BPSK31 is an extremely popular mode for amateur radio operators; it’s efficient and has a narrow bandwidth and can be implemented with a computer sound card or an Arduino. Just like it says on the tin, it’s phase shift keying, and a proper implementation uses a phase detection circuit or something similar. [Craig] thought it would be fun to build an analog BPSK31 demodulator and hit upon the idea of doing this with amplitude demodulation. No, this isn’t the way you’re supposed to do it, but it works.
Data is transmitted via BPSK31 with a phase shift of 180 degrees being a binary 0, and no phase shift being a binary 1. [Craig]’s circuit uses an op-amp and a pair of diodes to do a full wave rectification of the signal, which basically makes a binary 1 logic high, and binary 0 logic low.
This rectified signal is then fed into a comparator, making the output go high when the signal is above 2V, and low when the signal is below 1V. That’s all you need to do to get bits out of the signal, all [Craig] had to do after that was figure out a way to sample it.
A 555 set up in astable mode running at 31.25 Hz provides the clock, synchronized with the signal by connecting the comparator’s output to the 555 trigger input. The timer clock ends up being slightly slower, but thanks to the varicode character set, the maximum number of binary ones the circuit will see is nine; every time the trigger sees a zero, the timer’s trigger is reset, re-synchronizing the receiver’s clock.
Yes, it’s a hack, and no, this isn’t how you’re supposed to receive PSK. It does, however, work, and you can thank [Craig] for that.
This full-size replica blaster from Star Wars, most iconically used by Han Solo and Princess Leia, has everything. Flashing LEDs, blaster noises, LEGO, and yes, even an Arduino. Not bad for [Baron von Brunk]’s first project to use an Arduino!
The blaster was based on electronics and LEGO that were lying around and was intended for use for Star Wars Day 2014. (May the Fourth be with you.) “Lying around” in this sense might be a bit of an understatement for [Baron von Brunk], as the design of the blaster required the use of the LEGO Digital Designer and 400 blocks, some of which are quite rare.
The electronics for the project are tied to a moving trigger mechanism (also made from LEGO). The trigger mechanism hits a momentary pushbutton which tells the Arduino to activate the LEDs and a separate 555 timer and sound recording/playback device which handles the classic blaster sounds. The whole thing is powered by a 9V battery and housed in the front of the blaster, and all of the code (and the LEGO schematics) are available on the project’s site.
This is quite an impressive replica, and the craftsmanship that went into the build shows, especially in the LEGO parts. We think Han Solo would indeed be proud! If you’re ready to go even further with Star Wars and LEGO, you might want to check out this barrel organ that plays the Star Wars theme.
Morse code was once a staple of the communications industry, but with advancing technology it has become relegated almost exclusively to movies and a niche group of ham radio operators. [Jan] has created a device which might not put a stop to this trend, but will at least educate children on the basics of how Morse code works by visually displaying Morse code as it’s generated.
The setup is fairly simple. An old momentary switch (which could easily be used in an actual Morse code setup) activates two pieces of circuitry. The first is a 555 timer circuit that creates an audible tone when the switch is pressed so the user can hear exactly what an operator would hear when decoding a real Morse code message.
The second piece of circuitry is where the real genius lies: a continuously spinning roll of glow-in-the-dark tape is placed in front of a white LED. When the switch is pressed, the LED turns on, which produces dots and dashes on the roll of tape as it passes by. This eliminates the need for rolls of paper or a more complicated moving pen/pencil setup to draw on the paper which might also be less child-proof.
While [Jan] built this as a toy, the children who used it thoroughly enjoyed it! They even decoded some Morse code messages and used the device to practice on it. After a while they’ll easily be able to master the Morse code trainer!
[Nick] wrote in to tell us about his first blog post. He’s showing off a PWM LED driver he build around a 555 timer. This project uses a lot of basics; some 555 experience, PCB etching, and surface mount soldering. We’d like to know more about the blue substrate on his circuit board!
