Big 7 seg LED display

[shahidali55]

Hi everyone, thanks for all your help.
I made my LED clock using transistors cause i couldn't get the UDN2981.
It works great. I added an hourly animation and a battery battery backup also ( i cant belive i'm getting more than 20 hours out of a 60mAh rechargeble battery {with display off}).
I've attached a picture of it...

[sayzer]

Good to see something is working!

FYI: Upon the chip info above, I checked the prices.
The price of UDN2981 is around US$1.60-1.70 (for 1000s lots), which is a lot more expensive then traditional ULN2003 types.


------------------

[Dave]

sayzer, It probably is but I don't think you can source current with a ULN2003.

[sayzer]

Yes, of course Dave.

I had no info about this UDN2981 before, but now I will consider it when the project allows me to use it (cost & hardware etc.).


Thanks for the info.


-------------------

[Zhao Hui]

Hi everyone, thanks for all your help.
I made my LED clock using transistors cause i couldn't get the UDN2981.
It works great. I added an hourly animation and a battery battery backup also ( i cant belive i'm getting more than 20 hours out of a 60mAh rechargeble battery {with display off}).
I've attached a picture of it...

shahidali55,
May I get your schem about the final Common Anoda display 7 segment (12 V) to me, couse i've same problem with you before.
thanks for helping ...

[email protected]

[shahidali55]

Hi Zhao Hui.
Check post #20.
That schematic will drive the high current consumption at the common anode pin.
The individual cathodes can be driven by a single NPN trasistor buffer each.
Check the schematic below (for seperate cathode drive).
This circuit will invert the PIC inputs so dont forget to correct this in software.

[shahidali55]

Zhao Hui and mdaweb, here is the schematic.
The display should be a common anode display.
The 9.6v input shown in the schematic should not exceed the display max segment voltage.
I have shown the connection only for the 'a' segment. The patern just has to be repeated for the rest of the segments.

I have been using this circuit for some time now. It works great.

But the operating logic is a bit different.
Logic 1 on both p.1 and p.2 will turn segment 'a' on.
p.1=1 and p.2=1 --> seg'a' on
p.1=1 and p.2=0 --> seg'a' off

[Zhao Hui]

shahidali55 and all you guys in this forum......... thank's alot for technical information my job almost done now...
once again thaaaaankkkkkkkkk's

pic 16F628 with 4digits (10 inc) 7seg 12 Volt



zhao hui

[Zhao Hui]

Here the final Schem that work fine, no software modification on PIC ..... just use the CMOS Inverter (4049 - Hex Inverter) to invert the logic.

[shahidali55]

I'm having certain 'strange' errors in my digital clock.
Processor = 16F84A @ 4 Mhz
4 inch , 12 volt LED Display
The schematic is almost the same as the one in the previous post.
(A battery backup has been added)

Problem 1:-
The clock sometimes just 'hangs'. I think the oscillator stops or something.
The display goes blank or most of the time only one digit on . . .

Problem 2:-
Timer0 is used for timekeeping (Darrel Taylor's Instant Interrupts).
The clock suddenly stops incrementing time.
i.e. the display multiplex routine keeps working as it can be seen that the all the digits on the display are displaying time.
The thing is that the time never increments.
I have programmed the colon between the digits to blink at 0.5 Hz.
This blinking is controller by the time keeping registers mid byte which is kept updated by timer0.
Since the digits keep showing a frozen time, and the colon stops blinking,
Could it be that timer0 has somehow accidentally been disabled ? ? ?


Attached Files :-

clock.pbp - main file
TMR0_int(ASM).pbp - interrupt handler

Could someone please help me out ?