seven segment with LEDs

[dev_shr]

hello guys, i wanna make seven segment display using LEDs and interface it with 8051 to make a countdown. i have thought to make a single segment with 4 leds so that there will be 28 LEDs in one seven segment. plz help me with how to connect these LEDs so that they would glow enough.further i am thinking to combine more seven segments to make digital clock.

 

[hh123]

yes can do it..just see the driving of LED's to make them glow brighter and glow with equal brightness

 

[mishra12]

hi dev shr so finally you want to make digital clock large using four leds in each segment here is the solution **broken link removed**
five leds are connected in the circuit but you can reduce to four leds with suitable resister

 

[Embedded Partner]

make 7 segments of 4 led's EACH
P0.0 - LD1
P0.1 - LD2
....
P0.8 - LD8
and so on
i f you wann to glow '1'
set LD6,LD8,LD10,LD12,LD18,LD20,LD22,LD24

LIKE THIS YOU DISPLAY ANY NO
I HOPR IT MAY HELP YOU



.. ....... LD1 LD2 LD3 LD4...........
LD5....................................... LD6
LD7...................................... LD8
LD9....................................... LD10
LD11..................................... LD12
........ LD13 D14 LD15 LD16................
LD17 ..................................... LD18
LD19...................................... LD20
LD21 .....................................LD22
LD23 ......................................LD24
..........LD25 LD26 LD27 LD28............

 

[dev_shr]

hi dev shr so finally you want to make digital clock large using four leds in each segment here is the solution **broken link removed**
five leds are connected in the circuit but you can reduce to four leds with suitable resister

sorry for late reply but i was trying to do as you said but it didn't work. i haven't used shift register and i am using uln2003A. Inputs to uln2003A is fed from microcontroller's port 2 and each output of uln2003A is fed to cathode of each segment of display. i have used resistor of 220 ohm in each segment and supply of 12V dc. i have used the following mapping:

0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F

the problem is that display is very dim. i even have ground pin 8 of uln2003A and when i ground pin 9 every segment glows very bright. i don't know what is wrong with this. I even tried with the pull up resistors in the input of uln2003A but it doesn't work either. please help me with some solution.

 

[mishra12]

can you upload your circuit so that we can trace
try to make common anode seven segment only first
in this circuit i tried to connect resistor suitable to anode led in series and cathod to uln2003 out put .
why you use 220 ohm resistor i don't know ?
since four leds are in series resistor value will decrease (12v)

 

[dev_shr]

i have attached the circuit diagram. i have used 100 ohm resistor to achieve 40 mA current from +12 V supply.

 

[mishra12]

yes your circuit is correct each led is 3v rated so no need to use 100 ohm that will dim your display