led display (on behalf of Davedpg)

[Harald Kapp]

Hi all, newbe here. Need help re: 7 segment numerical display.
What I have is a bcd output @5v. I have the truth table and can do only so much. ATM from my output device I have 9 buttons to select obviously 1 tru 9. Right now it will display 1 tru 9 on a 7 segment display and also 9 LEDs 1-9 with a CD24hc4511 logic. Happy days! What I really need is 3 x 7 segs to display instead of number 1 I need 160. number 2 to read 80 3-40, 4-30 5-20, 6-17, 7-15 8-12 and number 9 to read 10.
endless googling steers me away from bcd. It has to be driven from bcd.
Help please

 

[Harald Kapp]

Today the easiest way is a microcontroller programmed to display just what you want in response to the button pressed.
Another, comparatively simple way is using a look-up table. Use the BCD code from your input (0...9) as the address into a ROM. Program the ROM to output the 7-segment code for your display. A standard ROM typically has 8 data bits, therefore 3 ROMs would be required in this most primitive setup.
However, you can use multiplexing to reduce the number of ROMs to 1: build a counter to 3 (0, 1, 2), use the output from the counter as upper 2 address bits to the ROM and to select the corresponding digit from teh 3 digit display. See e.g. here for more information on multiplexing 7 segment displays.

 

[Davedpg]

Thanks Harold. You confirmed what I suspected to be the answer. However, programming a ROM is new to me. I am wiling to learn but need pointing toward what I need to achieve this i.e. a usb programmer, which ROM chip, bcd decoder etc.

 

[dorke]

Is this home work?