Author: Bryan Cockfield

1827 Articles

You Don’t Need That Bulky CRT Oscilloscope Anymore

June 5, 2019 by 92 Comments

While it might be nice to use a $4,000 oscilloscope in a lab at a university or well-funded corporate environment, a good portion of us won’t have access to that kind of equipment in our own home shops. There are a few ways of getting a working oscilloscope without breaking the bank, though. One option is to find old CRT-based unit for maybe $50 on craigslist which might still have 60% of its original 1970s-era equipment still operational. A more reliable, and similarly-priced, way of getting an oscilloscope is to just convert a device you already have.

The EspoTek Labrador is an open-source way of converting a Raspberry Pi, Android device, or even a regular run-of-the-mill computer into a working oscilloscope. It’s a small USB device with about a two square inch PCB footprint that includes some other features as well like a signal generator and logic analyzer. It’s based on an ATxmega which is your standard Arduino-style AVR microcontroller but geared for low power usage. It looks as though it is pretty simple to use as well, and the only requirements are that you can install the software needed for the device on whatever computing platform you decide to use.

While the Labrador is available for sale at their website, it is definitely a bonus when companies offer products like this but also release the hardware and software as open source. That’s certainly a good way to get our attention, at least. You can build your own if you’d like, but if you’d rather save the time you have pre-built options. And it doesn’t hurt that most of the reviews of this product seem to be very favorable (although we haven’t tried one out ourselves). If you’d prefer an option without a company backing it, though, we have you covered there too.

New Circuits With Old Technology

June 2, 2019 by 15 Comments

Before the invention of transistors, vacuum tubes ruled the world. The only way to get amplification or switching (or any electrical control of current) back then was to use tubes. But some tube design limitations were obvious even then. For one, they produce an incredible amount of heat during normal operation, which leads to reliability issues. Tubes were difficult to miniaturize. Thankfully transistors solved all of these issues making vacuum tubes obsolete, but if you want to investigate the past a little bit there are still a few tubes on the market.

[kodera2t] was able to get his hands on a few of these, and they seem to be relatively new. This isn’t too surprising; there are some niche applications where tubes are still used. These have some improvements over their ancestors too, operating at only 30V compared to hundreds of volts for some older equipment. [kodera2t] takes us through a few circuits built with these tubes, from a simple subminiature vacuum tube radio to a more complex reflex radio.

Taking a walk through this history is an interesting exercise, and it’s worth seeing the ways that transistor-based circuits differ from tube-based circuits. If you’re interested enough to move on beyond simple radio circuits, though, you can also start building your own audio equipment with vacuum tubes.

Continue reading “New Circuits With Old Technology” →

Tiny Forklift Makes Unusable Space Usable

May 30, 2019 by 25 Comments

Houses with crawlspaces are fairly common in some geographic regions. The crawlspace can make it easier to access things like plumbing and electrical wiring, and can even be used as storage in homes that don’t (or can’t) have a basement. Along with improved building ventilation, these some of the perks compared to homes built on a solid slab of concrete. These crawlspaces aren’t exactly easy to get around in, though, but [Dave] has an easier way to get stuff in and out of these useful, but small, spaces.

Enter the crawl space forklift. Made with largely off-the-shelf components, the robot includes a few standard motors and linear actuators to move around and operate the front fork. That’s all pretty standard, but this build really shines with its use of FPV camera, monitor, and transmitter that allow the pilot to navigate the robot in the small space using remote control. For those safety-conscious among us, there is also a fire extinguisher ball on board which self-activates in case the robot catches on fire under his house.

This is a great, high-quality build that shows how common parts can make something revolutionary with the right idea. Identifying a problem and then building a solution, while not forgetting to spring for some safety equipment, can really make a difference even with something as simple as unoccupied space in a home. They can tackle tasks around the home, too.

Continue reading “Tiny Forklift Makes Unusable Space Usable” →

Robotic Cheetah Teaches A Motors Class

May 29, 2019 by 14 Comments

It seems like modern roboticists have decided to have a competition to see which group can develop the most terrifying robot ever invented. As of this writing the leading candidate seems to be the robot that can fuel itself by “eating” organic matter. We can only hope that the engineers involved will decide not to flesh that one out completely. Anyway, if we can get past the horrifying and/or uncanny valley-type situations we find ourselves in when looking at these robots, it turns out they have a lot to teach us about the theories behind a lot of complicated electric motors.

