AT89s52 and 7 segment

[Medtronic]

at89s52 port current

Hi all
can i connect an AT89s52 direct to 4 seven segment Display without multiplexing
"i mean every port to 7 seg"
Thanks alot

 

[IanP]

7 segment fnd

Of course you can but remember that:

Under steady state (non-transient) conditions, IOL must be externally limited as follows:
Maximum IOL per port pin: 10 mA
Maximum IOL per 8-bit port:
Port 0: 26 mA Ports 1, 2, 3: 15 mA
Maximum total IOL for all output pins: 71 mA
If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater
than the listed test conditions.

what means, that you will have to use driver(s) or anythink that can sink (7-segment with common anode) or source (7-segment with common cathode) more current ..

Regards,
IanP

 

[Medtronic]

how to glow leds by using microcontroller at89s52

Thanks Ianp too much
but can you explain the board at mcselec/kits/SE-CLOCK-FND
please look at thise board and try to explain it
thank too much again

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[brevor]

at89s52 dengan seven segmen

Most likely what is being done is the segments within each 7 Seg display are individually multiplexed. This way only 1 segment is on at any time and the average IOL is only 10 Ma.

https://www.mcselec.com/index.php?o...s&flypage=shop.flypage&product_id=97&Itemid=1

 

[IanP]

port 0 sink current at89s52

They assumed that not all segment would be on at one time (can you imagine situation like 88:88 - of course not), so the combined segments' current could be moretheless within 89C51 max Iol total ..
Also, by using 470Ω curent limiting resistors max current per segment is only ≈5mA ..
But don't expect the segments to shine to brightly ..

Regards,
IanP

 

[~E3016~]

at89s52 port drive current

Hi all
can i connect an AT89s52 direct to 4 seven segment Display without multiplexing
"i mean every port to 7 seg"
Thanks alot

Why you want to direct all port to the all seven segment? i think the multiplexing methode is better...

Besides the consumptions current is lower, the port is less...

 

[IanP]

multiplexar de display con el at89c52

.. Ithink the multiplexing methode is better...

Besides the consumptions current is lower, the port is less...

I have to disagree with this satements ..
First of all, even if the multiplexing method uses less control lines, but, if you have planty of them available - what's the point???

As far as power consumption is concerned, one has to deliver, on average, certain amount of current to ensure certain level of LED brightness ..
Tell me, what is the difference between, for instance, 5mA DC and 50mA @ 10% PWM?
After all, these 89C51 pins are unable to deliver more than x mA of Iol current ..

Regards,
IanP

 

[Medtronic]

common cathode

Thanks Ianp for replay
but do you think there is no difrence between 5mA and - 50mA for short time with
a verage caculated to be 5mA - at the brightness of leds
Thanks again for all replay
wating for answer
MedTronic

 

[IanP]

uln2003 7seg

5mA - yes - but to sink 50mA (or more) you need something capable of doing so ..
8051 pins CAN NOT do that ..

Regards,
IanP

 

[Medtronic]

at89s52 port

Thanks Ianp for fast replay
you are so helpful , i understand what you mean
another small question
you know the led can't pass more than 25mA,how can i make the led good bright
with multiplexing,how to caculate that
for example if i have 8 leds,i want to scan it what is the curent to thise leds to be
go brightness
thanks again

 

[~E3016~]

seven segmen dua port at89s52

Thanks Ianp for fast replay
you are so helpful , i understand what you mean
another small question
you know the led can't pass more than 25mA,how can i make the led good bright
with multiplexing,how to caculate that
for example if i have 8 leds,i want to scan it what is the curent to thise leds to be
go brightness
thanks again

You can use the current driver, like ULN2803 and UDN2981, here is the datasheet

 

[rashslash]

at89s52 7 segment 4 display

well simply connect uln2003 500ma driver to the micro and then to the 7 segment

 

[Medtronic]

seven segment fnd

thanks for all
but lets talk about brightness of scaned leds how can i caculate the current for good bright with scan
thanks again

 

[IanP]

7-segment with at89s52

You will need data sheets of your LEDs ..
There you will find out what current should be used to obtain a suitable brightness ..
Lets say, you need 10mA per LED ..
As the LEDs are multiplexed you need at least a current of about 80mA / LED @ 12.5% duty cycle (for 8 LEDs), so the average current is: 12.5% *80mA = 10mA ..

Regards,
IanP

 

[sn_burki]

7-segment with at89c52

hi

in multiplexing,,, how much current is required??? how to know this? I want to glow LEDs in multiplex status with ful bright. what is the formula?

 

[Medtronic]

7-segment display using at89c52

Thanks Ianp for replay...but this time you are too late, i wait you too much but
you are so helpful again, i understand what you mean ,cause it what i predect
thanks too much