Big 7 seg LED display

[shahidali55]

If the UDN2981 is available here, that'll be my first choice...
Thanks Dave for the nice chip find and Sayzer for the schematic...

[shahidali55]

I found another cheap alternative...
<img src="http://www.winpicprog.co.uk/graphics/lamp_source2.gif" border="0" alt="" /></div>

[shahidali55]

..........

[sayzer]

I believe UDN2981 would be cheaper since you would have to use many transistors.


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[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.


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[Dave]

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

[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.