| ??? 05/23/05 17:29 Read: times |
#93779 - I know they're quite old... Responding to: ???'s previous message |
...but I could get quite a few of them for free and it would be a shame not to use them for the purpose I have in mind.
I want to use them to separate the IO-pins of a PCF8574 on my PCB from the 'outside world', to protect the 'sensitive' electronics. I've drawn already something myself. It's a principle schematic to detect when a button is pressed, but I'm not sure if the dimensioning of the components is correct: 
I've used the following 'way of reasoning' to determine the components: - Diode: If=10mA / Vf=1,2V => R = ( 5V - 1.2V ) / 10mA = ~ 390ohm. - Transistor: Vcesat = 0.2V / Ic=5mA => R = (5V - 0.2V ) / 5mA = ~ 1kohm. I also want to use it the other way around: controlling the diode with the IO pins and for instance controlling a LED/relay/... on the transistor side. Best rgds, --Geert |
| Topic | Author | Date |
| CNX83: application examples? | 01/01/70 00:00 | |
| HOW | 01/01/70 00:00 | |
| did you find some in a drawer | 01/01/70 00:00 | |
| I know they're quite old... | 01/01/70 00:00 | |
| Better | 01/01/70 00:00 | |
| Schmitt Trigger | 01/01/70 00:00 | |
| nothing wrong - but | 01/01/70 00:00 | |
| Not working, Erik | 01/01/70 00:00 | |
| Pullup Or Not | 01/01/70 00:00 | |
| Additional Comment on Rise Time | 01/01/70 00:00 | |
| Confustion maybe? | 01/01/70 00:00 | |
| Yes, you need on PCF8574 | 01/01/70 00:00 | |
| No hijacking at all!!! ;-) | 01/01/70 00:00 | |
| Walks like a duck? Quacks like a duck? | 01/01/70 00:00 | |
| Yes, I do have quite a few ducks... | 01/01/70 00:00 | |
| Correct? | 01/01/70 00:00 | |
| Correct !! | 01/01/70 00:00 | |
| you must have edited | 01/01/70 00:00 | |
| I didn't do anything... | 01/01/70 00:00 | |
I do not know | 01/01/70 00:00 |