7 segment and Microcontroller

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thanks so much for answer.
 

Hi.

I went to market to buy IC 4511 but i could not find it,could any one tell me how can i use IC 7447 with pic 16f877.(I am using multiplexing method)

thanks in advance
 

4511 is for common cathode display (active outputs are set to 1),
7447 is for common anode (active outputs are grounded).
What kind of display do you use?

Alex
 
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You can't use the 7447 but you can use 7448 which is for common cathode

Alex
 
thanks for reply, but they do not have latch enable, how can i use them in multiplexing mode?
as you said in previous post;we send data then enable the ic and so on ....
 

You have to use the classic multiplexing way as i have described in a previous post,
you also need 4 transistors, 1 to enable each display because only one of then will be on at any given moment.
You will use only one 7448 which will drive all abcdefg pins in parallel

set the value of the led 1 and enable led 1
wait 10ms (or lower) and turn off all leds (using transistors)
set the value of the led 2 and enable led 2
wait 10ms (or lower) and turn off all leds (using transistors)
set the value of the led 3 and enable led 3
wait 10ms (or lower) and turn off all leds (using transistors)
set the value of the led 4 and enable led 4
and then redo the steps.

Alex
 
but, how can i enable 7448,it has:LT, RBI, BI/RBO
which one shall i use?
 

sorry i did not understand what you mean by that image.
i was using the LE pin of 4511 before but now i dont know wich pin do i have to use with ic 7448
 

I was reading the datasheet,

LT should be H ,
BI/RBO should be high
RBI not connected

The above picture was to show the abcdefg connection

Don't connect all of them to the pic,
connect only the BI/RBO , when H the chip output will be on and will change according to the input (live not latched),
when L all outputs get low (off)

BI/RBO controls if the display is on or off
LT is lamp test , when low you will see the "8" light in the led
when H the output will change according to input, so connect it to H with a wire.

Alex
 
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so i use BI/RBO to make 7448 on or off like the LE in 4511.am i right?
 

No because when LE was H it kept the output to the last value, it didn't turn off the display ,
BI/RBO is like the BI pin in 4511, it activates/deactivates the chip (shuts down the outputs),
you can even leave it H all the time since the leds on/off state will be controlled with the transistors connected to the common cathode.

Alex
 
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I have attached the schematic,

use the transistor lines to turn everything off
send the data for the first led to the data lines
enable Q1
wait for a while but keep the data line as they were

use the transistor lines to turn everything off
send the data for the second led to the data lines
enable Q2
wait for a while but keep the data line as they were

use the transistor lines to turn everything off
send the data for the third led to the data lines
enable Q3
wait for a while but keep the data line as they were

use the transistor lines to turn everything off
send the data for the fourth led to the data lines
enable Q4
wait for a while but keep the data line as they were

Alex
 

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  • 7448.jpg
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one more question,is it possible to use one 7448 to drive four 7 segment?
BTW thanks for reply.

---------- Post added at 16:46 ---------- Previous post was at 16:41 ----------

Is this a good design?(with 4511)

 

You will use one 7448 as i did in the schematic and you will use the process i have described.
There is no need to use four 7448 since the outputs are not latched,
you were using four 4511 because each one could store a value and show it so no refreshing was needed until the value was changed,
this is not possible with four 7448, you would have to drive them constantly from 4x 4pins with the values for each led, there is no point in that.
It is better to use one 7448 and use constant refreshing of all digits, you will light them one after the other even if the value has not changed.

Alex

---------- Post added at 18:01 ---------- Previous post was at 17:57 ----------

No you can't use that schematic, because all the inputs are tied together and they will change together, these chip can't store the last data,
the output is a live translation of the input, the only way to use this schematic is if you separate the chip inputs and connect them to 16 separate pins.

use my schematic and connect all 8 leds in parallel and use 8 transistors to control the 8 displays (4 green, 4 red)

Alex

---------- Post added at 18:08 ---------- Previous post was at 18:01 ----------

Sorry, i thought you meant 7448...
Yes your schematic is correct for 4511.
 
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thanks so much for informative answer.
 

Hi,
There's no need to use so many drivers. Just use one and connect all the data lines (A-DP) together and to the driver output. Then send your data from the microcontroller and control the voltage going to the common pin as I had shown in one of your earlier threads.

Hope this helps.
Tahmid.
 

I think he wants to use the latched action of the 4511 to avoid the constant refreshing.
in this case he needs to use four 4511 as the schematic he has posted so that each chip can store a digit.
If not he can use 4511 exactly as 7448 in my schematic if he feeds the LE constantly with Low so that the output show the live result of the input pins.

Alex
 

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