After seeing the BOM spreadsheet with KiCAD integration a couple of weeks back, [Vassilis] sent in a link to his own Excel-based Bill of Materials helper. We’re wondering if anyone has a similar tool that will work with Open Office?
While we’re on the topic of downloadable documents, here’s a reference PDF for all types of DC measurements. The collection is a free offering from Keithley. [Thanks Buddy]
Since you’re brushing up on your knowledge you may also be interested in a free online microcontroller course offered by UT Austin. They’re targeting the Tiva C Launchpad as the dev board for the class.
This website seems to be a little creepy, but the teardrop shaped 3D printed music box which is being shown off is actually rather neat.
Hackaday Alum [Phil Burgess] threw together a point and shoot camera for Adafruit. It’s a Raspberry Pi, camera board, touchscreen display, and USB battery all rubber banded together. The processing power of the RPi is used to add image processing effects which are shown off in the demo video.
We don’t own a DeLorean. If we did, we’d probably follow the lead of Queen’s University Belfast and turn it into and electric vehicle. [Thanks Jake]
The 3D photocopiers are coming. Here’s a hacked together proof-of-concept from [Marcelo Ruiz]. After laser scanning the part is milled from floral foam.
For the Ottawa Mini-Maker Faire this year, [Steven Dufresne] created an electronic take on the classic mechanical music box.
A typical music box uses a sequence of bumps on a rotating drum to pluck the tuned teeth (called lamellae) of a metal comb. Steven ditched the drum and comb and replaced them with a strip of paper and a single 555 timer. The timer is configured as an astable oscillator with a fixed capacitor and charging resistor. The discharge resistor is selected via a series of 13 shaped wires that drag along the strip of paper. When a wire drags over a hole, it is connected to a copper pad below that is soldered to a specific resistor. This completes the circuit and generates a tone specific to the resistor selected.
While the electrical aspects of the project are fairly simple (not even requiring a circuit board), the mechanical parts are much more sophisticated. Steven had problems getting the dragging wires to make good contact and keeping the paper roll pulled tight. He outlines all of these challenges and how he solved them in his very thorough video summary (embedded after the break). With all of his incremental improvements to the design, the finished music box stood up to a whole 14 hours of abuse at the Faire.
Continue reading “Completely analog electronic music box”
From simple buzzers to an Atari Punk Console, the simple 555 timer chip is the foundation of a whole lot of interesting lo-fi synth projects perfect for beginners. [Steven] put together a great tutorial for using the 555 timer in a rudimentary synth, and even went so far as to build a simple electronic player piano able to play a song from a sheet of paper with punched holes.
The basic 555 oscillator circuit is very simple – just a few caps and resistors and powered by a few batteries. [Steven] built the simplest 555 circuit, but used a line of graphite drawn on a piece of paper for the resistor controlling the frequency. It’s basically a drawdio built on a breadboard, and easy enough to build for even the most neophyte electronic tinkerer.
Going one step further, [Stephen] drew a long thick line of pencil graphite on a piece of paper and mounted eleven wire loops attached to the circuit over his improvised resistor. After cutting a few holes in a piece of paper, he was able to create a simple player piano with his 555 synth. It worked well enough to play Greensleeves, and is the perfect project for the budding electronics hacker.
Continue reading “A 555 player piano”
[Kenneth Finnegan] took the focus of a great design and redirected it to solve his own problem. What results is this lead acid battery charger based on the 555 timer. It’s not a top-of-the-line, all the bells and whistles type of charger. But it gets the job done with a readily available IC and no need to code for a microcontroller.
The original idea came from a solar battery charger entered in the 555 timer contest. The main difference in application between that and [Kenneth’s] application is the source. A solar array or wind turbine is limited on how much juice it can produce. But mains power can push a shocking (har-har) amount of current if you’re not paying attention. Herein lies the alterations to the circuit design. To control this he’s using a Laptop power supply as an intermediary and only implementing the constant current portion of the tradition 3-stage lead acid charging profile (those stages are explained in his write up).
He did a talk on the charger at his local radio club. You can see the 90-minute video after the break.
Continue reading “555-timer charges lead acid batteries”