This research paper (gigantic PDF warning) focuses on the construction methods behind MIT’s cheetah robot. It has twelve degrees of freedom and uses a number of exceptionally low-cost modular actuators as motors to control its four legs. Compared to other robots of this type, this helps them jump a major hurdle of cost while still retaining an impressive amount of mobility and control. They were able to integrate a brushless motor, a smart ESC system with feedback, and a planetary gearbox all into the motor itself. That alone is worth the price of admission!

The details on how they did it are well-documented in the 102-page academic document and the source code is available on GitHub if you need a motor like this for any other sort of project, but if you’re here just for the cheetah doing backflips you can also keep up with the build progress at the project’s blog page. We also featured this build earlier in its history as well.

Creating A Sonic Landscape With Glitching CD Player

May 27, 2019 by 5 Comments

CDs were a great advancement in audio quality when they were first put on the market. There’s no vinyl-style degradation of the medium if it’s played over and over, and there’s no risk of turning them into a giant pile of ribbon while rewinding like a cassette tape. The one downside was that if you were to take them on the move you needed special hardware and software to prevent the inevitable skipping. If you look at the skipping not as a downside, though, but as a way to produce interesting music, you might end up with a pretty unique piece of hardware.

[Dmitry] is known for his interesting art installations, and the latest one uses parts from three 1988 Sony D2 CD players that have been reassembled in order to take advantage of a skipping and glitching CD. The modified equipment is able to play during pause or rewind thanks to a processor modification, and can also change the rotational speed of the disc. There are other pieces of hardware included for more fine control of glitching and skipping of the audio being read off of the CD.

The new device functions as a working musical instrument, although [Dmitry] says that it is more useful for deconstructing the information stored on the disc, and exploring the medium itself. Of course if you have enough motivation, you can find sounds from almost anywhere on (or in) the planet too.

Custom Electric Motorcycle Packs 6 KW

May 26, 2019 by 17 Comments

If you only need to travel at around 25 mph around town or to get a short distance to work, an electric bicycle might just be the best thing you can ride. It’s cheap, quick, and fun, and sometimes a great way to get some exercise too. If you want to dial up the amount of excitement, though, you’re going to want something with a little more power and speed. Something like an old dirt bike converted to a 6 kW electric motorcycle.

This is the latest build from [Boom Electric Cycles] and uses the frame from an early-90s Suzuki dirt bike as the foundation. From there it’s all new, though, as the engine was removed and replaced with 3 kW hub motors in each of the wheels. A 72-volt custom battery with 240 18650 cells pushed the amps through the motors, making this bike able to keep up anywhere except the fastest highways (if it’s street legal at all…).

Having about eight times more power than is found in a typical electric bicycle is sure to be a blast, but this build isn’t quite finished yet. Some of the trim panels need to be finished and the suspension needs to be adjusted, but it looks like it’ll be out and about any day now. Until then you’ll have to be satisfied with other projects that managed to cram in 3 kW per wheel.

Better Simulators With Homemade Potentiometers

May 24, 2019 by 22 Comments

Perhaps you’ve played a flight simulator before, using something like a mouse and keyboard. That’s a fine experience, but like any other activity you can get a lot more out of it if you put a little more effort into the experience. Some will upgrade to a joystick for a modest improvement, and others will build incredible accurate cockpit replicas down to the smallest detail. The builders of these “pits” are always looking for ways of improving their setups, and it’s from this world that we find a method of building specialized, inexpensive hall-effect sensors.

A hall-effect sensor is a circuit that outputs a voltage based on the presence of an external magnetic field. These can be used to make compasses, but with a permanent magnet in close proximity can also be used to create a potentiometer-like device at lower cost and with higher precision than a similarly-priced pot. There was a method of building these in the simulator world using the housing of a Bic pen and some strong glue, but [LocNar] has improved on this method as well. He repurposed some bearings and some stock metal tubing in order to fabricate a professional-level sensor at a fraction of the cost.

This build is essentially a solution for anyone needing a potentiometer that’s easier to build, less expensive, has higher precision, and interacts with a digital input in a much more predictable (and programmable) way. Certainly this has applications in the simulator world, but will work for many other applications. If you’ve never thought about the intricacies (and shortcomings) of potentiometers, some other folks have taken a deep dive into that as well.

Thanks to [Keith O] for the tip!