Hello again.
First I need to explain my circuit.
The problem I am showing you is part of a bigger circuit, which will eventually be a dual egg timer. Attached is a circuit showing one quadruple 7 segment display, which eventually will be doubled.
My microcontroller is pulsing the clock input on a 4017 decade counter, each output from 0-3 is connected to common anode of each of the 4 digits on the display. Since all digits share catodes a-g + punctuation mark the circuit needs to be multiplex. Each time the 4017 is clocked, the microcontroller outputs a different BCD code fed through a SN74LS47 BCD to 7 segment decoder, then further to a-g inputs on quadruple 7 segment display. I have this circuit right, see video, problem comes next.
http://www.youtube.com/watch?v=Z0-M1H9PTqs
These logic devices provides next to no current to my LEDs, as shown by the dim/non-bright digits on the video. I need to amplify this, but do I need both PNP on LS47 side AND NPN on 4017 side? As the LS47 can hardly sink anything, and the 4017 can hardly source anything.
As always, I am thankful for any advise here
EDIT 1: Also, one more think I want to know. Since I will double the amount of displays, I will face the problem of one segment being lit either none, one or two at the same time. In the case of one of the displays lighting say "g" segment, I must limit the current the half of what is needed for when same segment "g" is lit on both displays. Is there a workaround for this? Do I just add two separate but identical current limiting resistors in parallel from transistor on whatever side it is placed?
First I need to explain my circuit.
The problem I am showing you is part of a bigger circuit, which will eventually be a dual egg timer. Attached is a circuit showing one quadruple 7 segment display, which eventually will be doubled.
My microcontroller is pulsing the clock input on a 4017 decade counter, each output from 0-3 is connected to common anode of each of the 4 digits on the display. Since all digits share catodes a-g + punctuation mark the circuit needs to be multiplex. Each time the 4017 is clocked, the microcontroller outputs a different BCD code fed through a SN74LS47 BCD to 7 segment decoder, then further to a-g inputs on quadruple 7 segment display. I have this circuit right, see video, problem comes next.
http://www.youtube.com/watch?v=Z0-M1H9PTqs
These logic devices provides next to no current to my LEDs, as shown by the dim/non-bright digits on the video. I need to amplify this, but do I need both PNP on LS47 side AND NPN on 4017 side? As the LS47 can hardly sink anything, and the 4017 can hardly source anything.
As always, I am thankful for any advise here
EDIT 1: Also, one more think I want to know. Since I will double the amount of displays, I will face the problem of one segment being lit either none, one or two at the same time. In the case of one of the displays lighting say "g" segment, I must limit the current the half of what is needed for when same segment "g" is lit on both displays. Is there a workaround for this? Do I just add two separate but identical current limiting resistors in parallel from transistor on whatever side it is placed?
Attachments
-
190.8 KB Views: 52
Last edited: