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89C51 Based LED Calculator Project

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Hi Everyone
I have to do with a LED calculator project. Its working, But the brightnes of the LED segment is too low. How to amplify it?

This is the circuit diagram. I use TIP 127 in port 2. But all display segment are active.

Any suggession please....

Reguards Manoj Soorya
 

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ronsimpson

Well-Known Member
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This is the circuit diagram. I use TIP 127 in port 2. But all display segment are active.
I see no TIP127 in the diagram.
Its working, But the brightness of the LED segment is too low.
The brightness is low (with or with out) the TIP127???
The resistor pack: is it pull up or pull down? What value?
To turn on a LED what do you do?
>Is "A" high and "1" low? OR Is "1" high and "A" low?
>What voltage to turn on the LED? 1.8 volts?

upload_2016-9-2_18-3-42.png
 
Thank You for your attension In my Post.

There are no TIP127 or 125 in the circuit. I just implemented.

The Brightnes is low without TIP127. I use Common Anode Display. I just connect the TIP Darlington in Port 2.

The Resistor pack pull up with 10K resistors.

I can make a video and upload shortly...


Thank you again for your attension In my Post.
 

ronsimpson

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The 8051 Port0 only pulls down. The resistor pack is the only pull up on port0.
The other ports pull up but not well. In this diagram I show a internal 500 ohms to show how bad the old 8051 pulls up.
Here I added a 2N2907 to amplify the pull up current of Port2. (this inverts the output so in software you will need to invert the data sent to port2!!!!!
R12 10k limits the base current for Q2. (about 0.4mA) (maybe 3.3k is better)
With the 2N2907 or MPS2907 will pull up hard.
You might need R14, 100 ohms to limit the current for the LED. (resistors on each segment and DP)
upload_2016-9-2_20-16-42.png
Do not use the TIP127.
 
Hi ronsimpson,

I think I leave from this project. Its have lot of drawbacks. It does not have the decimal point. If it have, its good for me. Thats why I think leave from this project. Can you any Idea to make another one or any link? I have the keil code for this project. Please have a look for it

Anyway, Thank you for attension and replays about my project. Have a nice time.

Reguards
 

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atferrari

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Wow! A quick retreat. At least, most if not all soldiers ready for the next battle...
 

Ian Rogers

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Calculators are easy.... There are enough people here to help.... I would drive the LED screen via shift resisters and simple npn's to get the brightness... The problem is just usually the time to update... When I use several LED modules, I almost always use an interrupt to drive the LED display so I keep the duty cycle constant!!

If the duty cycle is too low then you won't see anything... As for the floating point.. Most compilers have ftoa() for such purposes...
 
Thanks all for your valuable help. Thanks again. I need really a circuit diagram for another Calculator circuit. If anybody have?
 
Calculators are easy.... There are enough people here to help.... I would drive the LED screen via shift resisters and simple npn's to get the brightness... The problem is just usually the time to update... When I use several LED modules, I almost always use an interrupt to drive the LED display so I keep the duty cycle constant!!

If the duty cycle is too low then you won't see anything... As for the floating point.. Most compilers have ftoa() for such purposes...
In this calculator program, which line can I change for the duty cycle?
 

Ian Rogers

User Extraordinaire
Forum Supporter
Most Helpful Member
First... You need to ask yourself what functions your calculator will have???

+, - , /, * are the simplest... If you want trig and square.. This can be done with tables..

Your schematic just needs drivers for the display, then sped up...

8 multiplexed digits need more current as the time share is small, however! The duty 8:1 is really good if the current were there..
 
First... You need to ask yourself what functions your calculator will have???

+, - , /, * are the simplest... If you want trig and square.. This can be done with tables..

Your schematic just needs drivers for the display, then sped up...

8 multiplexed digits need more current as the time share is small, however! The duty 8:1 is really good if the current were there..

Thanks again for your Ideas... But I got a nice calculator from a Russion site.. I think its suite for me.

This is the link , Please check : http://elektro-shemi.ru/kalkuljator_na_svetodiodnykh_indikatorakh.html


Thank you all for your Help
 
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