原创 Cool chronograph inspired by 1960s Mustang

As an aside, the guys and gals at Alorium are the ones who created the XLR8 ("accelerate," get it?). This little scamp is a drop-in replacement for a regular Arduino Uno -- same footprint, same connectors, same clock frequency, etc. The difference being that it also contains hardware accelerator blocks that can significantly improve the performance of things like floating-point math and dramatically improve the accuracy of tasks like servo control.

XLR8 FPGA-based Arduino Uno clone (Source: Alorium Technology)

 

The XLR8 made one of its first public appearances at ESC Minneapolis 2015, but let's not wander off into the weeds here...

In his email, Stephen said: "I've very much enjoyed your writings about your Cunning Chronograph project and I’d like to share with you my own clock. As you can see in this video, the design inspiration is a 1960s Ford Mustang dashboard."

Stephen went on to say that the guts of his clock include:

- An Arduino Uno.

- A ChronoDot real-time clock (RTC) with a temperature compensated oscillator that communicates with the Arduino via I2C.

- A pair of small stepper motors that are commonly used in automotive speedometers (these steppers are small enough to be driven directly by the Arduino's digital outputs.

Well, this immediately reminded me of my other ongoing timepiece project -- the Vetinari Clock. Unlike Stephen, I'm using antique analog meters, but the overall concept is much the same.

Vetinari Clock prototype (Source: Max Maxfield / EETimes.com)

 

I do like the way Stephen has illuminated his hours and minutes displays; I wish I'd done something like this with my Vetinari Clock; maybe on the next revision after I finish this one (and the Inamorata Prognostication Engine, and the Caveman Diorama, and the... LOL).

Stephen also sent me the following image of the insides of his clock, saying: "On the bottom of the case, mostly obscured, is an Arduino Uno. Through the back there is access for the 9V power input and the USB port. The perfboards on the back of the dials contain an automotive stepper motor (Switec X25.168) and a bunch of diodes to clamp voltages between the rails. The diodes protect the Uno, which is directly driving the steppers. Hanging off the side of the minute-side perfboard is a “ChronoDot” real-time clock module with a temperature compensated oscillator. This communicates with the Uno via the I2C bus."

Inside the Ford Mustang-inspired clock (Source: Stephen Fraleigh)

 

Stephen went on to say: "The ChronoDot was a late addition. My first stab at the clock just used a timer interrupt based on the Uno onboard oscillator, but that didn’t keep good time at all. The Uno clock wasn’t spec’d with the accuracy that I want. (Or maybe my software was to blame, but that can’t happen, right?) With the ChronoDot upgrade, not only do I get accuracy within one minute per year, but now I have battery backup."

I'm using the same ChronoDot module as Stephen, which leads us to the fact that we just moved to Daylight Saving Time. I hadn't even thought about this until I went into work yesterday and realized that my Cunning Chronograph was an hour off.

I mentioned this to Stephen, who responded by saying: "I don’t have a summer time change feature on my clock, either. With the ChronoDot being accurate to within one minute in a year, it would be nice if I didn’t have to fully reset the time every six months. On the other hand, it’s fun punching the buttons and watching the hands move!"

Hmmm, my chum Steve Manley in England is also making a Cunning Chronograph, I wonder if he's thought about this. It may be that he hasn’t run across this problem yet, because they don't transition into Daylight Saving Time until a week this coming Sunday (March 27) in the UK.

What we need is an auspicious algorithm to address this sort of thing. In fact, I just posted a column about this very thing. I'm planning on making this into a little coding competition, with the most capriciously cunning solution being the one I'll incorporate in my Cunning Chronograph. Maybe you have some ideas you'd care to share...