Dual Time Digital Clock Problem ? ( its about display )

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pasanrobotics

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Hey friends I made Dual Time Digital Alarm Clock.

**broken link removed**

I found it from hamradioindia And its working perfectly with small seven segments. But now I want to connect big jambo size segments.

( I tried some ics to do what i want. like 74HC541 and CMOS 4050. But its not working properly )

Can some one help me plz?
 
hi pasan,

You do not say how you have connected the 541, 4050 or jumbo LED's.

Post a revised drawing with your connections shown.

EricG
 
I don't really see what you're trying to do?, neither of the chips you mentioned have much output current capability (not really gaining much over the PIC). Either use ULN series drivers, or seperate NPN and PNP transistors - bear in mind you will probably have to invert the software as well.
 


can u give me some schematics for ULN
 
Try looking for the ULN2801A, that's an octal NPN driver - I believe they also do PNP ones, but they are not as common.
 
Just build a simple buffer like this for every segment of the display.
**broken link removed**
 
Why?

I see they're multiplexed but what stops you from using another buffer in series with each bank?
 
pasanrobotics said:
but cant ground emmiter.
Click to expand...

Of course you can, for the ones to ground - the top ones need to be PNP, with the emitter to +ve. Check my tutorial 'Hardware Extras' for examples of sinking and sourcing current.
 
Nigel Goodwin said:
Of course you can, for the ones to ground - the top ones need to be PNP, with the emitter to +ve. Check my tutorial 'Hardware Extras' for examples of sinking and sourcing current.
Click to expand...

Thanks again for ur help
 
Nigel Goodwin said:
Of course you can, for the ones to ground - the top ones need to be PNP, with the emitter to +ve. Check my tutorial 'Hardware Extras' for examples of sinking and sourcing current.
Click to expand...

Will they turn off with 7.5-12V on the emitter and 5V on the base? My analogue electronics is decidedly rusty.

Mike.
 
An NPN transistor turns on when the base is 0.6V about the emitter and a PNP transistor turns on when the base is 0.6V below the emitter.
 
Nigel Goodwin said:
Of course you can, for the ones to ground - the top ones need to be PNP, with the emitter to +ve. Check my tutorial 'Hardware Extras' for examples of sinking and sourcing current.
Click to expand...

Ya I checked ur Sinking' current from a lamp. But u cant aply it to this PIC CLOCK project. Coz Anode and Cathodes are driving from PIC. I am confused now
 
One side of the display connects to 0V (sink current - NPN), the other side connects to the +ve (source current - PNP), they don't need to switch both ways.
 
Nigel Goodwin said:
One side of the display connects to 0V (sink current - NPN), the other side connects to the +ve (source current - PNP), they don't need to switch both ways.
Click to expand...


Thanks bro. Now I get it.
 
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