LUNCHTIME CLOCK JAMECO PART NO. 2169512 Have you ever wished lunchtime were longer? Well, wish no longer! Thanks to advances in technology, I present to you a clock that speeds up 20% every day at 11:00 and slows down 20% every day at 11:48. Now you ll have an extra twelve minutes of lunch to enjoy. Twelve minutes may not seem like a lot but, to put it into perspective, this is a full additional hour of lunchtime gained every week. Experience Level: Intermediate Time Required: 3-6 hours Required tools and parts: Soldering Iron and solder Computer for programming Wall Clock Adafruit Real Time Clock Breakout Board kit: https://www.adafruit.com/products/264 Bill of Materials: Quantity Jameco SKU Component Name 1 51262 7805T Voltage Regulator 1 198791 9V Battery 1 325139 16MHz Crystal 2 254801 BC547B NPN Transistor 2 15405 22pF Capacitor 1 112300 28-Pin IC Socket 10 2157159 1kΩ Resistor 1 1949488 9V Battery Snap 1 2129334 ATmega328P Microcontroller IC 1 2144614 1x6 Position Pass-Through Header 1 2151486 Arduino Uno R3 Microcontroller Board 2 2169521 BC557CG PNP Transistor 1 105111 2.4" x 3.4" Protoboard
Step 1 Remove the Clock Movement Pieces Remove the clock movement from the clock body. This will require removing the front glass face from the clock as well as the clock's hands. Be careful, you will have to reassemble everything so you don t want to break anything. Step 3: Hack the Movement Pieces Inside the clock movement is a single coil stepper motor. We want to disconnect the coil from the clock's timing circuit and attach wires to the coil so that we can control it ourselves. Open up the clock movement and make careful note of where everything is (or take a picture). Take apart the movement until the circuit board is free. Locate the contacts on the circuit board where the motor is located. You will notice that these two contacts have traces that go off to the chip. Use a razor blade or knife to scratch away at these traces until the connection with the chip is visibly broken. For good measure, cut away the timing crystal, rendering the circuit more or less useless. Solder about 6" of wire to each of the motor terminals. When this is done put the whole thing back together. If there isn t a spot in the case where you can conveniently slip the wires through you may have to cut a small hole for the wires to pass through.
Step 4: Putting the Clock Back Together Once the movement is good and hacked, put the clock back together. Make sure that the hour, minute and second hand all lined up at 12:00. It will not work properly if not. Step 5: Real Time Clock Kit Put together your Adafruit DS1307 Real Time Clock Kit. Need help use this link: http://www.instructables.com/id/assemble-an-adafruit-ds1307-real-time-clock-kit/ Set the time on the RTC board. As long as you don't take the battery out, you should only need to do this once (at least for the next five years or so until the battery dies). In-depth instructions for setting the time use this link:
http://www.ladyada.net/learn/breakoutplus/ds1307rtc.html Step 6: Building the Circuit The circuit is pretty simple to build. It is basically what people are calling a "hackduino," a socket for the real time clock board and a crude H-bridge to control the motor.
Step 7: Program the Chip You will need to install the RTClib library for your code to work. Use this link for instructions: http://www.ladyada.net/learn/breakoutplus/ds1307rtc.html Download lunchtime_clock.zip, uncompress it and then upload the lunchtime_clock.pde code onto your chip. Here is the code: // Lunchtime Clock // by Randy Sarafan // // Slows down 20% at 11 and speeds up 20% at 11:48 until it hits 1. // The rest of the time the clock goes at normal speed // // Do what you want with this code. Just make certain that whatever you do, it is awesome. // #include <Wire.h> #include "RTClib.h" RTC_DS1307 RTC; int clockpin = 9; int clockpin1 = 10; void setup () { Serial.begin(57600); Wire.begin(); RTC.begin(); void loop () { DateTime now = RTC.now(); TurnTurnTurn(1000); if (now.hour() == 11) { for (int i = 0; i < 1800; i++) { TurnTurnTurn(800); for (int i = 0; i < 1800; i++) { TurnTurnTurn(1200); int TurnTurnTurn(int TimeToWait){ analogwrite(clockpin, 0); analogwrite(clockpin1, 124); // sets the value (range from 0 to 255) delay(timetowait); analogwrite(clockpin, 124); analogwrite(clockpin1, 0); delay(timetowait);
Step 8: Putting it all Together Once everything is programmed you can transfer your ATmega168 chip from the Arduino to your circuit board. Simply plug in your RTC board into the socket and make sure the pins are lined up correctly before powering it up. Go ahead and attach the circuit board and battery to the back of the clock. You can use hot glue, gaffers tape, even self-adhesive Velcro.
Step 9: Synchronize the Clocks Put a new ATmega168 chip into the Arduino. Connect the Arduino to the RTC board. Run the sample code using this link: http://www.ladyada.net/learn/breakoutplus/ds1307rtc.html Open the serial monitor. The time displayed here is the time you are going to want to sync your clock to. It was easiest to set a third clock (I used my computer clock) to be perfectly in sync with the RTC board. Then, I powered down the Arduino, transferred the RTC board back to my circuit and set the Lunchtime Clock to a minute later than my computer time. At just the right moment, when the minute changed on my computer, I powered up the lunchtime clock to achieve synchronicity.