emf

20 Articles

Recreating The “Stuck Throttle” Problem On A Toyota

October 30, 2022 by 68 Comments

A few years ago, Toyota was in the news for a major safety issue with a number of their passenger vehicles. Seemingly at random, certain cars were accelerating without concern for driver input, causing many crashes and at least 37 confirmed deaths. They issued recalls both for the floor mats which were reported to have slid forward to jam the accelerator pedal, but this didn’t explain all of these crashes. There was another recall for stuck throttles, which [Colin O’Flynn] demonstrates a possible cause for on his test bench.

While most passenger vehicles older than about 15-20 years controlled the throttle with a cable connected directly from the throttle body to the accelerator pedal, most manufacturers have switched to a fly-by-wire system which takes sensor input from the accelerator pedal and sends that position information to the vehicle’s computer which in turn adjusts the throttle position. This might be slightly cheaper to manufacture, but introduces a much larger number of failure modes to a critical system. Continue reading “Recreating The “Stuck Throttle” Problem On A Toyota” →

The Hackaday Summer Camp Survival Guide

August 3, 2022 by 19 Comments

It’s a feature of summer for us, the round of hacker camps in which members of our community gather in fields and spend a few days relaxing and doing what we do best. This summer I’ll have been to four of them by September, one of which was unexpected because a last-minute ticket came my way. For Hackaday they’re a chance to connect with our readers and maybe see come of the coolest stuff in person.

If you consult the wiki for your hacker camp of choice then you’ll usually find a page of tips about what to bring. Starting with a tent and a sleeping bag and probably going on to sunscreen, a hat, and maybe how to avoid dehydration. I’d probably add spare toilet paper and disinfectant spray in case the toilets are nightmarish. All very practical stuff, but expressed in a dry list format that doesn’t really tell you what to expect. A hacker camp can be overwhelming if you’ve not been to one before, so how do you get the best out of it? Here are a few tips based on our experience. Continue reading “The Hackaday Summer Camp Survival Guide” →

Badges Of 2022: EMF TiDAL

July 8, 2022 by 5 Comments

As we slowly return to a summer of getting together in fields for our festivals of hackery, it’s time to look at another of this year’s crop of badges. The UK’s Electromagnetic Field, or EMF, is normally a two-yearly event, but its return this year comes after a four year absence due to the pandemic. The EMF 2022 badge is a departure from previous outings, gone is the handheld game console form factor and in its place is a svelte USB-C stick with a nod to the first generation of EMF badges in its wave shape.

The text is a little small on the tiny screen.
On the rear is this pattern.

Physically the badge is formed of two PCBs that plug together with the LiPo battery sandwiched between them, the upper one carrying the display and battery while the lower holds the ESP32-S3 MCU and the various peripherals. These include a QMA7981 accelerometer, a QMC7983 magnetometer, and perhaps most intriguingly, an ATECC108A cryptographic accelerator. This last component gives it the potential to be a 2-factor authentication key, which we think is probably a first for a badge.

In use, the TFT display and joystick interface is usable, but hard to read for a Hackaday scribe whose eyes maybe aren’t as sharp as they used to be. Programming is via MicroPython, using an app format through the same online hatchery system that will be familiar to owners of other European badges. There are already quite a few apps, which we hope will help this badge have some longevity.

This is just the latest of a long line of EMF badges, of which the 2016 version is probably our favourite.

The circuit, assembled on a purple PCB, with a large capacitor and a sizeable white resistor, wires soldered to holes in the PCB

Protect Your Drivers When The Motor Stalls

June 13, 2022 by 46 Comments

[Mark Rehorst] tells us about a tragic incident involving an untimely demise of $200 worth of motor driving hardware, and shares a simple circuit so that we can prevent such tragedies in the future. His Arrakis sand table project has quite a few motors involved, and having forgotten to add limits into the software, he slammed a motor-driven mechanism into a well-fixed part of the table. The back EMF of the motor created a burst of energy, taking out the motor driver, the controller board, and the power supply.

With the postmortem done, he had to prevent this from happening again – preferably, in hardware. Based on a small appnote from Gecko Drives, he designed a simple PCB that shunts the motor with a high-power resistor, as soon as the current starts flowing into a direction it’s not supposed to flow into. He goes in depth about the way that the circuit works and the reasoning behind parts selection, as well as shows an LTSpice simulation and shares the PCB files. This was his first time designing PCBs in KiCad, and we believe he’s done a great job! This worklog is certainly worth reading if you’d like to understand how such circuits work and what goes into building one.

