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After looking at the many options for driving LED displays (5x7/8x8 matrix, 7/14/16/25 segment, common anode/cathode, single/bi-color/RGB), I put together this list of commonly used LED driver chips, to have a better picture of possible combinations, and use it as reference for future projects. The bottom 5 rows are not actually LED drivers, just substitutes (require current limiting resistors). Some of the driver chips (e.g. "8x8" in the "channels" column) provide internal multiplexing, being designed specifically for driving array of LEDs. The others, where "channels" is just one number, would require extra circuitry (e.g. transistors) and logic (micro controller code) for multiplexing. The "CA" column indicates "common anode", "CC" stands for common cathode. There seem to be more options for driving common anode LED displays, probably because sinking current (by the chips' LED outputs) allows for higher currents and als...

You are reading the first ever "review" of the Akafugu Nixie Modular Clock , a product yet to be released at the time of writing. Per, of Akafugu, generously offered to sell me the PCBs for this Nixie clock; the parts were sourced by myself. The Nixie Modular Clock shares a big chunk of the schematic with its older sibling, the Akafugu Nixie Clock . The goal of this latest design is, I assume from the name, the "modularity". Similar to the VFD Modular Clock , "shields" for various types and numbers of Nixie tubes will probably be developed soon. The hardware This Nixie Modular Clock is an Arduino-based, open source project, designed around ATmega328 running on internal oscillator at 8MHz. Like the Akafugu Nixie mk3, the high voltage source (180-200V) uses the MC34063 DC-DC converter, and the driver for Nixies is HV5812 . There are 3 buttons: 2 in the back, for setting up the time and alarm time, and another long-stem, protruding through the top board, for...

I recently bought on ebay the PCB for  this open source VFD shield , designed and made by Axiris, a company in Belgium. I was attracted by the solid documentation provided on their site, which includes the schematics (even Eagle files), assembly instructions, demo software, files for laser-cutting the enclosure. I should also mention the professional photos, rivaling those of the top sites (e.g. adafruit, sparkfun). Assembly went smoothly, as expected. I also expected it to work on the first try, like the other two VFD devices I built previously, the Ice Tube Clock and the akafugu VFD clock . I guess I ran out of luck :) But, as my kid would say, "losing is learning". This became an opportunity for me to actually go one step further than just soldering the components mindlessly (because the instructions are too easy :) This is how I learned what fascinating little devices VFDs are. They function similar to cathode ray tubes (CRT), used in the previous generation of TVs: ...

Once again, Sure Electronics modified their 32x16 3mm LED display, and this time not only cosmetically. The two 16-pin shrouded male connectors have been replaced with 10-pin connectors. And the worst thing is that the display now requires 12V for power! Maybe these new displays are intended for use in vehicles powered by 12V batteries. Or maybe designers thought a 12V power source is easier to access than a 5V one. In any case, the display has an on-board DC-DC switching regulator (with XL4013 ) to make the required 5V. For someone who needs to replace the older model with the new one, the immediate consequences are: the connector between the driver board (e.g. Wise Clock 4 ) and the display won't work; connections must be re-wired, probably using an adapter cable; either supply 12V to the board through the connector, or hack the display by soldering the 5V wire directly to the board (see the photos); the holes won't align anymore. The good news is that the display is electric...

As I pointed out in my review on Safecast bGeigie Nano kit, the size of the current software already reached the limit of processor's program memory of 30KB or so. From this point on, it is difficult (if not impossible) to add new code features, and that may require drastic code optimization or even disabling existing features. I thought that the easiest solution to keep this project up-to-date is by upgrading the processor, by entirely replacing the Fio board with an ATmega 644P plus a few extra components (e.g. LiPo charger). This makes the kit a bit more challenging to build, since it requires soldering SMD components, but could also save a few bucks. The device is still Arduino-compatible and programmable, like to Fio, using the FTDI breakout . Updated Jul 11, 2014 : As Rob suggested, I added the XBee module as well. New Eagle files are here . This is how the bGeigie Nano Plus PCB looks now. (I also added an option for the Fastrax UP501 module, a bit cheaper then the Ultim...

