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"Green" Gator Dot Clock




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              X            X             X         x AM/PM
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                      <Dot Clock>
 

Christmas time is approaching and also one member of our design team is turning 70, so we had to come up with a unique Arduino
(compatible) high tech, cool gift. We only had one day to construct this project.

We decided to "re-invent the clock" and came up with a retro desktop LED clock made from red, yellow and green very low power
LED's. The timebase we chose was the DS-3231 RTC, (ChronoDot from Macetech) which is good for +- 1 minute per year.
By having a Dot Clock with an accurate timebase and built-in DST, just set it, forget it and don't touch it
for 10 years! (Except for 8 years to change the Lithium battery and a minor time adjustment due to +- 1 min. per year error)

We made this clock clean. It has no ugly switches, buttons and manual adjustments. Everything is done by software.
The key to this design is to use an Arduino (compatible) microcontroller to control and compute the proper LED flash
patterns/sequences for displaying time.

  
We employed the Arduino compatible Rugged Circuits "Gator/Gator+" to drive the special Dot Clock display board.
The Gator's 28 I/O is more than ample for this project. The Gator/Gator+ has current limited I/O, ESD protected IO and over
voltage protected I/O. Using the Gator's "exposed electronics" made it perfect for the "high tech look" for this project
along with the USB power sourcing and the secure spring loaded phoenix terminal blocks.

The operation is simple.
The "Dot Clock" unit of displayed time is every five minutes as opposed to every minute and second on a standard wall clock.
You will never be late with this "Dot Clock" because the time is rounded UP to the nearest 5 minutes.

Operation description:
The "short hand" hours segment always flashes. (yellow "short hand" hour segment with 2 series LED)
The "long hand" minute (5 minute) always stays on steady. (yellow "long hand" minute segment with 2 series LED)
The clock display diameter indicates the hours and elapse minute increments rounded UP to the nearest 5 minutes.
Red LEDs are placed at 12,3,6,& 9 o'clock plus a red LED the center. Green LED's are placed at 1,2,4,5,7,8,10,& 11,
which makes the dot clock easy to read from distances far away. Also, there is a AM/PM red status LED near 3 to 4 o'clock.

Dot Clock Display time examples and operation:
 
#1. If both the minutes and hours are the same - at 3 and 15 minutes after the hour. Segment 3 will be
flashing at a much higher rate of speed than normal slow flash of the hour hand.

#2. If the "long" minute segment is on steady at 50 minutes and the "short hand" hour segment is "slow" flashing at
segment 2, then the time is 10 minutes till 2 NOT 2:50 OR NOT 50 minutes after 2 or NOT 10 minutes till 3 o'clock!
Since, on a standard wall clock, you can see the hour's hand move progressively towards the next hour, you cannot see
this impending time change on the "Dot Clock". We created a mid-hour correction factor. At halve past the hour, the
hour hand or segment jumps/increases by one hour and all dot clock readings are read "Till the hour". (after mid-hour)  
Stated another way, the time reads 5, 10, 15, 20, 25, 30 "AFTER" the hour and then jumps 1 hour ahead at mid hour and
then the "Dot Clock" display readings are all 25,20,15,10,5 "TILL" the hour. Worst case, you could read it wrong and
be 1 hour early but you will never be late!

#3. The AM/PM turns on exactly when it is "PM" and off when "AM".

#4. On the back of the Gator there is the built-in pin 13 red LED which flashes every 500 ms.

#5. The AM/PM status indicator toggles every 1 minute. (For calibration checking)

The 5 minute rounding calculation goes as follows: If the minutes are between 1-4 minutes the time is rounded up to the
next 5 minute "even" increment.  

Daylight savings time "spring forward" and "fall back" times are adjusted automatically through "C" code
pre-programmed in the software. (We only decided to program ten years of DST due to the US government's constant
updates and changes - the last government update was 2007)

The Dot Clock 5 VDC power is derived from any USB port @ 100 ma or a wall AC/USB wall cube. (~70ma current draw)
  
A built-in terminal monitor program, was created for diagnostics and reading & setting times/dates. Rugged Circuit's
FREE GUI terminal program or MS PC Hyper-Terminal can be used with the built-in monitor program.(38,400 8,N,1)
Note: Warning ... use of the Arduino serial monitor built-in to the IDE, does NOT have a carriage return appended to each chr/string entered. (As of rev. 17 ... but this might change soon!)
Note: Even if the dot clock display ceases to function, the dot clock exact internal time base can still be viewed using a
terminal program along with the built-in monitor routines.
      
Since the Rugged Circuits Gator 324P has another (second) hardware serial port "built-in", we also decided to use the Dot Clock
as a precision internal timebase for our the network timebase on our LIN Bus in our home automation, security and
on our contract development systems.

Pictures (below)
« Last Edit: September 28, 2009, 01:20:13 pm by ArduinoAndy » Logged

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Please Note:
The rubber bands are holding the front acrylic cover on until the super magnets arrive for installation.
A hole was drilled into the back so a wooden plunger could contact the reset tac switch for uploading.
The ChronoDot DS-3231 RTC is sandwich between the Gator and Dot Display PCB.
 8-) 8-) 8-)

« Last Edit: September 28, 2009, 06:32:43 pm by ArduinoAndy » Logged

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I love it! Excellent concept and great construction on the PCB and case. Good to see the ChronoDot put to use, too!
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What a great project! Amazing, too, that it was a one-day design.
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Quote
Amazing, too, that it was a one-day design.

