Wideband Woes and the Junkbox Miata

As ever, I am fighting a marginally winning battle against my 1991 Mazda MX-5, and this is the story of how I came to install a wideband oxygen sensor in my Japanese thoroughbred. It came about as part of my ongoing project to build myself a viable racecar, and to figure out why my 1990s Japanese economy car engine runs more like a late 1970s Malaise-era boat anchor.

I’ve always considered myself unlucky. My taste for early 90s metal has meant I’ve never known the loving embrace of OBD-2 diagnostics, and I’ve had to make to do with whatever hokey system was implemented by manufacturers who were just starting to produce reliable fuel injection systems.

Narrowband oxygen sensor voltage output. The output is heavily dependent on sensor temperature and highly non-linear, making these sensors unsuitable for delivering a true AFR reading.

This generally involves putting in a wire jumper somewhere, attaching an LED, and watching it flash out the trouble codes. My Mazda was no exception, and after putting up with a car that was running rich enough to leave soot all over the rear bumper, I had to run the diagnostic.

It turned up three codes – one for the cam angle sensor, and two for the oxygen sensor. Now, a cam angle sensor (CAS) fault will normally prevent the car running at all, so it’s safe to assume that was an intermittent fault to keep an eye on.

The oxygen sensor, however, was clearly in need of attention. Its job is to allow the engine control unit (ECU) to monitor the fuel mixture in the exhaust, and make sure it’s not too rich or too lean. As my car was very obviously running too rich, and the diagnostic codes indicated an oxygen sensor failure, a repair was in order.

I priced up replacement sensors, and a new oxygen sensor could be had for under $100. However, it wasn’t exactly what I wanted, as not all oxygen sensors are created equal. Cars in the 80s and 90s typically shipped from the OEM fitted with what’s called a narrowband oxygen sensor. These almost always consist of a zirconia dioxide cell that outputs a voltage depending on the difference in oxygen concentration between the exhaust gas and the free air. These sensors generally sit at 0.45 V when the fuel mixture is stoichiometric, but rapidly change to 0.1 V in a lean condition and 0.9 V in a rich condition. The response is highly non-linear, and changes greatly with respect to temperature, and thus is only good for telling the ECU if it’s rich or lean, but not by how much. ECUs with narrowband sensors tend to hunt a lot when running in closed loop O2 control – you’ll see an engine at idle hunt either side of the magical 14.7 stoichiometric air fuel ratio, never able to quite dial in on the correct number.

As I intend to switch to an aftermarket ECU in the future, I’ll need to tune the car. This involves making sure the air/fuel ratios (AFRs) are correct, and for that I need to be able to properly measure them. Just knowing whether you’re rich or lean isn’t enough, as often it’s desirable to run the engine intentionally rich or lean at certain engine loads. To get a true AFR reading requires fitting a wideband oxygen sensor. These are a little more complicated.

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InstantCAD Promises Faster Iterative Design

The design process for any product is necessarily an iterative one. Often, a prototype is modelled or built, and changes are made to overcome problems and improve the design. This can be a tedious process, and it’s one that MIT’s CSAIL has sought to speed up with InstantCAD.

The basic idea is integrating analysis tools as a plugin within already existing CAD software. A design can be created, and then parametrically modified, while the analysis updates on screen in a near-live fashion. Imagine modelling a spanner, and then dragging sliders to change things like length and width while watching the stress concentrations change in real time. The tool appears to primarily be using some sort of finite element analysis, though the paper also shows examples of analyzing fluid flows as well.

The software is impressive, however there are caveats. Like any computer analysis, serious verification work must be undertaken to ensure its validity. We suspect that there may be issues with more complex geometries that lead to inaccurate simulation. It’s not the sort of tool you’d use for anything that puts life and limb at risk, but we can see it having great uses for designing basic objects when you want to quickly gain an idea of what sort of effect certain parameter changes will have.

The other main disappointment is that while this tool looks great, it doesn’t appear to be publicly available in any form. Whether this is due to universities and complicated IP requirements or the potential for future commercialization is anyone’s guess. Regardless, you can read the conference paper here or check out the video below. Or you could read up on the applications of finite element analysis to 3D printer slicers, too.

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Dedicated Button for Toggling Screens

Anyone who regularly presents to an audience these days has known the pain of getting one’s laptop to work reliably with projection hardware. It’s all the more fraught with pain when you’re hopping around from venue to venue, trying desperately to get everything functioning on a tight schedule. [Seb] found that the magic keystrokes they used to deal with these issues no longer worked on the Macbook Pro Touchbar, and so a workaround was constructed in hardware.