I finally finished assembling, after more than a year, my bGeigie Nano . At over $400, this was by far the most expensive Arduino project I have built to date. The feature-rich open-source Geiger counter is offered as a kit by Medcom for the price of $450 (of which, $75 is donated to Safecast organization ). I stubbornly insisted on sourcing the parts on my own, to save a few bucks and to get a closer look at the process. Let me tell you: this may be the only kit out there where the components bought individually are as expensive as the kit itself! Obviously, this kit was not designed to make a profit. Here is a price breakdown (for non-believers): - PCB (OSHPark) - $17 (3 for $52) - Pelican 1010 box (store) - $13 - Arduino Fio  - $25 - GPS module - $40 - OpenLog - $25 - OLED display - $25 - laser-cut plates - $25 - sensor LND7317 - $150 - iRover HV supply - $35 - LiPo battery - $10 - SD card - $10 - other electronic components - $5 - hardware (standoffs, screws etc) - $5 - shi...

Many months ago I bought, attracted by the clearance price, the PCB for the " Nixie Driver Board Rev A " from "Cogwheel circuit works" store. I was hoping that, with all documentation in place, I would be able to build it on my own, considering it's controlled by an ATmega328 and the software was available, though not the source code. First thing to note is that the board uses mostly SMDs. If anything went wrong (and there was a high chance, since the PCB was already described as a " mistake the board house made "), the board would become a coaster. The schematic includes some exotic components, like the HV513 Nixie driver , not offered by digikey. Others are the DS1302 RTC and the optional DS32KHZ oscillator for RTC, which I heard of for the first time. But thanks to the detailed BOM, gathering the components was relatively (some of them are already discontinued, for example) easy. High voltage for the Nixie tubes is generated by a hardware PWM und...

For "unknown" reasons, these days things don't move as fast as they used to. I have a dozen or so unfinished projects on my desk, most of them waiting for parts to arrive. And usually and unfortunately, when I get the long awaited part, something else is missing... or not fitting,... or not working. Today I was finally able to finish the " Open Source Nixie Tube Shield ", for which I pledged $15 on kickstarter in return for the PCB. Without paying attention to the schematic (was it even published before the campaign ended?), I thought it was just another variation of the same Nixie theme, which it really was. I expected to have all parts on hand already, including the Nixie K155ID1 driver Russian IC. Surprise! Instead, the circuit uses CD4028 decoder plus HV transistors. And that's where the 4 week wait is coming from. I liked the compactness of the board even before I soldered the almost 100 components. But I was a bit disappointed when I realized the shi...

This was not an easy project to finish. Anything that could go wrong, it did, due to a rare combination of ambiguous hardware kit design (that's what started it all), and bad luck (software bugs in Arduino IDE 1.0 nevertheless). In the end, I learned a few things, which made me a better person :) :) :) Please don't take this as a rant, nor as a (negative) review. As usual, the main purpose of the post is to document the experience and eventually help others troubleshoot similar problems they may have with the Arduinix shield kit . The first issue I had was not getting the high voltage (180V) required by the Nixie tubes. For some reason, the provided schematic and assembly instructions are ambiguous on the exact value of the C3. This made me look at other HV power supplies, with the conclusions captured in this post . Anyone taking a closer look at the Arduinix HV schematic will notice at least 3 differences compared to others using the same 555-based design: - the very importan...

I just finished assembling the latest version of akafugu VFD clock , the " MK2 ". Per, from akafugu, generously sent me the board for testing/review. It comes will all SMD components pre-soldered, and the processor pre-programmed. The rest of the components, all through-hole, I sourced on my own. Here is a photo of the kit as I put it together (I forgot to include the through-hole resistors though). Assembling was straightforward thanks to the combination of good board design and easy-to-follow instructions. The result is shown in the photo below. MK2 has some improvements over version 1: - newer processor ( Atmega32U4 , as the one used in Leonardo ); - 5V power source (vs 9V previously); - direct sketch upload from Arduino IDE ( no hacking required ); - integrated support (on-board 24LC256 eeprom) for four-letter-word feature; - all SMD parts (quite a few actually) come pre-soldered; - directly compatible with the existing (version 1) VFD display shields; - better clearance ...

