thebouljello
- Aug 16, 2016
- 8
- Joined
- Aug 16, 2016
- Messages
- 8
The open-collector outputs serve to ground the cathode segments of the common-anode 7-segment display, thereby illuminating that particular segment. The resistor pack serves to limit the LED current when the 74LS47 output goes low. A pull-up resistor connected to the 74LS47 output does nothing except increase the current an output would sink when the output is low, being essentially in parallel with the LED/current-limiting resistor associated with each segment.The 74ls47 has open collector outputs.
Try connecting a 2k pull up resistor from +5 to each output pin of the 74LS47.
The open-collector outputs serve to ground the cathode segments of the common-anode 7-segment display, thereby illuminating that particular segment. The resistor pack serves to limit the LED current when the 74LS47 output goes low. A pull-up resistor connected to the 74LS47 output does nothing except increase the current an output would sink when the output is low, being essentially in parallel with the LED/current-limiting resistor associated with each segment.