The build itself is simple – an Adafruit Trinket serves as the brains, with a meaty 12mm tactile button used for input. The Trinket emulates a USB keyboard and sends the Cmd-F1 keypress to the computer when the button is pressed. The button’s even mounted in a tidy deadbugged fashion.

While it’s not at all complicated from a build standpoint, the key to this project is that it’s a great example of using the tools available to solve real-life problems. When you’re in a rush with 300 people waiting for your talk to start, the last thing you need to be worrying about is a configuration issue. [Seb] now has a big red button to mash to get out of trouble and get on with the job at hand. It does recall this much earlier hack for emulating a USB keyboard with an Arduino Uno or Mega. It’s a useful skill to have!

 

Add a Second SD Card to the Pi Zero

The Raspberry Pi Zero is a beautiful piece of hardware, fitting an entire Linux computer into a package the size of a pack of gum (don’t chew it, though). However, this size comes with limited IO options, which can be a complication for some projects. In this case, [Hugatry] wanted extra storage, and devised a smart method to add a second SD card to the Pi Zero.

The problem with the Pi Zero is that with only a single USB port, it’s difficult to add any other storage to the device without making things bulkier with hubs or other work arounds. Additionally, the main SD card can’t be removed while the Pi is running, so it makes sense to add an easy-to-use removable storage option to the Pi Zero.

It’s quite a simple hack – all that’s required to pull it off is a few resistors, an SD card connector, and some jumper wires. With everything hooked up, a small configuration change enables the operating system to recognise the new card.

Overall it’s great to see hacks that add further functionality to an already great platform. If you find it’s not powerful enough, you can always try overclocking one. 

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Why I Got The Job

Hackaday readers are a vast and varied bunch. Some of us would call ourselves engineers or are otherwise employed in some kind of technical role. Others may still be studying to gain the requisite qualifications and are perhaps wondering just how to complete that final leap into the realm of gainful employment. Well, this one’s for you.

What sort of job are you looking for?

You might be a straight, down the lines, petroleum engineering graduate who’s looking to land a job in the oil and gas industry. Conversely, you might be an arts student who’s picked up a few skills with electronics over the years and are keen to gain a position doing grand installation pieces for musuems or corporate clients.

There’s a broad spectrum of jobs out there that require high-level technical skills, and my first piece of advice is that you shouldn’t limit yourself. There are things you can do to keep your options open, even over a long career – these could pay dividends when you’re looking for a seachange.

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Controlling A Micro Helicopter with a PS2 Controller

The Syma S107G is a venerable stalwart of the micro helicopter market. Affordable, robust, and ubiquitous, the S107G relies on infrared to receive its control signals. Emboldened by the prior work of others, [Robert] set out to control his with a Playstation 2 controller.

In this project, [Robert] is standing on the shoulders of giants, so to speak – we’ve seen others reverse engineer the S107G’s communications protocol before. [Robert] combined the efforts of several others to understand how to send commands to the helicopter, including use of two separate channels for controlling two at once.

With the knowledge of the necessary protocols, it’s then a matter of hooking up 3 LEDs in a somewhat unconventional series arrangement with a 9 volt supply, to be switched by an Arduino hooked up to a computer. A Javascript application running on the computer reads the state of a Playstation 2 controller, and spits it out over serial to the Arduino, which flashes the LEDs.

It’s not the neatest, most lightweight way of building a new controller for your remote control toy, but it does show how quickly one can throw together a project in a weekend by combining modern hardware and software tools. Plus, it’s a great learning experience on a platform that’s been experimented with the world over.

Simulating Snakes and Ladders for Fun, Not Profit

A great many of you will remember the game of Snakes and Ladders from your youth. It’s a simple game, which one grows to realise involves absolutely no skill – it’s purely the luck of the dice. [Alex Laratro] noticed that without player decisions to effect the outcome, the game was thus a prime candidate for simulation. 

[Alex] wanted to dive into the question of “Who is winning a game of Snakes and Ladders?” at any given point in the gameplay. A common approach would be to state “whoever is in front”, but the ladders might have something to say about that. [Alex] uses Markov analysis to investigate, coming to some interesting conclusions about how the game works, and how this compares to the design of more complex games like Mario Kart and Power Grid.

Overall, it’s a breakdown of a popular game that’s simple enough to really sink your teeth into, but has some incredibly interesting conclusions that are well worth considering for anyone designing their own board games. We love seeing math applied to novel and fun problems – and it can solve important problems, too.