[Ben Krasnow] Builds a One-Component Interferometer

When we think of physics experiments, we tend to envision cavernous rooms filled with things like optical benches, huge coils in vacuum chambers, and rack after rack of amplifiers and data acquisition hardware. But it doesn’t have to be that way – you can actually perform laser interferometry with a single component and measure sub-micron displacements and more.

The astute viewer of [Ben Krasnow]’s video below will note that in order to use the one component, a laser diode, as an interferometer, he needed a whole bunch of support gear, like power supplies, a signal generator, and a really, really nice mixed-signal oscilloscope. But the principle of the experiment is the important bit, which uses a laser diode with a built-in monitoring photodiode. Brought out to a third lead, older laser diodes often used these photodiodes to control the light emitted by the laser junction. But they also respond to light reflected back into the laser diode, and thanks to constructive and destructive interference, can actually generate a signal that corresponds to very slight displacements of a reflector. [Ben] used it to measure the vibrations of a small speaker, the rotation of a motor shaft, and with a slight change in setup, to measure the range to a fixed target with sub-micron precision. It’s fascinating stuff, and the fact you can extract so much information from a single component is pretty cool.

We really like [Ben]’s style of presentation, and the interesting little nooks and crannies of physics that he finds a way to explore. He recently looked at how helium can kill a MEMS sensor, an equally fascinating topic.

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Pedal Far With A Solar Powered Tricycle

More and more electric bikes have been rolling out into the streets lately as people realize how inexpensive and easy they are to ride and use when compared to cars. They can also be pedaled like a normal bike, so it’s still possible to get some exercise with them too. Most have a range somewhere around 10-30 miles depending on battery size, weight, and aerodynamics, but with a few upgrades such as solar panels it’s possible to go much, much further on a charge.

[The Rambling Shepherd] had a tricycle (in the US, generally still considered a bicycle from a legal standpoint) that he had already converted to electric with a hub motor and battery, and was getting incredible range when using it to supplement his manual pedaling. He wanted to do better, though, and decided to add a few solar panels to his build. His first attempt didn’t fare so well as the 3D-printed mounts for the panel failed, but with a quick revision his second attempt survived a 50-mile trip. Even more impressive, he only had his battery half charged at the beginning of the journey but was still able to make it thanks to the added energy from the panels.

If you’re thinking that this looks familiar, we recently featured a tandem tricycle that was making a solar-powered trip from Europe to China with a similar design. It has the advantage of allowing the rider to pedal in the shade, and in a relatively comfortable riding position compared to a normal bike. Future planned upgrades include an MPPT charge controller to improve the efficiency of the panels.

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Radar in Space: The Gemini Rendezvous Radar

In families with three kids, the middle child always seems to get the short end of the stick. The first child gets all the attention for reaching every milestone first, and the third child will forever be the baby of the family, and the middle child gets lost in-between. Something similar happened with the U.S. manned space program in the 60s. The Mercury program got massive attention when America finally got their efforts safely off the ground, and Apollo naturally seized all the attention by making good on President Kennedy’s promise to land a man on the moon.

In between Mercury and Apollo was NASA’s middle child, Project Gemini. Underappreciated at the time and even still today, Gemini was the necessary link between learning to get into orbit and figuring out how to fly to the Moon. Gemini was the program that taught NASA how to work in space, and where vital questions would be answered before the big dance of Apollo.

Chief among these questions were tackling the problems surrounding rendezvous between spacecraft. There were those who thought that flying two spacecraft whizzing around the Earth at 18,000 miles per hour wouldn’t work, and Gemini sought to prove them wrong. To achieve this, Gemini needed something no other spacecraft before had been equipped with: a space radar.

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Car Revival According to Tesla

Frankencars are built from the parts of several cars to make one usable vehicle. [Jim Belosic] has crossed the (finish) line with his Teslonda. In the most basic sense, it is the body of a Honda Accord on top of the drive train of a Tesla Model S. The 1981 Honda was the make and model of his first car, but it wasn’t getting driven. Rather than sell it, he decided to give it a new life with electricity, just like Victor Frankenstein.

In accord with Frankenstein’s monster, this car has unbelievable strength. [Jim] estimates the horsepower increases by a factor of ten over the gas engine. The California-emissions original generates between forty and fifty horsepower while his best guess places the horsepower over five-hundred. At this point, the Honda body is just holding on for dear life. Once all the safety items, like seatbelts, are installed, the driver and passengers will be holding on for the same reason.

This kind of build excites us because it takes something old, and something modern, and marries the two to make something in a class of its own. And we hate to see usable parts sitting idle.

Without a body, this electric car scoots around with its driver all day, and this Honda doesn’t even need the driver inside.

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Garage Distance Sensor Kicks Tennis Ball To Curb

Those with small garages might be familiar with the method of hanging a tennis ball from a ceiling to make sure they don’t hit the back wall with their car. If the car isn’t in the garage, though, the tennis ball dangling from a string tends to get in the way. To alleviate this problem, [asaucet] created a distance sensor that can tell him when his car is the perfect distance from the garage wall.

At the heart of the distance sensor is an HC-SR04 ultrasonic rangefinder and a PIC16F88 microcontroller. [asaucet] uses a set of four LEDs to alert the driver how close they are to the garage wall. [asaucet] also goes into great detail about how to use an LCD with this microcontroller for setting up the project, and the amount of detail should be enough to get anyone started on a similar project.

While this isn’t a new idea, the details that [asaucet] goes into in setting up the microcontroller, using the distance sensor, and using an LCD are definitely worth looking into. Even without this exact application in mind, you’re sure to find some helpful information on the project page.

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Portable Stir-Fry Range

If you love a good stir-fry, you know that it can be a challenge to make on your stove at home. Engineer gourmet and Youtuber [Alex French Guy Cooking], in collaboration with [Make:], whipped up a portable range capable of making delectable stir-fry.

There are three major problems when it comes to cooking stir-fry: woks are typically unstable on normal burners, those burners don’t tend to heat from a center point out, and they usually aren’t hot enough. [Alex]’s 12,000BTU portable stove is great for regular applications, but doesn’t cut it when it comes to making an authentic stir-fry.

To focus the burner’s heat, he cut and bent a stainless steel baking ring into the shape of an exhaust nozzle — not unlike a jet engine — and lightly modified the range to accommodate the nozzle. He also added a larger baking ring with air flow holes for the wok to rest on. Two down, but there’s the issue of it not being hot enough.

So, why not use two butane canisters to double the output to 22,200 BTUs!

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Simple Range Testing for LoRa Modules

WiFi and Bluetooth have their use cases, but both have certain demands on things like battery life and authentication that make them unsuitable for a lot of low-power use cases. They’re also quite limited in range. There are other standards out there more suitable for low-power and wide area work, and thankfully, LoRa is one of them. Having created some LoRa pagers, [Moser] decided to head out and test their range.

Now, we’ve done range tests before. Often this involves sending one party out with a radio while the other hangs back at base. Cellphones serve as a communications link while the two parties go back and forth, endlessly asking “Is it working now? Hang on, I’ll take a few steps back — what about now?”

It’s a painful way to do a range test. [Moser]’s method is much simpler; set a cellphone to log GPS position, and have the pager attempt to send the same data back to the base station. Then, go out for a drive, and compare the two traces. This method doesn’t just report straight range, either — it can be used to find good and bad spots for radio reception. It’s great when you live in an area full of radio obstructions where simple distance isn’t the only thing affecting your link.

Build details on the pagers are available, and you can learn more about LoRa here. While you’re at it, check out the LoRa tag for more cool builds and hacks.