Over on his secondary YouTube channel, [Jeff Geerling] recently demoed the new Mitxela Precision Clock Mk IV.
This clock uses GPS to get the current time, but also your location so it can figure out what time zone you’re in and which daylight savings time might apply. On the back a blinking diode announces the arrival of each second. A temperature-compensated crystal oscillator (TCXO) is employed for accurate time-keeping.
The clock can be folded in half, thereby doubling as a clapperboard for movie makers. The dimming system is analog, not pulse width modulation (PWM), which means no visible flashing artifacts when recording. It is highly configurable and has USB connectivity. And it has not one but two ARM microcontrollers, an ARM STM32L476, and an ARM STM32L010. If you’re interested, you can pick one up for yourself from [Mitxela]’s shop.
Toward the end of his video [Jeff] does some navel gazing, thinking about what might be required if future versions of the clock wanted to get down into precision at the nanosecond level. Do you arrange it so the light arrives at the viewer’s eyeball at the right time? Or do you update it on the clock at the right time and let the viewer know about it after a minuscule delay? Philosophical preponderances for another day!
We should add that we’ve seen plenty of cool stuff from [Mitxela] before, including the Euroknob and these soldering tweezers.
Time is an illusion …. Lunchtime doubly so
Three microcontrollers? At lunchtime? (Yes, I know, it’s two uC’s, but the original quote is three pints…)
I’d highly recommend watching the video from Mitxela: https://www.youtube.com/watch?v=XL2cZjO5IUY
Or the detailed write-up on their website: https://mitxela.com/projects/precision_clock_mk_iv
Heh, and that was the main reason I made my video, I wanted more people to see Mitxela’s video (which seems to not have the amount of traction in YouTube’s algorithm I think it should! Though I’m a time nerd…).
M very first thought was I wonder are they using a dspll digital jitter attenuator. I guess I’ll click on the links to hopefully see a BOM (Bill of materials).
I guess that they have never heard of a clock jitter attenuator, so they are not using one which is used in devices like GPSDO precision frequency references by Leo Bodnar. You basically feed the jitter attenuator two or more clocks, one with excellent short term stability but weaker long term stability (TCXO), one with ok short term stability but fantastic long term stability (GPS TIMEPULSE can be configured from 1 Hz to 10 MHz on some modules) and both are used to discipline a DSPLL that will output a jitter attenuated clock
Such as the RC32504A? Interesting.
Can it also self-update if the time zone changes due to government rule? Michigan is trying to do away with springing and falling one hour every year by making us permanent EDT year round.
I cringe at any full automated timezone adjustments for this reason. Timezones are a political decision, some conventions aren’t strictly defined. (A few towns on border states/provinces shift their local time to match their more populous neighbours / trade partners).
If you’re obsessing over how long the GPS’s cable is, you may as well go on and take the distance from the display to the eyeball into account. And then figure out how to handle two users at different distances.
I wish he would get off clocks, its so time consuming
For maximum time-nerd cred, build one with a CSAC:
https://www.microchip.com/en-us/product/csac-sa45s
Looks like the SA.45 is obsolete, but they have the SA65 now:
https://www.digikey.com/en/products/detail/microchip-technology/090-02789-011/16555247
not sure on pricing, but the SA.45 was more than 5 grand per when I bought them a few years back.
I’m keen to make one of these. I hope he shares the gerbers and BOM soon. Thanks for bringing my attention to it. I am now a new youtube subscriber to your channel and his. Cheers!
Wait, the LEDs are dimmed by voltage? So basically the current is limiting by lowering voltage? That’s a strange approach, because LED voltage vs current is nonlinear.
Why not use a constant-current LED driver?
What am I missing here?