neodymium magnet for activating the reed switches. Check out the demo after the break, which shows [Jacek] putting the trackball through its paces on a mouse accuracy testing program.

If you prefer your DIY trackballs to be more standard looking, click on over to the Ploopy project.

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Arduino Magnetic Board Is Anything But Boring

June 17, 2020 by Kristina Panos 3 Comments

Magnets (especially those ball magnets!) are endlessly fascinating, aren’t they? It’s almost dangerous to combine them with LEDs, because how are you supposed to get anything done with something like [andrei.erdei]’s Arduino Magnetic Board beckoning from beyond your keyboard?

This tons-of-fun board uses ball magnets to light up RGB LEDs as they roll around on the sexy Plexiglas field. Underneath the LED matrix is an orchestra of 36 reed switches — those little glass gas-filled grains of rice with axial leads that snap together or fly apart in the presence of magnetic fields. The LEDs are controlled with an Arduino Pro Mini, and so is the 8Ω speaker for sound effects.

[andrei.erdei] has already developed a few applications for this delightful desk toy, and they’re all on GitHub. There’s a chase game that involves tilting the board to catch the next red dot with the magnet, a light painting game, and a sequencer that mimics the ToneMatrix. Roll past the break to check out the series of short demo videos.

Want to play with reed switches but can’t source any at the moment? You could just make them yourself.

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Never Miss A Doorbell With This Notifier

March 1, 2020 by Jenny List 14 Comments

[PatH] tells us that he tragically missed a craft beer delivery to his home, and vowed never to let this happen again. His problem was that he’d missed the doorbell, resulting in one of those annoying notes from the delivery guy. His solution? An ESP8266-driven doorbell detector, that both sends him an SMS and records each doorbell press to a Google Sheet.

The doorbell detection is surprising but simple and non-intrusive, instead of running a GPIO line through some kind of interface to the button itself he’s added a reed switch to his ESP8266 board and used that to detect the magnetic field of the bell solenoids. It’s a convenient method, but one that only works with an old-style bell.

When the bell rings the magnetic field triggers the reed switch, and in turn the sketch running on the ESP calls out to IFTTT which triggers both an SMS and a write to a Google Sheets document that records each doorbell activation.

The ESP8266 seems to be a popular choice with doorbell automatprs probably because of its built-in networking and low price, but it’s not the only option. This optocoupler-sensed effort for example uses a Particle Xenon.

An ESP32 Clock With A Transforming LED Matrix

October 29, 2019 by Tom Nardi 5 Comments

Over the years we’ve seen countless ways of displaying the current time, and judging by how many new clock projects that hit the tip line, it seems as though there’s no end in sight. Not that we’re complaining, of course. The latest entry into the pantheon of unusual timepieces is this ESP32-powered desk clock from [Alejandro Wurts] that features a folding LED matrix display.

The clock uses eight individual 8 x 8 LED arrays contained in a 3D printed enclosure that hinges in the middle. When opened up the clock has a usable resolution of 8 x 64, and when its folded onto itself the resolution becomes 16 x 32.

This variable physical resolution allows for alternate display modes. When the hardware detects that its been folded into the double-height arrangement, it goes into a so-called “Big Clock” mode that makes it easier to see the time from a distance. But while in single-height mode, there’s more horizontal real estate for adding the current temperature or other custom data. Eventually [Alejandro] wants to use MQTT to push messages to the display, but for now it just shows his name as a placeholder.

The key to the whole project is the hinged enclosure and the reed switch used to detect what position it’s currently in. Beyond that, there’s just an ESP32 an some clever code developed with the help of the MD_Parola library written for MAX7219 and MAX7221 LED matrix controllers. [Alejandro] has published the code for his clock, which should be helpful for anyone who’s suddenly decided that they also need a folding LED matrix in their life.

