Introduction: Pong Clock
March 2014 Update! Version 5.1 of the code is out with bug fixes and a nice lower case font. Get it while it's hot! The link is on the last page of this instructable!
This clock uses the classic video game Pong to tell the time. The 2 players automatically win and lose so their scores show the hours and minutes. It's not too hard to build and should cost less than $100. All the parts are easily available on eBay and the software code is free to download!
The clock can also show the time written in words such as "Ten Past Twelve", with large or small digits and with a slide or jumble effect. The date pops up every now and again too, printed out with a retro flashing cursor effect. A menu screen lets you choose the display mode, or you can have the clock pick a random mode every few hours.
The project uses 2 bright LED matrix panels fromSure Electronics. You can buy them in red or green with either 3mm or 5mm LEDs. An Arduinoruns the main code and a DS1307 clock chip keeps time, even when the power is off.
Step 1: Parts List & Cost
So here's what you need...
2 x Model 2416 Red or Green LED Matrix Displays from Sure Electronics
You can get these from Sure's eBay store for $15 each: http://www.sure-electronics.net/ Make sure you get the new version of the display which is based on the Holtek HT1632C chip. You can tell the new displays as they have the controller chip and DIP switches on the back. (See pic). My clock is made with the 3mm LED display, but they also make a larger 5mm one.
1 x Arduino Uno / Duemilanove with ATmega 328 CPU
Th Arduino is the brains of the clock. It has a microprocessor that runs the main clock software, plus inputs and outputs we connect to the displays and other components. Ensure you get an Arduino with the ATmega 328 CPU. (Some older boards come with the ATmega 168 with doesn't have enough RAM). You can get Arduino's for about $30. Try Sparkfun Electronics or eBay.
1 x DS1307 Real Time Clock chip (RTC) and IC socket.
1 x Crystal Oscillator for the DS1307
1x 3.3v Coin Cell and holder - battery backup for the DS1307
I found all these bits on eBay bundled as a kit for $10.
1x Arduino Prototyping Shield
The prototyping board or ‘shield’ plugs onto the top of the Arduino making it easy to add components. It brings all the Arduino's input and output pins onto a circuit board that you can solder components to. Get a board which is designed for a chip to go on, i.e. one that brings each pin of the IC out to a solder pad you can connect wires to (see pic). Again places like Sparkfun or eBay are good sources for them. You should be able to pick one up for $15 - $20. If you don't like the idea of soldering, you could get a breadboard and jumper wire to build the circuit on temporarily instead.
1x 16 Pin IDC Socket
We solder this socket to the prototype board so we can plug the display ribbon cable in. They are a couple of dollars on eBay. If you aren't planning to solder, you don't need this.
2x ‘Push to Make’ Buttons.
These are used to set the time / change the display mode. You can get them for a few dollars.
1x USB Lead - Type "A to B"
This is needed to to program the Arduino, and then as a power lead for the clock.
1x Mains to USB Power Adapter
This is used to power the clock and you can pick them up for less than $10. Look for one with an output of 150mA or above.
Step 2: Circuit Diagram
This diagram shows how to connect the parts. It's not too difficult, and you can try it on a breadboard first to make sure all is working. When you are happy you can solder the parts to the prototype shield.
IMPORTANT NOTES!
1)The 2 push buttons are not shown in the above diagram. You will need to connect one button between Arduino digital pin 2 and GND. The other button needs to go between Arduino digital pin 3 and GND. The digital pins are the ones that don't start with the letter 'A'.
2) The pin layout on the DS1307 on the diagram is not exact, pin 8 should really be top right opposite pin 1. All the pin numbers are correct in terms of what they connect to however, so follow the numbering and you should be fine.
Step 3: Connecting the Displays
The displays use a serial protocol called SPI to receive data. There are only 4 wires needed between the Arduino and the first LEDdisplay. Two more wires are required for power.
You'll notice each display has 2 connectors on the back. These are for daisy chaining multiple units together as we are doing, and it's what the little ribbon cable in the box is for. Connect the displays together using the ribbon cable. You can use either connector on the back, they are the same.
Use one of the free connectors on either display to connect to the Arduino. Again it doesn't matter which one. For testing purposes I poked jumper wires from the Arduino into the ribbon cable. When I was happy things were working, I soldered the IDC socket to the prototype shield, meaning I could plug the ribbon cable in.
Pins 4 and 5 on the Arduino need to connect to pins 1 and 2 on the display connector respectively. These are used for something called Cable Select or 'CS'. Cable Select determines which display listens when the Arduino is sending data out. The displays have small DIP switches to set their cable select address – essentially giving them different identities. Set one display's switch to have CS1 on , and the other to have CS2 on .
Pin 10 on the Arduino is used to send the actual display data, and connects to pin 7 on the display. Pin 11 on the Arduino sends a clock signal. Connect this to pin 5 on the display.
Finally connect pin 12 on the display connector to positive and pin 11 to GND. Alternatively if you prefer you can use the screw terminals on the back of the display for power.
