This Bike Sonar is Off the Chain

On paper, bicycling is an excellent form of transportation. Not only are there some obvious health benefits, the impact on the environment is much less than anything not directly powered by a human. But let’s face it: riding a bike can be quite scary in practice, especially along the same roads as cars and trucks. It’s hard to analyze the possible threats looming behind you without a pair of eyes in the back of your head.

radar-sweep-display[Claire Chen] and [Mark Zhao] have come up with the next best thing—bike sonar. It’s a two-part system that takes information from an ultrasonic rangefinder and uses it to create sound-localized pings in a rider’s ears. The rangefinder is attached to a servo mounted on the seat post. It sweeps back and forth to detect objects within 4 meters, and this information is displayed radar-sweep-style graphic on a TFT screen via a PIC32.

Though the graphic display looks awesome, it’s slow feedback and a bit dangerous to have to look down all the time — the audio feedback is by far the most useful. The bike-side circuits sends angle and distance data over 2.4GHz to another PIC mounted on a helmet. This PIC uses sound localization to create a ping noise that matches the distance and location of whatever is on your tail. The ping volume is relative to the distance of the object, and you just plug headphones into the audio jack to hear them. Bunny-hop your way past the break to check it out.

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Semi-automatic Mouse Requires No Permit

When [Kerry]’s son asked him if there was a way to make a mouse click rapidly, he knew he could take the easy way and just do it in software. But what’s the fun in that? In a sense, it’s just as easy to do it with hardware—all you have to do is find a way to change the voltage in order to simulate mouse clicks.

[Kerry] decided to use the venerable 555 timer as an astable oscillator. He wired a momentary button in parallel with the left mouse button. A 50k mini pot used as the discharge resistor allows him to dial in the sensitivity. [Kerry] found that he maxed out around 5 clicks per second when clicking the regular button, and ~20 clicks per second with the momentary button as measured here. The mouse still works normally, and now [Kerry]’s son can totally pwn n00bs without getting a repetitive stress injury. M1 your way past the break to check out [Kerry]’s build video.

There are lots of other cool things you can do with an optical mouse, like visual odometry for cars and robots.

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“What is My Purpose?” You Amplify and Display Signals.

[Andy_Fuentes22] likes to stream music, but is (understandably) underwhelmed by the sound that comes out of his phone. He wanted to build something that not only looks good, but sounds good. Something that could stream music through a Chromecast or a Raspi, but also take auxiliary input. Something awesome, like the Junkbots Sound System.

The ‘bots, named LR-E (Larry) and R8-CHL (Rachel), aren’t just cool pieces of art. They’re both dead-bug-walking bots with an LM386-based amplifier circuit and an AN6884-based VU meter in their transparent, industrial relay bodies. LR-E is the left channel, and his lovely wife is the right channel. The best part is that they are wired into the circuit through their 3.5mm plug legs and the corresponding jacks mounted in the Altoids tin base.

[Andy] built this labor of love from the ground up. He started with some very nice design sketches and took a bazillion pictures along the way. We think it sounds pretty good, but you can judge for yourself after the break. If VU meters are your jam, here’s another that’s built into the speaker.

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All I Want for Christmas is a 4-Factor Biometric Lock Box

It’s the most wonderful time of the year! No, we’re not talking about the holiday season, although that certainly has its merits. What we mean is that it’s time for the final projects from [Bruce Land]’s ECE4760 class. With the giving spirit and their mothers in mind, [Adarsh], [Timon], and [Cameron] made a programmable lock box with four-factor authentication. That’s three factors more secure than your average Las Vegas hotel room safe, and with a display to boot.

Getting into this box starts with a four-digit code on a number pad. If it’s incorrect, the display will say so. Put in the right code and the system will wait four seconds for the next step, which involves three potentiometers. These are tuned to the correct value with a leeway of +/- 30. After another four-second wait, it’s on to the piezo-based knock detector, which listens for the right pattern. Finally, a fingerprint scanner makes sure that anyone who wants into this box had better plan ahead.

This project is based on Microchip’s PIC32-based Microstick II, which [Professor Land] starting teaching in 2015. It also uses an Arduino Uno to handle the fingerprint scanner. The team has marketability in mind for this project, and in the video after the break, they walk through the factory settings and user customization.

We have seen many ways to secure a lock box. How about a laser-cut combination safe or a box with a matching NFC ring?

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Modular Tap-Dancing Robot Can Shuffle Ball Change

Electromechanical solenoids are pretty cool devices. Move some current through an electromagnet and you can push a load around or pull it. If you’re MIT student [Lining Yao], you can use them to dance. [Lining] built TapBot, a re-configurable set of tap-dancing robots that are both modular and modern. She even rolled her own solenoids.

The one with the eye stalk is the bridge, and it’s connected to a computer over FTDI. The other nodes attach to the bridge and each other with small magnets that are designed to flip around freely to make the connections. These links are just physical, though. The nodes must also be connected with ribbon cables.

Each of the nodes is controlled by an ATtiny45 and has a MOSFET to drive the solenoid at 8-12 V. [Lining] snapped a small coin magnet to the end of each solenoid slug to provide a bigger surface area that acts like a tap shoe. TapBot can be programmed with one of several pre-built tap patterns, and these can be combined to make new sequences. The curtain goes up after the break.

There are other ways to make things dance, like muscle wire. Check out this whiteboard pen that uses nitinol to dance to Duke Nukem.

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LEGO Strain Wave Gear is Easy on the Eyes

We are continually amazed by the things people do with LEGO and Technics, especially those that require incredible engineering skill. There’s an entire community based around building Great Ball Contraptions, which are LEGO Rube Goldberg machines that move tiny basketballs and soccer balls from one place to another. Except for a few rules about the input and output, the GBC horizons are boundless.

Famed GBC creator [Akiyuki] recently built a GBC module that’s designed to show the movement of strain wave gear systems. These types of gear systems are used in industrial applications where precision is vital. Strain wave gears are capable of reducing gear ratios in a small footprint.

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Arduino Laser Pinball is On Target

Have you ever wanted to roll your own pinball machine? It’s one of those kinds of builds where it’s easy to go off the deep end. But if you’re just getting your feet wet and want to mess around with different playfield configurations, start with something like [joesinstructables]’ Arduino Laser Pinball.

It’s made from meccano pieces attached with standoffs, so the targets are easy to rearrange on the playfield. [joesinstructables] wanted to use rollover switches in the targets, but found that ping pong balls are much too light to actuate them. Instead, each of the targets uses a tripwire made from a laser pointing at a photocell. When the ping pong ball enters the target, it breaks the beam. This triggers a solenoid to eject the ball and put it back into play. It also triggers an off-field solenoid to ring a standard front-desk-type bell one to three times depending on the target’s difficulty setting.

The flippers use solenoids to pull the outside ends of levers made from meccano, which causes the inside ends to push the ball up and away from the drain. Once in a while a flipper will get stuck, which you can see in the demo video after the break. An earlier version featured an LCD screen to show the score, but [joesinstructables] can’t get it to work for this version. Can you help? And do you think a bouncy ball would actuate a rollover switch?

This isn’t the first pinball machine we’ve covered. It’s not even the first one we’ve covered that’s made out of meccano. Here’s an entire Hacklet devoted to ’em. And remember when an Arduino made an old table great again?

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