There aren't many VFD clock kits out there that are software-compatible with Arduino (and by that I mean the "Arduino sketch" being compilable in Arduino IDE and uploadable through USB-FTDI). Most of these kits come with the microcontroller pre-programmed, so they can be built quickly and easily, with minimal effort (totally understandable instant gratification; nobody wants to end up with an expensive dud). Upgrading the software usually requires familiarity with the microcontroller toolchain (compile-build-flash), plus an ISP programmer. (Note: The only processor I am familiar with is AVR/Atmega.) I was going to build myself an Arduino-based VFD clock , one that can take a sketch through the FTDI cable. Instead of starting from scratch (choosing a schematic, making the board etc), I decided to try one of the only 2 open-source VFD clock kits I found that are based on Atmega processor and : Adafruit's Ice Clock Akafugu VFD modular clock I settled for the VFD modula...

I like Nixie tubes, especially when they are used in clocks, like this one I built a while ago. Although almost all Nixie clocks look the same, sometimes there is one that catches the eye. Such as the case of Agafuku Nixie Clock ,  designed in (and shipped from) Japan. The first thing to notice is that the final clock built from this kit is complete with enclosure, a rare find in the world of Nixie clock kits. Then, there is the look: simple, yet elegant, compact, yet functional. Obviously, I wanted one. Per, from Akafugu Corporation, graciously accepted to barter their Nixie clock kit for my Wise Clock 4 kit . Following is my brief review. The Akafugu Nixie clock kit looks professional starting with the box. Here are a few photos to prove that, taken as I was opening the package. I was surprised to find a power adapter included! The clock's electronics are distributed onto three PCBs, shown in the photo below: the power board (on the left), containing the 5V regulator and ...

The great team of Wyolum announced that their Raspberry Pi AlaMode is available for pre-order . This board, shown in the photo below, is Wyolum's answer to interfacing any number of hardware shields, sensors and servos to the Raspberry Pi . AlaMode is an Arduino compatible board that plugs right on top of the Raspberry Pi computer. It also gives you: extremely accurate real time clock DS3231 with backup battery micro SD slot direct headers for plugging in servos safe voltage translation between the Raspberry Pi and Arduino.

I am very "productive" lately (or maybe just wasteful with my time): this is my sixth post in as many consecutive days. I recently "discovered", in a design shop, this great looking travel clock made by Lexon . Things I like about it: beautiful shape/form/dimensions (low profile, small, light) and nice finish (brushed aluminum); apparent simplicity, with just one large(ish) button on the top and the lesser-used buttons placed on the bottom; LCD screen covering the whole face, showing more than the time (date, day, temperature, alarm); low consumption; powered by 2 CR2032 batteries, one for the clock, the other for the LCD backlight; attention to detail is everywhere, including the bottom rubber bumpers: the front ones are higher than the back ones, as seen in the next photo. This Lexon clock should be good inspiration for clock makers and clock designers. I hope one day my Wise Clock N will be as great as this is :)

This  is my original post on LunaTik . Coincidentally (I guess the Apple iPod Nano team thinks that they found the ideal shape and size), the latest, 7th, generation of iPod Nano has the exact same dimensions as the one it replaces (and for which LunaTik was designed). So, LunaTik and TikTok get a new (and well deserved) lease on life, from Apple itself. More, LunaTik is actually mentioned in one of Apple's presentations , officially endorsing the brand. Actually, even the current (6th) generation iPod Nano can be software-upgraded through iTunes with 16 new clock faces (some of them shown in the photo below, courtesy of LunaTik team, sent by email via kickstarter). But this is not all. As I anticipated, watch "modules"  (shown below) are being developed to be hosted by LunaTik. This could become the flagship of the designer watches. Can you imagine high-end watchmakers producing watches that fit LunaTik? How far fetched is to see a custom made-for-LunaTik Omega, for exam...

A while ago I received the good-looking  I2SD kit  from Wyolum . This is another open source project created and generously shared by the same team that brought us ClockTHREE and C3Jr . The I2SD kit is pictured below. As you can see, it is mostly SMD (0805 and SOIC packages). Not for a novice, but definitely easy to solder by anyone with a steady hand and a good pair of eyes. As always, when I assemble a kit, I try to skip the "read the manual" part. I don't recommend this to anyone though. This is just a test for me to assess how user-friendly the kit is. (Note: Ironically, this test would fail for my own  Wise Clock 3 kit because of the 3 resistors of 4K7. One really need to know exactly where those resistors go (R5, R6 and R7). An improvement in a future version of Wise Clock 3 would be to have the resistor values on the silkscreen, as C3Jr has.) Well, the I2SD kit passed the "no manual required" test, which means that the kit is well thought and desi...