| ??? 01/21/05 08:37 Read: times |
#85467 - Inputs |
Hi all, I have a problem with the inputs to my controller. I am using an 89S51. I set the input pins high to enable them, the problem is that the change in state is not "seen" by the micro.
An opto-coupler is providing the input, with the collecter tied High "1" and the emitter connected to the pin. I thought that when the opto is off the input will float so I used a pull down resistor. The result is whan a 10K was used -> High = 4.97V , Low = 3.55V When a 1K resistor was used -> High = 1.61V , Low = 0.00V Can anyone help, I am at a loss! Thank you for your time. Sun |
| Topic | Author | Date |
| Inputs | 01/01/70 00:00 | |
| Opto | 01/01/70 00:00 | |
| Opto input | 01/01/70 00:00 | |
| Optocoupler Designer’s Guide | 01/01/70 00:00 | |
| What type of opto? | 01/01/70 00:00 | |
| pulling high | 01/01/70 00:00 | |
| Why??? | 01/01/70 00:00 | |
| Misleading.... | 01/01/70 00:00 | |
| OK, clearer | 01/01/70 00:00 | |
| I must be stupid... | 01/01/70 00:00 | |
| you are not | 01/01/70 00:00 | |
| Heres Why | 01/01/70 00:00 | |
| Not quite so. | 01/01/70 00:00 | |
| Pull-downs must be much smaller! | 01/01/70 00:00 | |
| OK you are right. | 01/01/70 00:00 | |
A little history | 01/01/70 00:00 | |
| Link... | 01/01/70 00:00 | |
| use opto-coupler as NPN | 01/01/70 00:00 | |
| Thank you All, & a question for Kai | 01/01/70 00:00 | |
| Opto to pull-down signal | 01/01/70 00:00 |