LED Binary Clock

This is the second revision of my PIC based LED binary clock. The original version was the first PIC project I attempted, it used a PIC16F84A to do both the timekeeping and control the display matrix, unfortunately it didn't keep good enough time and gained about a minute every week.

This second version is based around a PIC16F628A running at 4MHz to control the display, it also uses a DS1307 realtime clock chip to do the timekeeping. Every second the DS1307 sends a pulse to the PIC chip, the PIC then reads the internal time from the DS1307 over the I2C bus and then displays the time in binary on the LED display.

The bottom row of LEDs display the seconds, the middle rows shows the minutes and the top row is for hours. The time displayed in the picture is 01100:010011:011011 or in decimal 12:19:27. The time is in 24 hour format so goes up to 10111:111011:111011 or 23:59:59

The PCB could be made double sided, or as I have done here single sided with 7 wire links soldered in place instead of the top copper layer. It has a 5 volt regulator so could be powered from any 9 - 15 volt DC power supply.

Step 1 Parts / Tools

As well as basic PCB making and soldering equipment you will need the following components:

1x PIC16F628A & programmer
1x DS1307 realtime clock chip
1x 32.768kHz watch crystal
3x BC548 (or similar) transistor
2x PTM pushbuttons
1x 78L05 regulator
2x 220uF electrolytic capacitors
17x Surface mount LEDs
1x DC power jack socket
5x 4.7K surface mount resistors
8x 100 ohm surface mount resistors
1x 2k surface mount resistor
12x zero ohm links (Or 11 zero ohm links and CR2016 backup battery)
1x 100nF surface mount capacitor
50cm single stranded bell wire
1x 9v - 15v DC power supply with DC jack

Comments

[botronics]

I would like to make this small enough to make a pocket watch out of it. To save power, is there a way to have the leds come on only when needed? Maybe this would work: If power to the pic only is left off, will the correct time show when the pic is turned on for a moment? While all the time the DS1703 is always running in the background to keep the time base.

[shuttleu93]

could you please draw up the schematic so it is easier to read please?

[ElevenOf9]

Hi,

The schematic files were available in the zip files, but I have also uploaded them now as images to the instuctable for easier viewing.

[dava_2]

.sch file isn't working with my software: ExpressSCH .

I what soft was made this .sch?

[ElevenOf9]

Hi, it was made in Eagle

[dava_2]

Thank you, works now!

[dava_2]

Anyone made PCB without those SMD components?

If you are interested, I can make it..

[pravardhan]

Nice Idea. But, why are you using PIC16F628A instead of PIC16F84a?

There is no schematic in jpeg format in the ZIP files and the one given in the site does not have the values of the components....!

And, is there any converter that can convert from Binary to Decimal? May be something like ADC (Analog to Digital Converter)???

[merseyless]

the fact that the time reads out in binary is the desired affect, if this is not to your tast then you could easily reprogram the chip to output the time to the serial port of a LCD display. but if you where capable of doing this then you would probably be content with learning how to read the time in binary form to confuse your friends. 2 + 2 = 10 in base four, I'm fine!

[sebborn]

hi how long did it take to build it

[ElevenOf9]

Hi, to actually assemble it only took a few hours.

[merseyless]

also, this project is pure genius!

[ElevenOf9]

Hi,

The PIC16F84A does not have an internal oscillator so would need extra components compared to the PIC16F628A to get it to work, the 16F628A is also cheaper than the 16F84A.

The compnents are listed in step 1 and steps 3, 4 & 5 show where they all go, but I'll try to get an updated schematic up in the next few days, I've only recently started using Eagle so I'm still finding my way around it.

You could impliment circuitry so convert the output from binary to decimal, but that kind of defeats the object I had in mind. An ADC would not help in this respect, you would need a binary to decimal decoder. It would be much easier to write an alternate program for the PIC to get it to output the time in the format you want instead though.

[sebborn]

hi

[moapz]

thanks eleven.
i create  it again, with new parts. the new one,work well.
thank you

[Muzamil Ali]

CAN YOU PLEASE SEND ME THE DETAILED NOTES OR CIRCUIT DIAGRAM OF THIS PROJECT...

[moapz]

hey. thank you for this.
it's finished, and work well :) but after 2day , it's off :( and i don't know why it is not work !
all LEDz is off!
i check voltages and it's good but i don't know why not work !
i changed all parts and create it again but not work !

[ElevenOf9]

Hmm, that's a tricky one, if it worked for 2 days then I don't see why it would suddenly  stop then. The first one I made I put the voltage regularor in backwards but that only worked for a few seconds before it burnt out. If you measure the voltage accross pins 5 & 14 on the PIC chip you should have 5 volts.

You asked in one of your other questions if you could use bell wire instead of the zero ohm links on the display PCB, if you did thta are you sure the wire isn't shorting out on the other tracks on the PCB? 