Now if the ESP32 LED matrix project you have in mind requires full color and high refresh rates, don’t worry, we’ve got a solution for that.
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Custom Rotary Switch Takes A Motor

April 10, 2019 by Al Williams 9 Comments

There are certain challenges we all will have to face sooner or later. Changing a flat tire in the rain, trying to put on a shirt that doesn’t quite fit, or producing a 16 position rotary switch for a replica computer front panel. There was a time when something like this would be a major undertaking, but with the help of a 3D printer [Mike Gardi] was able to build good looking switches that were big enough to be motor driven.

Switches of course are old tech, and there are plenty of ways to make contacts. [Mike] settled on using 16 small magnets and reed switches. This works, but you probably wouldn’t want to use it where the switch might get close to an external magnet. It does however make for a neat assembly without a lot of mechanical work. It also resists wear compared to a brush type arrangement.

The switch is a little large, but it could probably be made smaller with proper contacts. However, you still need at least some magnets to provide the detents without making mechanical changes.

We couldn’t help but think of the homemade rotary switches from the do it yourself computer that used sewing thread spools, wires, and paper clips. It would be fun to revisit that computer with an eye to making things using a 3D printer. We liked the knob, but if you only need a reproduction knob, there are other ways to go.

Maker Faire NY: Getting Physical With Minecraft

September 30, 2018 by Tom Nardi 6 Comments

If you’ve been hanging around Hackaday for a while, you’ve likely seen a few attempts to bridge the real world with the voxel paradise that is Minecraft. In the past, projects have connected physical switches to virtual devices in the game, or took chunks of the game’s blocky landscape and turned it into a 3D printable file. These were interesting enough endeavors, but fairly limited in their scope. They assumed you had an existing world or creation in Minecraft that you wanted to fiddle with in a more natural way, but didn’t do much for actually playing the game.

But “Physical Minecraft” presented at the 2018 World Maker Faire in New York, offered a unique way to bring players a bit closer to their cubic counterparts. Created by [Manav Gagvani], the physical interface has players use a motion detecting wand in combination with an array of miniature Minecraft blocks to build in the virtual world.

The wand even detects various gestures to activate an array of “Spells”, which are effectively automated build commands. For example, pushing the wand forward while making a twisting motion will automatically create a tunnel out of the selected block type. This not only makes building faster in the game, but encourages the player to experiment with different gestures and motions.

A Raspberry Pi 3 runs the game and uses its onboard Bluetooth to communicate with the 3D printed wand, which itself contains a MetaWear wearable sensor board. By capturing his own moves and graphing the resulting data with a spreadsheet, [Manav] was able to boil down complex gestures into an array of integer values which he plugged into his Python code. When the script sees a sequence of values it recognizes, the relevant commands get passed onto the running instance of Minecraft.

You might assume the wand itself is detecting which material block is attached to it, but that bit of magic is actually happening in the base the blocks sit on. Rather than trying to uniquely identify each block with RFID or something along those lines, [Manav] embedded an array of reed switches into the base which are triggered by the presence of the magnet hidden in each block.

These switches are connected directly to the GPIO pins of the Raspberry Pi, and make for a very easy way to determine which block has been removed and installed on the tip of the wand. Things can get tricky if the blocks are put into the wrong positions or more than one block are removed at a time, but for the most part it’s an effective way to tackle the problem without making everything overly complex.

We’ve often talked about how kid’s love for Minecraft has been used as a way of getting them involved in STEM projects, and “Physical Minecraft” was a perfect example. There was a line of young players waiting for their turn on the wand, even though what they were effectively “playing” was the digital equivalent of tossing rocks. [Manav] would hand them the wand and explain the general idea behind his interface, reminding them that the blocks in the game are large and heavy: it’s not enough to just lower the wand, it needs to be flicked with the speed and force appropriate for the hefty objects their digital avatar is moving around.

Getting kids excited about hardware, software, and performing physically demanding activities at the same time is an exceptionally difficult task. Projects like “Physical Minecraft” show there can be more to playing games than mindless button mashing, and represent something of a paradigm shift for how we handle STEM education in an increasingly digital world.