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Topic: Bring New Life to Elektor Jumbo clock (Read 379 times) previous topic - next topic


Hi everyone ,

this will be my first project after i played around with the Arduinos examples  and wonderful  projects like the Parola_Lib .

My project is to use a 10'' Jumbo 7-segment Led displays i Build almost 30 years ago based on the Elektor Magazine issue of Jun, 1985, its called  the Jumbo Clock.

about the old one :
i don't have the controller board any more but i remember it was using 2 x 7216 Eproms , they were burnt with a code that handle the  7-segment displays work and the flashing colon in the middle and the Temperature negative sign and the degree symbol ,was based on the 50Hz time base from the AC line,  some logic math chips , an ADCxxx Analogue/ digital converter chip ,an LM335 Temp sensor and 2 switches to adjust the Time ( Fast ,Slow).

the 7-segment Jumbo displays each use a 74LS248  BCD to 7-segment decoder with a MPSA14 transistors on the output ,current limiting resistors  and run on 24V dc.

MY Project :
to use the Arduino ONO or 2560 to drive the Jumbo displays  , keeping the same clock / Temperature Functions , but using new approach to the design .

I'm planing to use the DS1307 time base for clock time keeping  and use either the DHT11 or LM35 /LM335 for temperature sense (depending on the code complexity), i'm a C++ novice i only did  basic and PIC Assembly in the past.

the  74LS248 takes  BCD code and decoded to 7-segments so properly have just to read time from the DS1307 and pass it through to the right digit.

my Questions  ,   i have 2 ideas  , either go with a direct drive (4-bit per display) and the LT,RBI,Upper Degree Symbol, Negative sign  =20 pins + 3 for sensors and 2 for switches (witch i can omit for now because i can set DS1307 and forget about it).

Or Remove the 74LS248 from the displays and use a MAX7219 and Multiplexing  the displays.

OR i'm open for any idea will make the project easier , i'm going to be relying on the code blocks from the Arduino libraryes
because of me not knowing C++  i have no problem with Hardware.

please check my attachments  i appreciate any help.
We are Limited by the Technology of our Time .


Arduino + 4 TPIC6B595, very easy to do.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


Thanks for replying ,
I'm assuming the TPIC6B595 are a high current chips comparing  to the 74Hc595 (which i have a handful of them in my lab),
i probably can use the 74Hc version and feed the output to the already mounted  NPN darlington  transistors on the displays.

I can go this way !

Is there a code for a project that use the 595 in a Time /Temperature clock like the  design i'm looking for. as i mentioned before  C++ is my limitation. and i don't want to invent the wheel again.

We are Limited by the Technology of our Time .


Yes 74HC595 and NPN transistors will drive the LED strips.
I am sure there is existing code to run a clock and read/display a thermal element,
Try looking in the arduino playground
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


Jul 28, 2014, 04:46 pm Last Edit: Jul 28, 2014, 05:02 pm by PaulRB Reason: 1
Hi, you could use a ds3231 rtc instead of ds1307. They don't seem to cost more if you shop around, are more accurate, use almost identical code, same i2c bus connections and have a built-in temperature sensor.


Also don't worry about having no experience in C/C++. If you can program in any language, you can program in any language! Just have to get used to it. Plenty of help available on this forum.



Thanks for the help , i'm going to order a couple of the DS3231  and see how it works ,

As far as the progress of my project , i already have one display modified and running with the 74HC595  instead of the 74LS248 , it wasn't so bad  , i used the same Dip socket and did some wiring on the back for the segments and power .

i'm running the clock now with a NANO Mini and a DS1307  with one display , i'm waiting on some more of the 74hc595 to come in the mail because it turned out that only  have 2 IC's in  DIP package and a bunch in SMD and i didn't want to miss up the pcb so i'm going to wait for the others.

As far as the code, i found  a code  to do exactly what i need  , i'm just going to do some preference modification to it , like the timing  for the Temperature display , how long to be on and how  many seconds to be on (i think the original  was 3 seconds).

also i want to change the format form 24H to 12H and figure out how to blank the 10's Hour digit when its 9H or less.
It shouldn't be bad just some light tweaking.

i will post the whole project with code and documents after i get it done for any one likes to construct the Jumbo Clock.
We are Limited by the Technology of our Time .

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