Try replacing the "1 second" LED (bottom right) to see if that makes any difference.

Try replacing the 3 transistors.

Th eone I made has been happily running for over a year now so I'm not sure what has gone wrong with yours, the only other thing I can think of is that there is a break in one of the tracks on the PCB, or a blob of solder is shorting something out.

[dimjan]

nice job
good !!!!!!

[moapz]

can I use bell wire instead of zero ohm ?
why zero ohm ?

[ElevenOf9]

Hi, yes you can use bell wire instead if you want, just make sure you don't short out the track that runs between the 2 contacts for each link. I used zero ohm links for 2 reasons, I think in this application they look neater than wire links and more importantly I have about 200 of them that I need to use up on something.

[lachlanmiller]

Could you clarify the concept of operation, i don't understand, how you are able to individually address each led from the pic, im assuming that you dont need to, and with this combination at any given time, you can turn on the required combination of led's to display the time.

could you explain this a little ?

[ElevenOf9]

Hi,

The LEDs are multiplexed, so at any given time only 1 row is illumiated, the PIC is constantly turning each row on and off so fast that it looks as though all 3 rows are illuminated at the same time. All 17 LEDs are controlled by 6 data lines and 3 address lines.

First of all the PIC loads the data for the seconds into PORTB, it then sets the address line for the seconds row high (turning on the LEDs) after a very brief pause it sets the address line for the seconds row low (turning off the LEDs). Then it loads the data for the minutes row into PORTB, turns on the minutes address line, paues, then turns it off again. The hours are displayed in the same way, then the whole process starts again.

A good visual example of how to multiplex LEDs can be found here:  http://www.franksworkshop.com.au/Electronics/RGB/RGB.htm

I hope this helps.

[frank the destroyer]

hey use the atmega128 you can make it do some pretty nifty tricks when tied to the rs232r serial converter chip ! 

[mr monoply33]

& bookmarked.

[Rob K]

Interesting.

You are setting the time to the clock chip  with buttons instead of already already having the time set with the pic to the chip through a ICSP. Good for resetting time when the clock is too fast or too slow, or changing  time zones.

As for the time being to fast that might be a watch crystal tolerances error.

[raykholo]

 This gives me an interesting idea:  if one were to mass produce these it might be better to add support for setting the time through another device and then connect it to this through a header/socket or maybe a set of pogo stick connectors so that the time can be set by touching a bundle of four, for example, onto printed contacts on the pcb itself.  
Bottom line:  make an easily settable time-keeping circuit, and then just touch it onto the corner of a remade pcb for this project to set it should a lot be made...

[ElevenOf9]

When you press either of the buttons it causes the time to change in the PIC's memory, and if you hold the button down the PIC will continue to change the time, as soon as you let go of the button the PIC writes this new time value back to the realtime clock chip and then continues on as normal. The dafault time value of 22:03:00 which is automatically set when the clock if first powered on is just an arbitry value I chose and can easily be changed with the buttons.

[drj113]

Excellent work.

I love the simple single sided look, as well as the extra display PCB. 

I have had a PIC binary clock illuminating my room for a year or so now.  It doesn't have a case either - There is something cool about the 'look inside' kind of project.

Regarding the inaccuracy of your previous version, I have spent lots of time mucking around with clocks, and the technique I use to deal with crystal tolerances, is to add or subtract a 0.1 second every 10 minutes, or hour, or whatever time is needed to improve the accuracy.  It takes a little while, and you need to keep accurate records, but in my case, the PIC 16F877 based Binary clock beside the bedside looses about a second every 2 months.

[ElevenOf9]

Thanks, I did try to do an automatic correction on it, but for some reason the rate at which it gained time was irregular so no matter what I tried I couldn't get it to keep good time. I seem to remember reading on one of the datasheets that running the 16F84A at 32kHz could cause the internal timer to behave unpredictably under certain circumstances but I have not been able to find that information again to confirm it.

By the way, I really like your word clock, I'm tempted to make one myself but I don't have room in my house for yet another home made clock.

[macobt]

Good binary clcok,here is mine with PIC16F84
my blog with few binary clocks
http://macoprojects.blogspot.com/

[drj113]

A technique I have used when there are no ICSP connections, is to use a short ICSP header cable, directly soldered onto the appropriate pins.  That has saved me *many* times :-)

[Kiteman]

Now you need some sort of case.

Actually (and this is a minor point, not meant to detract from a great project), if the LEDs faced "outwards" (away from the lower PCB), you could put it all in an opaque case, with holes drilled for the LEDs to shine through (although that's really just my personal aesthetic speaking there).

[ElevenOf9]

I did think about putting it in some sort of case, but I quite like the "bare bones" look it has, it makes it look a bit more geeky, but I suppose a binary clock is already quite geeky on it's own.