Step 4: Connecting the Clock Chip
The DS1307 clock chip keeps the time. It uses the I2C protocol and only needs 2 wires to send time data to the Arduino.
Connect pins 5 and 6 from the DS1307 to Arduino pins A4 and A5.
Connect the crystal between pins 1 and 2 on the DS1307. The crystal regulates the clock and can be connected either way round.
Finally the coin cell battery’s positive terminal connects to pin 3 on the DS1307 and the negative terminal connects to GND . The battery runs the clock chip if the power is turned off meaning you don't have to reset the time. It should last for many years.
Step 5: Connecting the Buttons
Connect one push button between Arduino pin 2 and GND , the other between Arduino pin 3 and GND.
Step 6: Connecting the Power Supply
Connect the 5v and GND lines from the displays to the Arduino’s 5v and GND pins. Do the same for the 5v and GND pins from the DS1307 clock chip. We are going to supply power via the Arduino's USB port using a mains to USB adaptor.
A FEW WORDS OF CAUTION WITH THE POWER!
1) Don’t use a higher voltage supply into the Arduino’s round power jack. The onboard regulator may not be able to cope with the power demand. If you try you'll notice the Arduino will get very hot very quickly and probably not last too long!
2) Be very careful if you are powering the Arduino from a computer’s USB port. You could easily damage the port if you have a connection wrong or if the computer can’t supply enough juice. I powered my setup with my Macbook for testing and all was well, but be warned! Use the USB adapter anytime the displays are plugged in to be safe.
Step 7: About the Prototyping Board
The Prototyping boards or ‘shield’ plugs into the Arduino making it easy to add components. On a standard prototyping board you should have room to solder the DS1307 clock, crystal, battery and the IDC socket for the display ribbon cable. I attached the 2 buttons with wire, but you could solder them direct to the board.
I can’t really give instructions for what to solder where, as prototyping boards vary quite a bit depending on what you buy, but you should be able to figure it out based on the circuit diagram.
When things are soldered it should look something like mine in the picture. You can see the IDC plug on the right for the display cable, in the middle is the DS1307 clock chip. The tiny silver capsule above the chip is the crystal. On the left is the coin cell to keep the time if the power is lost. The red button top right on the board is a reset button which came in the pack with the shield. It's useful as the shield covers up the reset button on the Arduino itself.
Step 8: All Connected!
Here you see everything connected together. The 2 displays plug into the prototyping board which sits on top of the Arduino. Easy!
Step 9: Uploading the Clock Code
http://www.arduino.cc/en/Main/software
Once that's installed, download the zip fie containing the clock code from Dropbox here: https://www.dropbox.com/s/mh8qzsms8gl3f34/pongclock5.1.zip
Unzip the file. Inside you will see themain clock sketchcalled pongclock5_0.ino and 4 library folderscalled 'Button', 'RTClib', 'Font' and 'ht1632c'. These libraries are extra bits of code needed by the main clock sketch.
Next install the libraries. When you installed the Arduino software it should have created a folder somewhere for your sketches (i.e. projects) to go in. Find that folder and see if there is a folder called libraries inside. If there isn't, create one. Then copy the 4 library folders from the zip into this libraries folder. After you have done that make sure you quit and restart the Arduino IDE to make it pick up the new libraries.
After restarting, go to the Sketch -> Import Library menu. If the libraries are in the right place you should see their 4 names listed in this menu.
Now go to the File menu and open the main pongclock sketch. It ends in .ino. You should see the code appear in the main window. Next pick your Arduino Board Type in the Tools -> Board menu, then hit the Verify (check mark) icon. The compile test should compete without errors.
Time to upload the code to your Arduino! Unplug the Arduino from the clock prototyping shield and plug it into your computer with the USB cable. Click upload and wait for the code to be uploaded. Watch the TX and RX LED's on the Arduino flash for signs of data transfer.
Finally unplug the Arduino from the computer and plug it back into the prototyping shield. Then plug the USB lead from the Arduino into the USB to mains adapter.
All being well the display's should spring to life. Use the buttons to set the time and then sit back and admire your handiwork!
And if you really like the project you can tip me in bitcoin to this address! 1JPdDk4DiKYDsjTYghHatJp1FFQsv6bpEv
Troubleshooting
I get an error compiling:
- Check the libraries are installed and appear in the menu.
- Check you have Arduino software version 1.0.5.
- Check your board type and serial are set correctly in the Tools menu.
- Check your arduno has 32K RAM or more.
- Normally a wiring issue. Check the LED on Pin 13 or the Arduino flashes. If not then the clock chip is not being read. Check your connections to the DS1307.
- You must have a battery connected for the DS1307 to work.
- Check your wiring to the ribbon cables and check the display is getting enough power.
- Check the DIP switch settings on the displays are as per the instructions.
Thanks
Thanks to everyone who contributed, including WestFW on the Arduino forum for providing the initial driver code, SuperTech-IT for the dimming and 12 hour mode, Alexandre Suter for help with the conversion to Arduino 1.0 & Kirby Heintzelman for all the testing!

