Timeline for Pull-up resistor - why input pin is pulled to ground when the switch is closed?
Current License: CC BY-SA 3.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Nov 12, 2017 at 0:07 | vote | accept | user1764381 | ||
| Nov 11, 2017 at 16:44 | history | edited | Trevor_G | CC BY-SA 3.0 |
added 61 characters in body
|
| Nov 11, 2017 at 16:38 | history | edited | Trevor_G | CC BY-SA 3.0 |
added 61 characters in body
|
| Nov 11, 2017 at 16:32 | history | edited | Trevor_G | CC BY-SA 3.0 |
added 61 characters in body
|
| Nov 11, 2017 at 16:31 | comment | added | Trevor_G | @SamGibson Thanks, you are of course correct, I must admit I only glanced at the OP's image. Fixed :) | |
| Nov 11, 2017 at 16:30 | comment | added | SamGibson♦ | @Trevor - Hi, regarding "For a TTL device, as you have shown, the zero logic level current coming out of the pin is MUCH larger than the high level current that enters the pin." - But the OP has shown a 74HC04, so not TTL (that's CMOS fab, with CMOS logic thresholds, in a TTL-compatible pinout) and it doesn't have the TTL input current behaviour that you mention. Therefore perhaps better not to get into the TTL behaviour except as a side-note? Or did I miss something? | |
| Nov 11, 2017 at 16:25 | history | edited | Trevor_G | CC BY-SA 3.0 |
added 532 characters in body
|
| Nov 11, 2017 at 16:16 | comment | added | Trevor_G | @user1764381 that is correct. When the switch is closed you effectively have two circuits. One is the resistor. | |
| Nov 11, 2017 at 16:14 | comment | added | user1764381 |
Thanks @Trevor. obviously current is flowing through the resistor to ground, do you mean that when the switch is closed, no current is flowing through R1 to the input pin?
|
|
| Nov 11, 2017 at 16:02 | history | answered | Trevor_G | CC BY-SA 3.0 |