Eight digit, IN-18 clock is finished

[Mitch]

In addition to the extra tube and assorted parts, the 7805 used with the seven digit clocks was swapped out for a switching supply. Now everything is cool to the touch except for the Taylor edge supply, which is just slightly warm. Also, I added a nRF24L01+ RF module and 3.3v supply for it, on the right side of the board, two 4 pin headers for on-board GPS, one for Adafruit, and one for Ublox, and another phone jack to remotely mount the temperature sensor.

The software took much longer to develop than I had anticipated. With Carl's help the clock has the option to receive time from the Mod-6 repeater, in addition to GPS and on-board RTC only options. I thought about having GPS and repeater fall back to each other but that didn't seem to make much sense, so whichever one is selected will fall back to the RTC, with appropriate indicators.

Next I plan to design a four button remote control using ATiny or a similar processor, and another nRF24L01+ transciever, maybe even with some feedback. I'll also work on an eight digit version of the first clock that uses a variety of small tubes, adding RF to that one, too.

After that, I'd like to switch to Atmel Studio. Without the benefit of a debugger, this took far longer than it would have taken, had one been available. At that point I want to switch to a faster, 32 bit processor, as long as the libraries don't cause too many compatibility issues.  The 1284P was easy to add, with only a crystal and a couple caps. I'm not sure if the 32 bit processors are as simple to integrate.

That's about it.

https://drive.google.com/file/d/0B3kvk05blsPJQ0ttVlA3RWI3dDg/view?usp=sharing

[Mitch]

Link is a 9 second movie of the clock operating.

[Nicholas Stock]

That is some beautiful work! Congrats.

Any spare PCB's lying around? ;-)

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[Mitch]

Thanks. 

Yes, two extra, maybe three. You can have one for the cost of shipping. Please contact me off the group if you are interested.

 I'll post the code, schematic, and Diptrace files to Github, shortly. Only the seven digit design is there now.

Zev-2 seven digit nixie clock 

I forgot to mention that this version adds another menu to allow custom RGB color selection for each hour.

[gregebert]

Nice clock!

Curious about the capacitor you used for sustaining the DS3231 RTC during power-outages because there is a periodic temperature-compensation cycle every 64 seconds that takes a spike in current. Datasheet says about 600uA for up to 200msec, so each of those will take a bite out of your capacitor. If I did my math correctly, a 1000uF cap will drop around 120mV after each cycle.

In my case, I was monitoring standby current of my wristwatch (nominally < 2uA) with a 50uA mechanical meter, and the temp-comp cycle pegged the meter.

[Mitch]

Thanks!

I was not aware of that. I'm using a variety of supercaps bought from Digikey and on ebay. I didn't pay much attention to that part of the circuit or the values of the supercaps, but I was surprised to find that one clock had the correct time when not powered for about two weeks. 

[Greg P]

Nice clock Mitch.  Will you be offering a kit or the PCB for sale?  I'd like to get one but lack the chops for all this geek talk you guys are discussing.

[Mitch]

Thank you. I won't be selling anything, but the files and documentation will be on Github, for anyone interested. 

My projects are very easy to build, otherwise I would not be able to build them! Some kit building experience is required. There are no instructions, just a schematic and BOM. That's about it unless you want to dig into the code. I hope that at some point, someone with real C++ experience will go through it and comment. As it is, it works perfectly, and bugs are corrected as they are found.