Building A Top-Notch Electret Microphone

November 2, 2020 by Lewin Day 25 Comments

Electret microphones are capable of high-quality output, and are prized for their smooth frequency response. However, unlike other types, they can’t simply be plugged directly into a mixing desk. Instead, they require special high-impedence circuitry to extract the audio signal for recording. [DJJules] is a big fan of these microphones, and decided to build a high-quality, easy to use circuit that he has shared with the community.

The goal of the project was to create a circuit to match the TSB2555B electret capsule that could be used with phantom power, and that could be built with easily obtainable parts. [DJJules] had used FETs in the past, but grew tired of routinely having to hunt for obsolete parts. Instead, this design relies on a dual OPA1642 op-amp, with its low quiescent current meaning it’s perfect for running off phantom power. This means the microphone needs no batteries, and using a dual op-amp enables the circuit to properly drive a balanced audio connection.

The circuit is designed to fit inside a common BM700 or BM800 microphone body, and the PCB can be ordered from PCBWay for those interested in building their own. There’s also a saddle on Shapeways that’s designed to neatly mount the electret capsule within the housing.

The final results are impressive, and this project would make a great entry into the DIY microphone space for anyone eager to start building their own gear. Of course, there are simpler builds if you’re looking for an easier way to get started. Video after the break.

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How Many Punches Does It Take?

November 2, 2020 by Chris Lott 3 Comments

Do you ever wonder just how many punches you have thrown? The answer is going to be different if you happen to use a punching bag as part of your exercise routine. So is the case with the [DuctTapeMechanic] and while restoring an old speed ball punching bag, he decided to combine his passions for sports and electronics by adding a punch counter.

Perhaps most interesting in this build is the method used to monitor the bag. A capacitance proximity sensor most often used for industrial automation is mounted in the wooden base. He just calls it “an NPN capacitive sensor” without mentioning part number but these are rather easy to find from the usual places. It has no problem sensing each punch — assuming you swing strong enough so that the bag comes near the sensor. Two battery packs, an Arduino, and an optocoupler round out the bill of materials. We were a little disappointed not to see any duct tape in the construction of this project, but since the electronics are outside and exposed to the elements, maybe duct tape will be used to install a roof in a future episode.

The [DuctTapeMechanic] likes to repurpose items which would otherwise be thrown away, which is something to be applauded. The frame of this punching bag was welded from a discarded metal bed frame (a regular occupant of crawl spaces and self storage places), and you might remember he repurposed the electric motor from a discarded clothes dryer last month, changing it into a disk sander.

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Self-Driving RC Truck Is A Master’s Thesis In Cybernetics And Robotics

October 31, 2020 by Lewin Day 7 Comments

RC cars are a fun pastime, but for many hackers, taking things to the next level involves making the cars drive themselves. For his Masters thesis, [Jon] did just that, building a self-driving robot truck that confidently cruises the floor of his laboratory.

The truck is based on a 1/14th scale Tamiya chassis, and had been fitted out by a prior group with an inductive charging system. On top of this platform, [Jon] added a Jetson TX2 to act as the brains of the system, hooking it up with a Slamtec RPLIDAR scanner to map its surrounding environment. There’s also a Teensy microcontroller onboard which handles synthesizing PWM signals for the radio control hardware that drives the truck, and a Logitech webcam up front for machine vision. The truck is capable of operating in a variety of modes, from full manual operation, to driving based on LIDAR mapping or with an AI controlling the truck based on camera data. The truck is programmed to drive a route including an inductive charging pad so it can keep its power levels up without human intervention.

It’s a great blueprint for a self-driving system, and [Jon]’s thesis goes into great detail on how everything works at the base level (available on this page as a 67 MB PDF). His Code is on Github for the curious. We’ve seen similar projects before too, like this robot that navigates its builder’s house using LIDAR. Video after the break.

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School Project Turns Plastic Waste Into Bricks

October 31, 2020 by Lewin Day 66 Comments

Many plastics are, in theory at least, highly recyclable. Unfortunately, in reality, most plastic ends up as waste instead, harming the environment and providing no ongoing value to society. Wanting to investigate possible ways to repurpose this material, [Rehaan33] built a rig to create bricks out of waste plastic for a school project.

