is it right ?!

HI All ,

it's my first time to use the BCD driver 74LS47 , I have 4 pins that i don't know where to connect , or it's not necessery to do that espacilly that i'm sending from PIC16f84

the pins are : 3,4,5,6

and here is the schemaic i drawn you can view it

please tell me if this is not right because i'm going to print this PCB

thank you

sorry i forgot to upload the photo ,here it is .

I can't remember old TTL. I lost my TTL Cookbook about 30 years ago when I discovered Cmos.

I think the RB3 output of the PIC is driving the dead short of the transistor's base-emitter junction. The PIC might fail or become overheated. It should have a current-limiting resistor to limit the current to 25mA or less.

Hi Watzmann,

Pin 3 is Lamp test and should be connected to +5v.
Pin 4 is BI/RBO Should be left open.
Pin 5 RBI connect to +5v.
Pin 6 is the D input.

on1aag.

yes what i need , thanks too much ,

audioguru about your transsitor comment i'll use 470 ohm resisor between the base of the transistor and the RB3.....is it safe ?

watzmann said:

yes what i need , thanks too much ,

audioguru about your transsitor comment i'll use 470 ohm resisor between the base of the transistor and the RB3.....is it safe ?

Click to expand...

When the PIC output tries to go to 5V then the 470 ohm resistor will limit the current to about 8mA because the output high voltage from the PIC will be loaded down to about 4.5V. 8mA is fine.

i tried to connect some LEDs to the output of the 74ls47 and the other side i mean pin 7,1,2,6 to PIc16f877 , i mean that i need to let my pic run the 74l47 and that lead the LEDs to light .

i followed the datasheet truth table , but no led work ....

if you opened the attached photo , you'll find that all the outputs of the 74ls47 is High although i'm sending high on one terminal RB.5 from the pic , how to turn them low to run my LED

all of that work i'm still simulating at Proteus

please view the photo and tell me what's wrong.