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C3Jr Build Instructions

We are so excited for you to build this advanced soldering kit!  The C3Jr is the smaller version of our ClockTHREE kit. It features mono-color LEDs instead of RGB full color. The LED matrix is smaller at 16 columns and 8 rows, giving a total of 128 addressable LEDs. Other than that, it is similar to the C3 in terms of build instructions. The SW code is also almost the same as that for C3. On the hardware side, we use a 8 bit row driver, instead of the dual 16 bit drivers used in the C3.

We have pointed out all of the tricky steps. (See Gotchas! below.)  Don't hesitate to contact us if you have any questions or if any issues arise.

  • Read through and understand the entire set of instructions before you get started.  I know, they always say that, but heed the advice this time.  It could save you hours of rework and much consternation.  We've captured all of the mistakes and blunders made in creating and building the prototypes and tried to foresee problems you may have.
  • Take your time.  Enjoy the build process and take a break when you feel fatigued.  You will have this clock for years to come (and hand it down to your grandchildren!) so there are no worries if it takes you an extra day or week to build it.
  • Leave the paper on the front cover and front frame until final assembly.  This protects the parts from scratching and smudging.
  • Soldering:
    • We assume that this is NOT your first soldering project. If it is, we'd suggest getting a cheap learn-to-solder kit to get started. If this is your first project in a while, here is a quick refresher on soldering. The main thing is to double and triple check that the part is in the correct place with the correct orientation (if applicable). While de-soldering is possible, it is troublesome and time consuming and risky. Make it a goal that you will not have to de-solder in the course of making this clock.
    • After each step, evaluate the solder joints from the front and back of the board. On the back, the solder should be shiny and make a volcano shape, as opposed to a dome shape. On the front, you should see that the solder came all the way trough the board.  If it doesn't look good, try re-heating the joint until the plated-through-hole sucks up the solder.
    • Check that the solder does not cause a short to neighboring parts.
    • If you do make a mistake, don't panic. Use a solder sucker to remove the solder and pull the piece gingerly while applying heat. If you damage a trace in the process of de-soldering, send a picture of the damaged area and we will help you make the most of the situation. It may be possible to "blue wire" around the damage.

  • The following parts will NOT be installed (not required)
    • C7 - 100nF RESET Capacitor
    • C11, C12 - 22nF (not used if X1 is a resonator, USED if X1 is a Crystal)
    • CD3 - 4 pin male header
    • J1, J2, J3 - Use any ONE of these three locations for Power In connector (USB-b)
    • P1 - 8 pin male header for 7 seg. display
    • P12 - V_OUT
    • P13 - ISP
    • P41 - STACK-L
    • P42 - STACK-R
    • rowBoB1 - 16 bit row driver

Gotchas! (repeated here for emphasis)

  • BEFORE YOU SOLDER the IC sockets check that every leg has come through the PCB.  Trust me, you don't want to  notice twenty pins in that a leg got bent.
  • Be careful with the baffles, they are fragile.