The aim of the project is to take waste plastic, in this case high-impact polystyrene, and reform it into a brick that could be used as a low-cost building material. The material is shredded, before being packed into a steel mould and heated to 270 degrees in an oven. As polystyrene is a thermoplastic, it can readily be heated in this way for reforming without harming the material’s properties. Once heated, the mould is placed into the press rig, which uses parts of an old drill press to force down a steel plate, helping shape the final form of the brick.

While you’re unlikely to see old soda bottles used to build a skyscraper in New York any time soon, such techniques could be a good way to help eliminate plastic waste in impoverished areas and stem the flow of plastic into the world’s oceans. The project served as a useful learning experience, allowing [Rehaan33] to pick up skills in metalworking, machine design, and working with thermoplastics. Recycling plastics is a key area of interest for many, particularly in the 3D printing space, with many exploring ways to reuse thermoplastics in more efficient ways. If you’ve got your own project turning waste plastics into useful material, be sure to let us know!

Nerf Blaster Becomes Light Gun Controller

October 31, 2020 by Lewin Day 1 Comment

Traditional light guns rely on quirks of CRT technology, and thus don’t play well with modern LCD televisions and monitors. However, die hard retro gamers aren’t known for moving on from the classics, and have persevered to build new hardware to suit the games of old. In just this vein, [BrittLiv] grabbed some Nerf blasters, and built a pair of light guns that work with today’s hardware.

The build relies on Ultramarc’s light gun kits, which work in a similar way to the original Wiimote. A camera inside the blaster is used to triangulate an LED bar placed on top of the screen for clean and accurate tracking. [BrittLiv] combined the Ultramarc kit with some clever hacks to a Nerf DoubleStrike blaster, stealthily hiding the buttons inside to interface with the original trigger and cocking mechanism, as well as the locking tab in the rail.

There’s both a wired and wireless version, and the setup looks to be a great way to enjoy classics like Duck Hunt and Point Blank. The blasters work great with common platforms like MAME and RetroPi as the Ultramarc hardware emulates a standard USB mouse.

We’ve seen some wild light gun hacks before, like this build that uses cameras and maths to make things work without an LED bar at all! Video after the break.

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Color E-Ink Display Photo Frame Pranks [Mom]

October 30, 2020 by Dan Maloney 34 Comments

As a general rule, it’s not nice to prank your mother. Moms have a way of exacting subtle revenge, generally in the form of guilt. That’s not to say it might not be worth the effort, especially when the prank is actually wrapped in a nice gesture, like this ever-changing e-paper family photo frame.

The idea the [CNLohr] had was made possible by a new generation of multicolor e-paper displays by Waveshare. The display [Charles] chose was a generous 5.65″ unit with a total of seven colors. A little hacking revealed an eighth color was possible, adding a little more depth to the images. The pictures need a little pre-processing first, of course — dithering to accommodate the limited palette — but look surprisingly good on the display. They have a sort of stylized look, as if they were printed on a textured paper with muted inks.

The prank idea was simple — present [Mrs. Lohr] with a cherished family photo to display, only to find out that it had changed to another photo overnight. The gaslighting attempt required a bit more hacking, including some neat tricks to keep the power consumption very low. It was also a bit of a squeeze to get it into a frame that was slim enough not to arouse suspicion. The video below details some of the challenges involved in this build.

In the end, [Mom] wasn’t tricked, but she still seemed pleased with the final product. These displays seem like they could be a lot of fun — perhaps a version of the very-slow-motion player but for color movies would be doable.

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Circuit Sculpture Breathes Life Into Discrete Components

October 27, 2020 by Kristina Panos 5 Comments

We’ve probably all given a lot of thought to breathing this year in various contexts. Though breathing is something we all must do, this simple act has become quite the troublemaker in 2020. They say the best art imitates life, and [bornach]’s Astable Exhalation certainly does that, right down to the part about astability. It’s especially interesting that the end result — breathing, visualized — is so calming, it could almost be a meditative device.

There is nary a microcontroller to be found on this circuit sculpture, which uses a pair of astable multivibrator(s) to light two sets of LEDs that represent air being inhaled and exhaled. We like that [bornach] used two sized of exhale LEDs to represent droplets and aerosols in this beautiful circuit sculpture, and we love that most of the components were scavenged from old electronics and older projects.

Our Circuit Sculpture Challenge runs until November 10th, so even if you’re waiting to take the Remoticon workshop before entering, there’s still a little bit of time to whip something up afterward in the post-con adrenaline rush phase. If you need inspiration, check out some of the other contest entries or just surf through all things circuit sculpture.

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