Author: Jenny List

3428 Articles

Stealing RAM For A Microcontroller From A TFT Display

May 21, 2020 by 12 Comments

PC users with long memories will recall the days when the one-megabyte barrier was  a significant problem, and the various tricks of extended and expanded memory used to mitigate it. One of them was to install a driver that mapped surplus graphics card memory as system memory when the display was in DOS text mode, and it was this that was brought to mind when we read about [Frank D]’s microcontroller implementation of Conway’s Game Of Life.

The components were those he had to hand; an STM32F030F4P6 and an RM68130 176 × 220 TFT board. The STM is not the most powerful of chips, with only 16 kB of Flash and 4 kB of RAM. The display has enough on-board memory to support 18 bits of colour information, but when it is running in eight-colour mode it only uses three of them. The 15 bits that remain are thus available to be used for other purposes, and though the arcane format in which they are read required some understanding they could be used to provide a very useful extra 38720 bytes of RAM for the microcontroller just as once happened with those DOS PC graphics cards of old. Interestingly, the same technique should work with other similar displays.

Though this isn’t a new technique by any means we can’t recall seeing it used in a microcontroller project such as this one before. We’ve brought you many Games of Life though, as well as marking John Conway’s passing earlier this year.

Continue reading “Stealing RAM For A Microcontroller From A TFT Display” →

Don’t Worry, This Box Will Protect You From 5G!

May 21, 2020 by 128 Comments

As part of an investigation into opposition to 5G mobile phone networks in the English town of Glastonbury the BBC reporter [Rory Cellan-Jones] shared details of a so-called 5G protection device that was advertised as casting a bubble of 5G-free space around its owner. This set [The Quackometer] writing, because as part of his probing into the world of snake-oil, he’s bought just such a unit and subjected it to a teardown.

What he has is a plastic project box with a graphic on top, a switch and green LED on the side, and a battery compartment on its rear. Opening the battery compartment reveals a standard 9 V alkaline cell, but the real interest comes when the cover is removed. There is a copper cylinder with a coil of wire round it, though the wires from the coil to the battery have been cut. The active part of the device is simply a battery powering an LED through a switch, as he puts it the device is a £50 ($61) poor quality torch (flashlight). Of more interest is the copper cylinder, which he identifies as a short piece of copper water pipe with two end caps. He doesn’t open it up, leaving us to expect that whatever mystical component deals with the RF must be concealed within it. This is not the usual Hackaday fare, but we know our readers are fascinated by all new technologies and will provide plenty of speculation as to how it might work in the comments.

The BBC story is worth a read to give a little background. If you are a non-Brit and you have heard of Glastonbury it is probably for the famous summer music festival held on a neighbouring farm, but the town is also famous for its connections with Arthurian legend and in recent decades for having become a centre for New Age mysticism. It has also become something of a hotbed of activism against the spread of 5G mobile networks, and has made the news this week because of concerns over the impartiality of a report condemning the technology released by its local government. If you have an interest in the 5G saga then brace yourselves for this document being used to lend a veneer of official credibility.

We’ve spent a while covering 5G issues, and given that some aspects of the story are shaping up to be a gift to technical journalists that keeps on giving, no doubt we’ll bring you more in due course. Devices such as the one featured here could even supplant audiophile products as a source of technical wonderment!

Thanks [Deus Ex Silicium] for the tip.

Look Ma, No Support For My Floating Holes!

May 17, 2020 by 21 Comments

Do you find supports to be annoying, when you use a 3D printer? A lot of time breaking away surplus pieces of plastic and then cleaning up the resulting ragged edges on your prints is certainly an unwelcome chore. But printing in free space is beyond the capabilities of even the most expensive printer, so it seems we’re stuck with supports for the foreseeable future. [Adam Haile] may have a solution to some support woes though, in the form of a clever technique for printing inset holes without support. His designs have a significant quantity of screw holes with inset heads, too far for the printer to bridge over so his technique breaks down the bridge into manageable smaller distances.

In the video below the break he shows how its done, with successive single layers that contain polygons bridging chords across the circle, with each layer approximating further to the final hole and the last holding the hole itself. Over a few layers the hole is created, without any support but with the minor inconvenience of a not perfectly flat inset. It’s a very clever idea, and one that we’d be interested to see further expanded upon by others.