He dubs this a “bank account protection” circuit, and we can absolutely relate. It’s not just CNC tables that need such protections of course – we’ve seen a solution for small hacky makeshift electric vehicles, for instance. A motor’s generative properties aren’t always a problem, however – here’s just one example of a hacker trying to put them to good use.

Continue reading “Protect Your Drivers When The Motor Stalls” →

Looking Forward To EMF Camp: Teasing Us With A Schedule

May 9, 2022 by 5 Comments

As we gear up for a summer in the field, or more accurately in a series of fields, it’s time to turn our attention towards Eastnor Castle in the Western English county of Herefordshire, venue for the upcoming Electromagnetic Field hacker camp. Sadly we’ve got no badge to tease you with, but they’ve released a list of the talks that will fill their schedule. There are so many to choose from, we can only mention a few in this article.

We’ll certainly be taking the time to watch [Russell Couper] describe his electric motorcycle project. He’s no stranger to unusual bike builds, having given us a diesel machine at EMF 2016. Then of course there’s our own [Dave Rountree], who will be hacking the radio spectrum with GNU Radio. Sure to be an interesting talk.

One feature of this camp we’re very interested in will be CuTEL, a wired copper telephone network on the field. We’ll be taking along our trusty GPO 746 to be part of it of course, but for those without one, there’s [Matthew Harrold]’s talk on building a copper telephone network in a field.

Our cursory scan of the list finishes up with [Alistair MacDonald] on how not to start a hackerspace. We’ve seen our fair share of hackerspace drama over the years, so whether this one causes pain for ex-hackerspace-directors or not, it promises to be informative for anyone in the hackerspace world.

At the time of writing there are still some EMF tickets for sale, so if the beginning of your June is free we can heartily recommend it. To get a flavour of the event, read our 2018 review.

DIY Machine Enables PEMF Therapy On A Budget

August 29, 2021 by 40 Comments

We’re certainly not qualified to say whether or not pulsed electromagnetic field (PEMF) therapy will actually reduce your stress or improve your circulation, but there seems to be enough legitimate research going on out there that it might be worth a shot. After all, unless you’ve got a pacemaker or other medical implant, it seems pretty unlikely a magnetic field is going to make anything worse. Unfortunately commercial PEMF machines can cost thousands of dollars, making it a fairly expensive gamble.

But what if you could build one for as little as $10 USD? That’s the idea behind the simple DIY PEMF machine [mircemk] has been working on, and judging by its ability to launch bits of metal in the video below, we’re pretty confident it’s indeed producing a fairly powerful electromagnetic field. Even if it doesn’t cure what ails you, it should make an interesting conversation piece around the hackerspace.

While the outside of the machine might look a bit imposing, the internals really are exceptionally straightforward. There’s an old laptop power supply providing 19 VDC, a dual-MOSFET board, a potentiometer, and a simple signal generator. The pulses from the signal generator trip the MOSFET, which in turn dumps the output of the laptop power supply into a user-wound coil. [mircemk] has a 17 cm (6.7 inch) open air version wrapped with 200 turns of copper wire used for treating wide areas, and an 8 cm (3 inch) diameter version with 300 windings for when you need more targeted energy.

Some skepticism is always in order with these sort of medicinal claims, but commercial PEMF machines do get prescribed to users to help promote bone growth and healing, so the concept itself is perhaps not as outlandish as it might seem.

Continue reading “DIY Machine Enables PEMF Therapy On A Budget” →

A Crust-Cutting, Carrot-Chopping Robot

November 30, 2020 by 9 Comments

[3DprintedLife] sure does hate bread crust. Not the upper portion of homemade bread, mind you — just that nasty stuff around the edges of store-bought loaves. Several dozen hours of CAD later, [3DprintedLife] had themselves a crust-cutting robot that also chops vegetables.

This De-Cruster 9000 is essentially a 2-axis robotic guillotine over a turntable. It uses a Raspberry Pi 4 and OpenCV to seek and destroy bread crusts with a dull dollar store knife. Aside from the compact design, our favorite part has to be the firmware limit switches baked into the custom control board. The stepper drivers have this fancy feature called StallGuard™ that constantly reads the back EMF to determine the load the motor is under. If you have it flag you right before the motor hits the end of the rail and stalls, bam, you have a firmware limit switch. Watch it remove crusts and chop a lot of carrots with faces after the break.

This is far from the dangerous-looking robot we’ve seen lately. Remember this hair-cutting contraption?

Continue reading “A Crust-Cutting, Carrot-Chopping Robot” →