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Change 7 seg disp. common cathode with common anode

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pasicr

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7segment common anode 4051

Hi,
I made this big digit hour clock 12/24, in this projects the big seven segment display 2,3'' is with common cathode.
I allredy have several 7 seg. display 2,3'' but with common anode.
I attached asm. file and schematic.
Please some body help me how can I use common anode vice common cathode in this projects.regards
 

uln2003 common cathode

I'd use inverters after the transistors (BC328) and after the multiplexer (IC4051)
 

7seg common anode transistor

Hi Mabauti,
please explain to me more detailed how can I do this,
regards
 

7seg common cathode transistor

1. Remove ULN2003 ..
2. Use inverters after 4051 ..
3. After inverters use PNP transistors connected between +5V and common anods (don't forget to filt 470Ω-1kΩ resistors between bases and inverters) ..
This should take care of the common anodes ..

As far as segment control is concern you can do the following mods:
1. Remove PNP transistors ..
2. Use inverters on RB0-RB7 outputs ..
3. After inverters use NPN transistors (you can leave the same resistors on NPNs bases and collectors, and connect NPNs' emitters to 0V) ..

Regards,
IanP
 

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    pasicr

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Hi IanP,
Help me about this
3. After inverters use PNP transistors connected between +5V and common anods (don't forget to filt 470Ω-1kΩ resistors between bases and inverters) ..
Did you meen base to inverters via resistor, emiter to +5V and collector to anods?
And second question:
3. After inverters use NPN transistors (you can leave the same resistors on NPNs bases and collectors, and connect NPNs' emitters to 0V) ..
base to invertor, emiter to 0V and collector to segment?
Can I use 74ls04 for invertors,
thanks
regards
 

3. After inverters use PNP transistors connected between +5V and common anods (don't forget to filt 470Ω-1kΩ resistors between bases and inverters) ..
Did you meen base to inverters via resistor, emiter to +5V and collector to anods?
Click to expand...
.. correct ..
3. After inverters use NPN transistors (you can leave the same resistors on NPNs bases and collectors, and connect NPNs' emitters to 0V) ..
base to invertor, emiter to 0V and collector to segment?
Click to expand...
.. yeah, inverter output --resistor--base ..emitter to 0V .. collector to anode ..

LS series may have to low VoutH to properly control PNP transistors, with NPN no problems, though ..
HC or HCT series will be better option, or if you have LS connect 4.7kΩ pullups between base of the PNP and +5V ..

Regards,
IanP
 

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    pasicr

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Thanks IanP for speedy ansfer,
tommorow I will make this change,
regards
 

Hi IanP,
You wrote:
...
3. After inverters use PNP transistors connected between +5V and common anods (don't forget to filt 470Ω-1kΩ resistors between bases and inverters) ..

I need one more info. The big 2.3'' display work on 12V. To drive anode for display I must put 12V on transistor.
Can I?

regards
 

Instead of 7404 inverters use Open-Collector inverters - 7406, for example ..
If you don't have them use first NPN transistor as inverter and then PNP to drine 7-segment of 12V rail .. see picture below ..

Regards,
IanP
 

why do not use uln2003 in data lines instead of select line and BC328 for select line rather than in data lines?
I think this is simple way for common anode.
 

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