Chumby Nixie clock

With my limited (read "non-existent") crafting resources (e.g. space, tools), the easiest way to enclose my Arduinix clock was by recycling my late Chumby's shell. Things almost magically fit together, with minimal thinking and work. I was able to cram inside the box a hand-wired Wiseduino with an Arduinix-remix shield and a 4-tube board.

The old Wiseduino would have come in handy if I had any left. I made one using the protoshield from Sparkfun, which also has a connector for the Bluetooth JY-MCU module. Beside the ATmega328, this pseudo-Wiseduino board includes a DS1307 with coin backup battery and a 7805 voltage regulator.

The tube board is attached with screws to an empty board that plugs in the Arduinix-remixed shield. (Note that one reason for "remixing" Arduinix was to re-arrange the parts sticking out, namely the mosfet and the capacitors, so that it allows another shield to be stacked on top.)

The clock has no user button (I glued the original snooze button on top, would have required extra work to re-use it), so the time is set through the bluetooth interface, similarly to my other Arduino Nixie clock.

The sketch (compiled with Arduino 1.0.4) is available here. Note that, unlike the original Arduinix sample sketch, the nixie-driving code is now using interrupts. This decouples the display logic from the clock functionality, also allowing for the addition of a buzzer alarm.

Custom enclosure for Wise Clock 4

John, aka broHogan, the creator of DIYGeigerKit, skillfully built a nice enclosure for his Wise Clock 4, a potential inspiration to others. From his email:

The case is made from Cocobolo (rosewood) from a slab I bought in Costa Rica. The splines are ebony. In about a year it will turn a nice deep red.

It's really not this brown,

more like this.
Buttons also cocobolo. Holes drilled in the ends go over pushbuttons.

The router jig used to cut the slots for the splines.

And this reminds me of a joke. How do you double the value of a Jugo car? You fill up the tank. Got it? :)

Thanks John, I really appreciate it.

Wyolum 3rd annual Innovation Grant - 2013

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This is the place to submit your project, find out the rules and deadline, and generally learn more about this generous team of innovators!

Eulogy for my Chumby

My beloved Chumby One died today. I first thought to be a software glitch, since the booting seemed to take a long time, then it seemed to re-boot itself after a little while. After a few cold resets, the screen started to literally flash, like the flash of a camera, once every 2 or 3 seconds. Not a good sign. I opened it up, for the first time. Beautiful on the inside too. Regretfully, it does not look like something I could repair.

My Chumby served me faithfully and inspired me (I am not kidding) for the last 4 years or so, mainly as a desk clock . It had all the features I wanted in such a device: fairly sized touch screen, good WiFi, great speaker (bass reflex nonetheless), reasonable radio, rotary encoder for volume (or menu scrolling), backup battery, USB socket, internal SD card for the operating system. In the beginning, the OS allowed for various apps to be downloaded and installed (support was cut after the company went bankrupt). The app-installation process was seamless, comparable with today's Google Play, just earlier. The alarm clock app I used was perfect, with snooze, night dimming, always displaying accurate time (acquired from ntp time server). Other apps I installed showed photos from flickr, displayed RSS streams, played mp3s from USB stick; there was even a piano app that used the touch screen capabilities. Chumby was really a much cheaper alternative to a tablet, with a similarly great potential. Compared to a smart phone, Chumby's only missing feature was the GSM/GPRS, which I bet was considered to be added (since it has a microphone too). I also liked its stable shape, simple design and ease of use (great way to re-connect to the WiFi network too).

I never understood why it did not have a greater success.

My first impression on Cogwheel Nixie clock

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 under software control. So, like the Ice Tube Clock, in order to measure the high voltage and make sure the HV circuitry works, some software must be uploaded onto the processor. I expected the released software to do that. Unfortunately, the highest voltage I saw was under 9V.

After some digging (and learning in the process), I ended up with this simple sketch, adapted from Satashnik Nixie clock, which generates a stable 190V. I know, I was surprised too :)

#include "Arduino.h"

#define DDRHVPUMP  DDRB
#define BV2(a,b) (_BV(a)|_BV(b))
#define BV6(a,b,c,d,e,f) (_BV(a)|_BV(b)|_BV(c)|_BV(d)|_BV(e)|_BV(f))
#define VOLTAGE_WASTE   370                     //!< ~180V
#define VOLTAGE_SAVE    355                     //!< ~170V

volatile uint16_t voltage; 
static volatile uint16_t voltage_setpoint = VOLTAGE_WASTE;
static const uint16_t ocr1a_reload = 60;

void pump_init()
{
    // set fast pwm mode
    // COM1A1:0 = 10, clear oc1a on compare match, set at top
    // COM1B1:0 = 00, normal port operation
    // no FOC
    // WGM11:10 (WGM = Fast PWM, TOP=ICR1: 1110) = 11
    TCCR1A = BV2(COM1A1, WGM11);
    TCCR1B = BV2(WGM13,  WGM12);
    OCR1A = ocr1a_reload; 
    ICR1 = 170;
    TCCR1B |= _BV(CS10); // clk/1 (16MHz)
    DDRHVPUMP |= BV2(1,2);
}

void adc_init()
{
    voltage = 0;
    // PORTA.6 is the feedback input, AREF = AREF pin
    ADMUX = 6;  
    // ADC enable, autotrigger, interrupt enable, prescaler = 111 (divide by 32)
    ADCSRA = BV6(ADEN, ADATE, ADIE, ADPS2, ADPS1, ADPS0); 
    ADCSRA |= _BV(ADSC); 
}

/// Start voltage booster
void voltage_start()
{
    adc_init();
    pump_init();
}

ISR(ADC_vect)
{
    voltage = (voltage + ADC) / 2;
    if (voltage < voltage_setpoint) {
        OCR1A = ocr1a_reload;
    } else {
        OCR1A = 0;
    }
}

void setup()
{
    sei();
    voltage_start();        // start HV generation    
}

void loop()
{
  // clock functionality in here;
}

The next big step is to write the software to drive the tubes and actually show the time, which is essentially re-writing the Cogwheel Nixie clock code (or at least the basic functionality) from scratch. Then open source it. Any help would be appreciated :)