[PIC] led message display with 16f84a?

[sukhoimg]

hello
i'am trying to build a panel that have the message HELLO with thèse dimensions 150*30 cm but i'am facing a problem .
the schematic below shows the leds of the letter H is there any mistake and would it work in realtiy and on a ditance of 50 cm from the control board?
View attachment e.bmp

 

[jayanth.devarayanadurga]

Let us assume each legs of the Letter 'H' takes 8 LEds and the dash between the lines take 6 LEDs. Make a series parallel combination such that each series combination takes 12V with or without series resistors. Connect the anodes to + 12V and the cathodes to ULN. If you have 3 series branch of LEDs for the Letter H then each branch current will be 20 ma. 60 mA will be the max current. Each channel of ULN can sink 500 mA. If all the 5 letters of HELLO take approx 60 mA * 5 = 300 mA then all cathodes can be connected to one o/p of ULN. better use NPN TIPxx transistor which can handle 1A.

 

[sukhoimg]

Let us assume each lega of the Letter 'H' takes 8 LEds and the dash between the lines take 6 LEDs. Make a series parallel combination such that each series combination takes 12V with or without series resistors. Connect the anodes to + 12V and the cathodes to ULN. If you have 3 series branch of LEDs for the Letter H then each branch current will be 20 ma. 60 mA will be the max current. Each channel of ULN can sink 500 mA. If all the 5 letters of HELLO take approx 60 mA * 5 = 300 mA then all cathodes can be connected to one o/p of ULN. better use NPN TIPxx transistor which can handle 1A.

but i want to use an 9 v power supply ?

 

[jayanth.devarayanadurga]

The series combination should have 3 LEDs. (2V per LED)

 

[sukhoimg]

so i'am right?

 

[jayanth.devarayanadurga]

Yes. But still needs a series resistor for each series path.