A Scratch-Built Forgotten Classic Of The Early PC Age

All the retrocomputer love for Commodore machines seems to fall on the C64 and Amiga, with a little sprinkling left over for the VIC-20. Those machines were truly wonderful, but what about the Commodore machine that paved their way? What about the machine that was one of the first to be gobbled up in the late 1970s by school districts eager to convert a broom closet into the new “computer lab”?

The PET 2001 might be a little hard to fall in love with given its all-in-one monitor, cassette recorder, and horrible chiclet keyboard, but some still hold a torch for it. [Glen] obviously felt strongly enough about the machine to build a PET from current production parts, and the results are pretty neat. When trying to recreate a 40-year old machine from scratch, some concessions must be made, of course. The case doesn’t attempt to replicate the all-in-one design, and the original keyboard was mercifully replaced by a standard PS/2 keyboard. But other than that the architecture is faithfully replicated using new production 65xx chips and 74HCT family logic chips. [Glen] had to jump through some hoops to get there, but as the video below shows, the finished machine plays a decent game of Space Invaders.

We’ve seen a PET brought back from the grave by FPGA and a C64 emulated on a Raspberry Pi, but going back to basics and building this from scratch was a fitting homage to an important machine in PC history.

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Eyes On The Prize Of Glucose Monitoring

People with diabetes have to monitor their blood regularly, and this should not be a shock to anyone, but unless you are in the trenches you may not have an appreciation for exactly what that entails and how awful it can be. To give a quick idea, some diabetics risk entering a coma or shock because drawing blood is painful or impractical at the moment. The holy grail of current research is to create a continuous monitor which doesn’t break the skin and can be used at home. Unaided monitoring is also needed to control automatic insulin pumps.

Alphabet, the parent company of Google, gave up where Noviosense, a Netherlands company owned by [Dr. Christopher Wilson], may gain some footing. Instead of contact lenses which can alter the flow of fluids across the eye, Noviosense places their sensor below the lower eyelid. Fluids here flow regardless of emotion or pain, so the readings correspond to the current glucose level. Traditionally, glucose levels are taken through blood or interstitial fluid, aka tissue fluid. Blood readings are the most accurate but the interstitial fluid is solid enough to gauge the need for insulin injection, and the initial trial under the eyelid showed readings on par with the interstitial measurements.

Hackers are not taking diabetes lying down, some are developing their own insulin and others are building an electronic pancreas.

Via IEEE Spectrum.

Spend All Day On The Lake

Solar vehicles are getting more and more common as the price of solar panels comes down, and the availability of motors and controllers for all of these vehicles rises. Making a solar-electric bike from a kit is one thing, but this solar-powered boat is a master class in hacking at all levels, from the solar drive train to the pontoons, and even the anchor.

[J Mantzel] has many videos about his boat on his channel, and watching them all will likely leave you wanting to build your own. He builds almost everything on his boat from scratch from things he has lying around. For example, the anchor was hand-built from fiberglass and then filled with concrete, and his steering system is a semi-complex system of ropes, pulleys, and shafts. Most of the boat’s shell was hand-built from fiberglass as well, and everything that can be repurposed is saved for later use.

The ten panels, batteries, inverter, and other miscellaneous part of the system were about half of the cost of the whole vessel, but he reports that he also uses the boat as a backup power source for his house, and can use the system to run other things like an electric chainsaw for example. He also uses the boat for camping and construction, and without having to worry about fuel it has been very useful to him.

If you get into the videos on the channel, you’ll find that this isn’t his only solar-powered boat. He recently completed a solar speedboat as well with a custom-built propeller that can really move across the water. His videos are apparently very popular as well, since they have been linked to repeatedly by readers in some of the recent solar vehicle write-ups we’ve published.

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Fan-Based Parts Tumbler Is A Breeze To Build

A parts tumbler is a great tool to have around. But if you don’t use it all the time, it’s hard to justify dropping hundreds of dollars on one. Fortunately, there are many ways to make your own tumbler while tailoring it to meet the need. Because really, as long as you get the medium moving enough to abrade the parts, you’re good.

[Daniele]’s parts tumbler is cool because it’s fairly easy to make, it’s really quiet, and it does the job quickly. This tumbler moves the medium by using an imbalanced plastic fan, which [Daniele] created by drilling a hole through one of the blades and fastening a short bolt and nut through it. If you’ve ever tried to stop a washing machine from walking away, you may be thinking this is a strange idea, because now he’s got a 4500 RPM vibration machine scuttling about the shop. So really, the true genius of this build lies in the great pains [Daniele] took to absorb all that vibration.

He’s got the fan float-mounted on rubber-lined springs and rubber mats under the washers involved in connecting the latching plastic box to the fan. Our favorite anti-vibration features are the twist-lock power connector and the custom silicone feet made from Motorsil D and cap bolts. We don’t know what the medium is here, but it’s got us thinking Grape-Nuts might work. Blow past the break to chew on the build video.