Runner Up in the
Clocks Challenge
101 Comments
5 years ago
Adafruit sells similar LED panels with the HT1632C but they only have 10 pin connectors. They also sell a preassembled DS1307 clock module. Do you think this will cause issues with the code? Sorry I'm new to this I hope I gave enough info.
https://www.adafruit.com/product/555
https://www.adafruit.com/product/3296
Reply 5 years ago
Yeah those look like they would work. You will need a battery for the clock. The pin numbers may be different to what I have in the instructable though so you would need to figure out what is what in them
Reply 5 years ago
Any idea how I will be choosing the correct CS options on the Adafruit panels? These panels don't have the switches on them like the Sure Electronics ones do.
Reply 5 years ago
Hmm, they seem to say you just fill solder jumper j5. But you would need to check what their code is doing to see if it's the same. To be certain of it working buy the displays i mention in the instructable.
Reply 5 years ago
Thank you. I'm gonna give it a shot.
7 years ago
Hi folk
a question , you can't play (Pong ) it's playing automatically ?
claude
Reply 7 years ago
It plays automatically and every minute a player looses to reflect a change in the clock. Clever!
7 years ago
thumbs up both hands indeed. Will this work if I use digispark USB attiny 85 ?
7 years ago
Hi again.
Worked it all out for myself.
Works great.
Stuart Smith
7 years ago
Hello, I was wondering if this clock can be made using a 32 X 64 RGB LED Matrix Board such as can be purchased from AdaFruit? it would make the display portion easier and construction simpler.
7 years ago
Hi there. I have built this clock. It works great apart from not being able to set the time and change any of the controls. As the curser will not move using the two buttons. It will go through all of the menus. It just will not allow me to move the curser in order to choose a menu. Hence; Unable to move into settings?
Please could you advise me on what to do. I am using version 1.0.5 and a cheap uno board. And I am using a pre-built DS3231 RTC AT24C32 12C Precision Real Time Clock & Memory Module. (Bought off ebay) Does this RTC need extra software. It does keep the time on the pong board? There is nothing wrong when I verify the software and it uploads without any problems.
I thank you for your time.
Stuart Smith.
8 years ago on Introduction
Hey, so i am going to build this (already have most of the parts.) but i have minimal experience with bread boards and doing this stuff. any Ideas where to go to learn? like videos?
8 years ago on Introduction
Can someone help me to work with sure electronics 32x8 green led module to run as a simple clock.
8 years ago on Introduction
8 years ago on Introduction
This was my first project !
Thank you so much for a simple, fun to make and awesome project !
The included photos are of the prototyping stage. I am still muddling over if I should make it permanent or make other projects using the existing parts. I also made a small update to the 5.1 code using the 5.1 FR code which saved the settings to the RTC.
I also changed the RTC to use a DS3231, which required no changes to the code.
Hats off to everyone who contributed. You have made me day/week !
8 years ago on Introduction
Hi,
Thanks so much for the instructable! I've built one and it looked great. However after a month or so after I had left it unplugged and unused as I had traveled, I returned home to a non-functioning clock. The displays do not light up and I've tried using another arduino and ds1307 board I had on hand with no luck. This has been confusing me since before I left, the clock had worked as intended yet now fails to do so. I've checked all the wiring yet I still don't know what to do. Do you have any ideas as to what might be causing the problem?
Thanks,
Daniel
Reply 8 years ago on Introduction
Hey, glad you built one!
Could be a bunch of things. Check the power gets to the arduino and it lights up, check the LED on pin 13 blinks every second. If these work try just one display, if that works try another power adapter. Check your wiring to the displays too.
Good luck!
11 years ago on Step 9
Hi,
First off thanks for the idea and the ible ;-)
I built one and I have a little question if you don't mind;
The clock works perfectly but it freezes up. If you do the IT repair (power off, power on) it works perfectly again.
Any ideas?
Oh, one more thing, for some reason the Uno is only pumping 3.4V DC from the 5V output, I found that I had to use the 5V supply to power the clock chip otherwise I got random code on the display and if your tried to change the clock time the number goes up and you can not select anything.
Put the 5V on and bob is your next door neighbour!
Thanks
Darren
Reply 11 years ago on Step 9
Hi Darren,
Someone else had the same with the time freezing, he fixed it by replacing the DS1307, but it could be the power if your board is only outputting 3.4v. You might also have a bad connection to the clock chip. The LED on the arduino pin 13 should flash every second to let you know the clock chip is being read and ticking.
Make sure you are not powering the Uno from the round power jack and check the voltage from the 5v pin without anything plugged into the Uno. If it still reads low, maybe there is something up with your Arduino or power supply. If not maybe you have a short somewhere. Good luck!
Nick
Reply 8 years ago on Step 9
Best bet is to run the 5V to the displays, and then run a 5V line to the 5V of the Arduino - so basically the Arduino is powered from the displays. That was how I fixed the problem.