Continue reading “Look Ma, No Support For My Floating Holes!” →

Ultra-Cheap Microcontroller Powers Addressable 7-segment Display

May 16, 2020 by 35 Comments

Since their being revealed to our community over a year ago, the various ultra-cheap microcontrollers in the sub-ten-cent price range have attracted a lot of interest but not so many projects. Their slightly annoying programming and PIC12-derived architectures present a barrier not mitigated by their price, when picking up an Atmel or other processor represents a much easier choice. That’s not to say that they aren’t slowly making an appearance though, and a cracking example comes from [Tim], who’s used a Padauk microcontroller to make an addressable 7-segment display. If you’re used to addressable multi-colour LEDs, this extends the idea into the world of numerical information.

The result is a PCB little bigger than the 7-segment display it serves, with interlocking 0.1″ pin connectors allowing daisy-chaining of modules. The extreme low cost of the parts makes it an attractive solution. Software wise it’s driven in a similar manner to addressable LEDs, and he goes into significant detail on its protocol. The firmware can be found in a GitHub repository. He directs readers to the Easy PDK programmer and the Small Device C compiler, which should be of interest to anyone tempted by these processors.

A Pulse Oximeter From Very Little

May 16, 2020 by 31 Comments

Against the backdrop of a global respiratory virus pandemic, it’s likely that more than a few readers have been thinking about pulse oximeters. You may even have looked at one closely and seen that it’s little more than a device which shines light through your finger, and wondered how they work. It’s something [Giulio Pons] has done, and to show us how it’s done he’s created a working pulse oximeter of his own.

He started with an infra-red heartbeat sensor module, which is revealed as nothing more than an IR LED and a photodiode. Sampling the output from the photodiode allows measurement of heartbeat, but gives not clue as to oxygen saturation. The interesting part comes via the property of red light in that it’s transmission through flesh varies with oxygen saturation, so adding a red LED and alternately measuring from the IR and red illuminations allows a saturation figure to be derived.

Commercial pulse oximeters are pretty cheap, so many of us will no doubt simply order one from the usual sources and call it good. But it’s always interesting to know how any device works, and this project reveals something simpler than we might have expected. If pulse oximeters interest you, compare it with this one we featured a few years ago.

The 19th Century, When Gravity Battery Meant Something Different

May 16, 2020 by 19 Comments

The internet is full of dubious content promoting “free energy” devices and other ideas that stretch credibility, so [Robert Murray-Smith] prefaces his demonstration of a gravity battery with a warning to look elsewhere if you are in search of such things. Instead he’s showing us a pair of cells from The Model Engineer and Amateur Electrician, a printed periodical that sounds to us something like an equivalent of Hackaday from the 1890s. (Video embedded below.)

The cells are termed gravity batteries because their constituents settle out into layers not unlike a tequila sunrise under the influence of gravity, something that made them especially suitable for the home constructor in the late 19th century when there were no handy wall outlets from which to snag a bit of power.

The chemistry of each is not unexpected if you spent any time in your high school’s lab, a zinc-copper primary cell with a zinc sulphate/copper sulphate electrolyte and a secondary zinc-carbon cell with a zinc bromide electrolyte and a layer of bromine forming on charging. The construction in large glass vessels is archaic though, and it’s this that’s prompted his video. He poses the question whether this type of cell might be revived using 21st century techniques to produce something of use today. The video is below the break, and even if you are not about to try your hand at electrochemistry it’s an interesting watch.

Thanks [Blaubär] for the tip! Continue reading “The 19th Century, When Gravity Battery Meant Something Different” →

Electric Vehicles Continue The Same Wasteful Mistakes That Limit Longevity

May 15, 2020 by 372 Comments

A while back, I sat in the newish electric car that was the pride and joy of a friend of mine, and had what was at the time an odd experience. Instead of getting in, turning the key, and driving off, the car instead had to boot up.

The feeling was of a piece of software rather than a piece of hardware, and there was a tangible wait before the start button could be pressed. It was a miracle of technology that could travel smoothly and quietly for all but the longest journeys I could possibly throw at it on relative pennies-worth of electricity, but I hated it. As a technologist and car enthusiast, I should be all over these types of motor vehicles. I live for new technology and I lust after its latest incarnations in many fields including automobiles.

I want my next car to have an electric motor, I want it to push the boundaries of what is capable with a battery and I want it to be an automotive tour de force. The switch to electric cars represents an opportunity like no other to deliver a new type of car that doesn’t carry the baggage of what has gone before, but in that car I saw a future in which they were going badly astray.

I don’t want my next vehicle to be a car like my friend’s one, and to understand why that is the case it’s worth going back a few decades to the cars my parents drove back when when jumpers were goalposts, and the home computer was just a gleam in the eye of a few long-haired outsiders in California.

Continue reading “Electric Vehicles Continue The Same Wasteful Mistakes That Limit Longevity” →