Revisiting IceTube clock designs and construction, after performing some small repairs on an IceTube clock I built back in 2010.
After replacing a power supply filter capacitor and improving the heatsink on the TO-220 5 volt regulator, on a clock I built in 2010. I decided to revisit the design to see what improvements I could make after 10 years.
The original IceTube clock was designed by Limor “Ladyada” Fried of Adafruit. There are several other similar designs with different enclosures, but this one was the most popular, as it was developed as a kit by Adafruit. Over the first few years there were many firmware and hardware updates of the original design, such as GPS synchronization, auto dimming, and improved firmware.
My original clock with auto dimming was a version 1.1 and I ended up building 12 of them for Christmas presents that year.
I had held on to a second 3D printed enclosure that I had printed 9 years ago, that was designed by Nathan Matsuda (NMATSUDA) and shared on Thingiverse. It was designed for the original version 1.0 board, but had some very restrictive height issues. The enclosure was printed on a Z Corp. Spectrum Z‑510 powder 3D printer, and then impregnated with an epoxy resin to improve it’s strength.
While the main and side circuit boards were functional as originally designed, I thought that there were several areas that could use some improvement. Most of the original power traces were between 16 and 10 mil width, and the 5 volt TO-220 regulator was dissipating quite a bit of heat.
I greatly improved the ground plane and increased the size on all of the power traces, and most of the other circuit traces on the board. I also modified the board to use a switching voltage regulator for the 9 volt to 5 volt supply along with improved input and output filtering to reduce ripple voltage.
I had several of the Maxim Integrated DS32kHz dip versions of their temperature-compensated crystal oscillator (TCXO) module with an output frequency of 32.768kHz. So I decided to put together a small circuit board that would fit into the unused enclosure end near the 9V power jack. The board breaks out the 5V, ground, 32 kHz signal pins, provides a 1220 battery holder, and ties all the unused pins to ground as required in the datasheet.
This board replaces the 32.768 kHz crystal, and two load capacitors on the main board and provides an accuracy of ±1 Minute/Year from 0°C to +40°C.
The 32kHz output pin of the board is connected with a shielded twinax cable conductor to pin 9 (PB6 / XTAL1) of the ATmega328P microcontroller using the existing empty crystal connection. The ground pin on the DS32kHz board is connected to the main board using the second twinax conductor to one of the empty load capacitor ground connections, and the twinax shield is connected only to the second load capacitor ground connection. There is no connection of the twinax shield to the DS32kHz board. The 5 volt input on the DS32kHz board is connected to the 5 volt regulated output of IC3.
I also removed the ISP connector on the main board to make room for the additional power supply filtering. My ATMEGA328P is socketed and fairly easy to remove for reprogramming so I decided it was a good trade-off.
My original firmware was assembled by DigiSage on the Adafruit forums and included several fixes and mods by himself and others such as a seconds display mod, reset issue fix, clock calibration menu, and photoresistor auto-dim.
For the version 1.31 clock I used a newer version of firmware by jarchie also from the Adafruit forums. The XMAS-Icetube firmware can be compiled for use on the original version 1.1 boards, or jarchie’s updated Rev. D hardware boards. (Next Project)
I was able to find some low profile capacitors by Nichicon that would fit the limited height of the enclosure and finished assembling the main board.
The IV-18 VFD tubes were purchased on Ebay from a seller in Russia with a three week shipping time, but arrived in excellent condition.
I painted the enclosure with “Krylon” Metalic Oil Rubbed Bronze paint, and attached the endcaps with Black-oxide M4 * 0.7mm * 25mm socket head screws.
Since this was a specialized one-of-a-kind build, I will not be providing a BOM, but all updated components are listed in the EagleCAD schematics.
After finishing this build I decided to build some more IceTube clocks as gifts using jarchie’s updated Rev D hardware as a starting point for the new design. (Coming soon…)
Icetube Clock Enclosure by nmatsuda on Thingiverse
Icetube Clock Enclosure by nmatsuda on Shapeways
EagleCAD schematic and board IceTube clock files for Version 1.31
EagleCAD schematic and board DS32kHz files Version 1.0
jarchie Xmas-IceTube-firmware source files
Adafruit build tutorial for Ice Tube Clock V1.1