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Clock/Calendar Project: The Schematics

Discussion in 'BoM Blogs' started by Blackthorne TA, Feb 10, 2013.

  1. Blackthorne TA

    Blackthorne TA Master in his Own Mind Staff Member ★ SPS Account Holder Adored Veteran Pillars of Eternity SP Immortalizer (for helping immortalize Sorcerer's Place in the game!) New Server Contributor [2012] (for helping Sorcerer's Place lease a new, more powerful server!) Torment: Tides of Numenera SP Immortalizer (for helping immortalize Sorcerer's Place in the game!)

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    The schematics for this project are much simpler than the USB DSO since there are really only three main components then a bunch of LEDs and a few connectors.

    Here is the main schematic that includes everything but the clock face LEDs:
    [PDF]https://dl.dropbox.com/u/66799035/ClockSchematic.pdf[/PDF]

    The brains are in the SoC labelled U3 which is the Cypress CY7C63823-SXC. It connects to the majority of the rest of the design since it is what is doing all of the controlling of the components and contains all the firmware I wrote.

    To the right of the SoC on the schematic are three connectors and four LED/resistor sets.

    The connector labelled J1 is the standard Cypress interface to the SoC to program it.

    The connector labelled J4 is the interface to the WWVB receiver that was extracted in a previous blog post.

    The connector labelled J5 is simply a power receptacle to receive the output from the wall-wart that will provide the 5V DC that the electronic components need.

    The four LEDs are there to indicate how well the WWVB signal is being received; the stronger the signal, the more LEDs will light (this is of course driven by the software in the SoC).

    To the left of the SoC on the schematic are the other two integrated circuits labelled U1 and U2.

    The component labelled U2 is the Maxim DS1307 Real Time Clock (RTC). As you can see the communication interface to the SoC is a very simple two-wire one which is the I2C serial interface. One additional interface is the SQW/OUT output from the RTC which will be the 1-second timing signal that prompts the SoC to update the clock display each second.

    And finally we have the Intersil ICM7228AIPI LED display decode/driver. It has an 8-bit data interface to the SoC (ID0-ID7) as well as a pair of control lines (WRITE Bar and MODE). The two connectors labelled J2 and J3 are the drivers for the LEDs. Since this was primarily designed to drive 7-segment displays the driver pins are labelled DIGIT1-DIGIT8 for the individual digits and SEGA-SEGG and D.P. for the segments of each display.

    Then there is the schematic for all 63 LEDs connected to the ICM7228 for the clock face display which you can see here:
    [PDF]https://dl.dropbox.com/u/66799035/ClockFaceSchematic.pdf[/PDF]
    Pretty straight forward interconnect as you can see.

    If you have any questions about the above, don't hesitate to ask; I'm happy to answer any question you may have.

    Next up is the PCB design!

    Hm. It appears there may be a problem with displaying the PDFs in the post at least for me. I hope that following the links below what should be the schematic pictures works for everyone.
     
  2. Dice

    Dice ★ SPS Account Holder Adored Veteran

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    Oh schematics , I like the way they look but I don't understand them. I wish I understood them because it looks kind of fun. Adding colour would make them into a nice piece of graphic art :p
     
  3. Blackthorne TA

    Blackthorne TA Master in his Own Mind Staff Member ★ SPS Account Holder Adored Veteran Pillars of Eternity SP Immortalizer (for helping immortalize Sorcerer's Place in the game!) New Server Contributor [2012] (for helping Sorcerer's Place lease a new, more powerful server!) Torment: Tides of Numenera SP Immortalizer (for helping immortalize Sorcerer's Place in the game!)

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    Ah, well if you have no electronics training at all that's understandable.

    Really all they are are design diagrams that show the individual components that make up the design and how they are all interconnected via circuitry to accomplish the goal of the overall design.

    Items labelled with "U" are integrated circuits and each pin on the sides of the box is an input/output of that device.

    Items labelled with a "J" are connectors; in other words circuit terminations that have specific shapes and sizes and may have specific assignments for each of the terminals.

    Items labelled with "C" are discrete passive components called capacitors which, for anyone not familiar, store electric charge.

    Items labelled with "R" are discrete passive components called resistors which, for anyone not familiar, resist electrical current flow and dissipate electrical energy as heat.

    Items labelled with "D" are diodes with conventional current flowing in the direction of the arrow only and blocked in the reverse direction. In the case of the diodes in this design, they are of the light-emitting kind which convert a portion of the energy flowing through them to visible light in the colors noted.

    Items labelled with "X" are crystals which are components that resonate at specific electric frequencies.

    The lines between all these components indicate how wires should be connected between them to complete the proper circuits.

    And I must say, it is fun! Otherwise why would I do it in my spare time? :)
     
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