The only problem with this build is that this type of fan isn’t cheap, and using it this way will definitely shorten its life.

Not a fan of this type of tumbling? Here’s one that takes your drill for a spin.

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Mechanizing A Eurorack Sequencer

Eurorack has taken over the synthesizer community, and hundreds of people are building their own eurorack modules. [Michael Forrest] designed and built his own Eurorack sequencer module that doesn’t use weird things like capacitors and chips to store a signal. Instead, he’s doing it with stepper motors and some clever engineering.

The basic idea of a Eurorack sequencer is to somehow store a series of values and play them back repeatedly. Connect that sequence to a clock, and you get the same pattern of sounds out of your synth. This can be done digitally with a circular buffer, in the analog domain with a bunch of FETs and caps, or in this case, on a piece of paper glued to a stepper motor.

The key bit of mechanism for this build is a stepper motor with 96 steps per rotation. This is important, because the module is controlled by a clock pulse from the sequencer. Since 96 is evenly divisible by 8 and 16, that means this sequencer will play back in 4/4 time. That NEMA 17 motor with 200 steps per resolution simply won’t work in this situation. Rather, it will technically work, but it’ll be unusable.

The electronics for this build are surprisingly simple, with an Arduino taking in the clock pulse and sending the step signals to an H-driver. The motor spins a paper disk, which is read with a photoresistor and a LED. It’s simple enough to be fun, and yes, it is mounted to a proper Eurorack-sized panel. You can check out the video of this build below.

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Fail of the Week: A Candle Caused Browns Ferry Nuclear Incident

A colleague of mine used to say he juggled a lot of balls; steel balls, plastic balls, glass balls, and paper balls. The trick was not to drop the glass balls. How do you know which is which? For example, suppose you were tasked with making sure a nuclear power plant was safe. What would be important? A fail-safe way to drop the control rods into the pile, maybe? A thick containment wall? Two loops of cooling so that only the inner loop gets radioactive? I’m not a nuclear engineer, so I don’t know, but ensuring electricians at a nuclear plant aren’t using open flames wouldn’t be high on my list of concerns. You might think that’s really obvious, but it turns out if you look at history that was a glass ball that got dropped.

In the 1960s and 70s, there was a lot of optimism in the United States about nuclear power. Browns Ferry — a Tennessee Valley Authority (TVA) nuclear plant — broke ground in 1966 on two plants. Unit 1 began operations in 1974, and Unit 2 the following year. By 1975, the two units were producing about 2,200 megawatts of electricity.

That same year, an electrical inspector and an electrician were checking for air leaks in the spreading room — a space where control cables split to go to the two different units from a single control room.  To find the air drafts they used a lit candle and would observe the flame as it was sucked in with the draft. In the process, they accidentally started a fire that nearly led to a massive nuclear disaster.

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Solar Heart Engineered to Beat for Decades

It’s often said that if something is worth doing it’s worth doing right, or maybe even worth overdoing. This is clearly a concept that [ANTALIFE] takes very seriously, as made abundantly clear by projects like the solar powered “beating” heart he made as a gift for his wife. What for most of us would have ended up being a junk bin build becomes a considerable engineering project in his hands, with a level of research and fine tuning that’s frankly staggering.

But [ANTALIFE] didn’t put this much thought into the device just for fun. He wants it to remain functional for as long as 30 years, and hopes he and the missus can still look on it fondly in their retirement years. Keeping an electronic device up and running for decades straight means you need to look carefully at each component and try to steer clear of any potential pitfalls.

The biggest one was the battery. More specifically, the fact he couldn’t use one. The lifetime of most rechargeable batteries is measured in hundreds of cycles, which for a device which will be charged by solar every day, means the battery is going to start showing its age in only 4 to 5 years. That simply wasn’t going to cut it.

[ANTALIFE] did some digging and realized that the solution was to use a supercapacitor, specifically the AVX SCMS22C255PRBA0. This is little wonder is rated for a staggering half million cycles, which in theory means that even with daily use it should still take a charge in the year 3300. In practice of course there are a lot of variables which will reduce that lifetime such as temperature fluctuations and the Earth being conquered by apes; but no matter what caveats you put on the figure it should still make 30 years without breaking a sweat.

Similar thought was given to choosing a solar cell with a suitably long lifetime, and he did plenty of testing and experimentation with his charging circuit, including some very nice graphs showing efficiency over time, to make sure it was up to snuff. Finally he walks the reader though his light-sensitive ring oscillator circuit which gives the device its pleasing “breathing” effect once the lights go down.

We’d love to bring you an update on this device in 30 years to see how close [ANTALIFE] got, but as we’re still trying to work the kinks out of the mobile version of the site we can’t make any guarantees about what the direct-brain interface version of HaD might look like. In the meantime though, you can read up on the long term battle between supercapacitors and traditional batteries.

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