Retro Modern Nixie Clock

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[Reboots] is a humble hacker who enjoys nixie tubes. So when he saw an old General Electric battery charger for sale at a hamfest, he thought: “that case would make a nice clock…”

He was first exposed to nixie tube clocks a few years ago when his brother gave him a DIY nixie clock kit from [Peter Jensen's] website TubeClock.com — it was an easy build, and worked very well. It also introduced him to a unique driver for nixie tubes, an HV5622 high-voltage shift register made by Supertex inc. Compared to the traditional (and rare) 74141 nixie driver chips or discrete transistor drivers, the HV5622 is much smaller, requires less microcontroller I/O’s, and is not as picky when it comes to powering it.

The nixie tubes he chose for the project came from a lot sale on eBay, Russian surplus IN-12 tubes. He even managed to find an english datasheet for them!

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Re-engineering some FM transmitter firmware

[Furrteck] had a little adventure with this FM transmitter he picked up on eBay. It worked alright, but he wanted to be able to scan through the frequencies, and to have the device return to the same settings after power cycling. He cracked it open and got to work to achieve all of his goals.

The device is driven by an ATmega48, and there’s a 6-pin ISP header on the board. An initial read of the chip wouldn’t work, and he soon discovered the unstable power supply was to blame. After connecting his own regulated source he could read the chip id without a hitch, but the code is locked so no dumping was possible. Fortunately he managed to trace out the board, and includes a full schematic in his write up. With this in hand he erased the chip and started programming his own firmware from the ground up.

The video after the break shows off the completed project. He can now scan through frequencies with audio feedback to let he know when he’s found a station to hijack. The new code will also write a tuned station to EEPROM for use the next time the rig is powered up.

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Multi-channel analog input module is a good jumping-off point for many projects

[Scott Harden] has already produced some projects which measure analog inputs. But he’s got plans for more and wanted a base system for graphing analog signals. You can see the small board next to his laptop which offers the ability to sample up to six signals and push them to a PC via USB.

The ATmega48 and a few supporting components are all you’ll find on that board. The USB connection is taken care of by an FTDI cable. He went that route because the cables are relatively cheap, easy to come by, and already have driver support on all the major operating systems. If you look at the screen you can see a window graphing one analog input in real-time. He wrote this in Python (which is once again a cross-platform tool) and it has no problem graphing all six inputs at once.

This is immediately useful as an upgrade to [Scott's] ECG machine. His future plans include a Pulse Oximeter, EEG, and EEG.

LED case lights reflect CPU usage

A lot of Linux users include system monitor information in their status panel so that they can see when the CPU is grinding away. [Kevin] is taking the concept one step further by changing his case lights based on CPU usage. Above you can see green, orange, and magenta, but [Kevin's] implementation uses the full spectrum of color.

The project is based on an ATmega48. It’s running the V-USB stack and connects to one of the motherboard’s internal USB ports. This lets him easily push the CPU usage data over to the microcontroller where it is translated into color. One RGB LED has been installed behind each fan panel on the front of the case, with a white LED above and below as an accent. Pulse-width modulation via some MOSFETs lets him mix and match for just the right color. He’s powering the add-on off of the PSU rails rather than USB so that it turns off when the computer goes to standby.

Don’t miss [Kevin's] explanation of the system, and a demo of it in action after the break.

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Build a binary wall clock for just a few bucks

The weekend is almost here and if you’re looking for an afternoon project consider building your own binary wall clock. [Emihackr97] built the one you see above using parts on hand, but even if you put in an order for everything, it won’t cost you much.

He used a cardboard box as the housing for the clock, marking a grid for the LEDs on the face and drilling holes to house them. Two columns for hours and another two for minutes let the clock display 24-hour time with alternate firmware for 12 hour time. Since there are two buttons – one to set hours, the other to set minutes – a little coding would make it possible to select between the two either by clicking both buttons at once, or holding down one button.

[Emihackr97] is driving the display with an ATmega48, which is a pin-compatible replacement for the ATmega168/328. Those chips are the type most commonly found on Arduino boards an indeed this project is running the Arduino bootloader, but uses an ISP programmer and breadboarded circuit to keep the costs low. There are plenty of pins to drive the 13 LEDs directly, making the soldering quick and painless. Check out a demo clip after the break.

If you’re successful at this build and get the itch for something with more style, there’s a ton of ways to spice up the look of a binary clock.

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[Scott] made a single-chip Hellschreiber on earth

[Scott Harden] is drilling teeth by day and designing radios that send secret messages by night. He’s set his sights on the Hellschreiber protocol which was used by the Germans in World War II along with their Enigma encryption system. The protocol is a viable alternative for transmitting and receiving code in environments with too much background noise for other communication systems.

His goal was to develop his own transmitter using just one microcontroller. He picked an ATmega48 and coupled it with a 40 MHz crystal oscillator. [Scott] mentions that there is no other hardware necessary, but static messages stored in an array so you’d need some other hardware to push your own characters through via the chip’s UART or otherwise. The AVR sends messages by converting the data into audio using PWM. That signal is fed into the crystal oscillator, which produces an amplitude modulated signal (AM) that can then be transmitted.

Check out his video after the break for a demonstration. He’s decoding the transmitted data using a free program called Ham Radio Deluxe.

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Small POV device shows off some big features

We’ve already added the components needed to build [Rucalgary's] tiny POV device to our next parts order. The little device sets a new standard for tiny persistence of vision boards. Instead of relying on the user to find the best speed and timing for swinging the board around, [Rucalgary] used an accelerometer. This is the point at which we’d usually groan because of the cost of accelerometers. We’re still groaning but this time it’s for a different reason.

The accelerometer used here is a Freescale MMA7660. It’s an i2c device at a super low cost of less than $1.50. The reason we’re still groaning is that it comes in a DFN-10 package that is a bit harder to solder than SOIC, but if you’ve got patience and a good iron it can be done. An ATmega48 drives the device, with 8 LEDs and one button for input. On the back of the board there’s a holder for a CR2032 coin cell battery and a female SIL pin header for programming the device.

Check out the video demonstration embedded after the break. We love it that the message spells and aligns correct no matter which way the little board is waved.

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