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Thermometer 2 board

A project log for Heroineclock II

Giant clock from a PIC18F6585, 135 cheap LEDs, foam core posterboard, hot glue, lots of hot glue

lion mclionheadlion mclionhead 08/07/2018 at 20:390 Comments

The 1st home etched board since February rolled off the assembly line. Phones & raspberri pi's have made this fabrication extremely rare.

Those PLCC 68's are still things of beauty & joys forever. Should have used a much smaller chip, but the 68's came 10 years ago & were never used. They were meant for building heroineclock II in through hole mode, but all through hole boards of that complexity were replaced by surface mount. It's totally pointless & expensive to use them now, outside of vanity designs. It'll be in full view of the apartment until the lion kingdom dies.

It occurred to the lion kingdom to make the segments fade on, instead of smashing on like LED brakelights.  It might make it easier to sleep & give it an edge over Chinese shit.  It would also feel like slowing down the aging process if the numbers didn't quickly change.

Would still have to bang the LEDs on when playing sound.  PWM needs to get above 200Hz.  The trick is fading slow enough to not wake up the lion, to not look like an incandescent light & yet fast enough to have a useful on time.  Having said that, sleeping is the only time a lion even sees the digits changing.  Once you get used to it, it doesn't matter.  

The https://hackaday.io/project/159267-moving-the-dvd-archive-to-an-8tb-hard-drive DVD archiving project yielded the original table for the original thermister.  20 years ago, you could obtain a bare thermister just by walking 2 miles, no shipping costs or 1 week delay.   30 years ago, someone who lived outside China even knew what a thermister was.

Useful range would be 5k - 30k.  Heroineclock 1 used a carefully tuned op-amp to span the entire ADC range.  Modern designs just wire the thermister in series with a resistor.  A 10k gives 0.45 - 3.75 on the voltage range.  A 5k resistor gives 0.83 - 4.29.

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