It took many hours on the deck drinking "liquid refreshments" to come up with a general design spec. (See below)

It took three team members to design it. Printed circuit board design, enclosure/mechanical and software sketch.
The design of the printed circut board took 1/2 day and we waited 5 days to receive it from ExpressPCB.
In the mean time, it took only 3 days for parts from Digikey and only one day to construct/assemble this project.
Software debugging is an ongoing process - so far there are no major bugs.
 

"Green" Gator Dot Clock General Design Specs:

1.  1 day for board construction, enclosure assembly and software testing.
2.  Green - very low power operation. (All T1 3 mm LEDs have a 2 ma current draw each)
3.  Reliable and accurate - see timebase options below.
4.  We decided to employ the Arduino compatible Rugged Circuits "Gator" to drive the special dot clock display board.
    The Gator's 28 I/O is more than ample for this project. It has current limited I/O, ESD protected IO and over voltage
    protected I/O. Using the Gator's "exposed electronics" made it perfect for the "high tech look" for this project along with
    the USB power sourcing and the secure spring loaded phoenix terminal blocks.
5.  All passive display components - no IC drivers/multiplexors/port expanders.
6.  The clock timebase that was chosen (below) was the DS-3231 - "Chronodot" by Macetech $14 <-- "The Industry's most accurate RTC" by Maxim Semiconductor.  
    
    Timebase design options:
      A. 60 HZ power line with microcontroller decode <---- not accurate.
      B. Caller-ID using modem decoding <---- expensive plus caller-ID service is required.
      C. PC clock with serial updating (Python script) <--- not practical for standalone operation.
      D. NTP Network / Server with Ethernet time update <----- very expensive and not practical for standalone operation.
      E. GPS NEMA decode <---- expensive & un-reliable and won't work in older homes with chicken wire plaster and even new homes with high ambient noise.
      F. Software Real Time Clock <--- not accurate & un-reliable due to Arduino time base crystal and having a reset causes the clock to be adjusted again.
      G. WWVB C-Max decode <--- expensive and un-reliable and won't work in older homes with chicken wire plaster and even newer homes with high ambient noise.
      H. Local hardware I2C timebase with Lithium battery backup ~ 8-10 years.
         1. DS1307 I2C realtime clock with -+ 2 minutes per "month" accuracy <---- Used in first beta prototype ~$5 from Futurlec & $20 from Sparkfun.
         2. DS3231 I2C realtime clock with _+ 1 minute per "year" accuracy   <---- Used in final design - drop in replacement (register wise/ address ).  

7.  Simple to operate and no pushbuttons. The clock is re-calibrated by uploading the proper time via program sketch or serial terminal monitor routine.
    The daylight savings time and "spring foward and fall back" 1 hour adjustments are done automatically in software. This dot clock time display readings should be
    good for 10 years with no manual user inter-action. (10 years of daylight savings dates were programmed into this clock)
    The US government changed again the DST dates in 2007 and a lot of digital clock manufacturers were stuck with the wrong switchover DST dates in their "fixed clock" design.
    By using this computer controlled programmable clock this would never happen!  
8.  Clock display is always fast by design (1-4 mins). Limited I/O and LED board placement which prevented from showing the minutes and hour offset.
9.  Make the dot clock "unique" and as high tech gift which cannot be purchased anywhere.
10. Wiring from all electronic modules must be organized and neat due to the acrylic enclosure.
11. Use low cost "dot" display components. (< $8.00) <<<<<<<<<<<<
12. No surface mount components on the clock dot display printed circuit board.
13. No prototyping - this design is extremely simple. (In fact, the display board could even be constructed on a perf board or Arduino shield.)
14. Piggy back mount all modules with standoffs. The dot display, DS1307/DS3231 RTC, the front panel clock faceplace, and the Gator mounting
    are all to be mounted together as on integral unit for the high tech display look in the highly polished acrylic enclosure.    
15. Use a highly polished acrylic enclosure and clock stand. (Acrylic jewelry box and plate stand from The Container Store)
    No user physical contact with the electronics will be allowed even though the Gator has all I/O ESD protected and is almost indestructable.
16. Make the dot clock design so the dot clock can drive a custom designed "future" 3D laser engraved block of crystal (glass). <--- very expensive but cool.
17. Design a "optional" clock faceplace for the dot clock. <--- not really needed due to high vendor cost and use of multi-color LEDs.          
18. Cast the dot clock display in plastic resin which includes the front dot display and faceplate for the high tech design look. (In the future)

    Note: Casting in plastic resin is an art form in its self. The casting temperature, humidity, curing time, curing catalyst,
    resin mixing and pouring procedures are all critical for a proper water clear glass like cool look.
    Embedding the electronics in resin won't occur until the electronics are "burned in" and the LED lighting is at a
    constant MCD intensity. Having just one LED burn out renders the whole resin casting and dot clock almost useless!
19. No extra power supply and low power green operation for USB < 100 ma. (Power came out to 70ma)

 8-) 8-) 8-)
« Last Edit: September 28, 2009, 04:36:59 pm by ArduinoAndy » Logged

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