| ??? 04/22/05 17:26 Modified: 04/22/05 17:29 Read: times |
#92188 - optocouplers Responding to: ???'s previous message |
hi,
John D. Maniraj said:
http://www.freescale.com/files/mic...AN1775.pdf
I went briefly through this pdf and I had implemented a similar scheme with a pic microcontroller with 10bit ADC.I had buffered the resistor ladder network with a op-amp follower. Thanks, John. This is exactly the schematic I have used for natural buttons (with close resistence about 0 Ohm). But the problem is that here all buttons are isolated with optocouples which resistances (drop-out voltage of output photo-transistor) are not zero. This value inserts additional voltage between ground and R2R network and due it is not strong defined the results are very bad, trust me :( Regards, Oleg |
| Topic | Author | Date |
| ADC as digital input | 01/01/70 00:00 | |
| Saturation | 01/01/70 00:00 | |
| good point | 01/01/70 00:00 | |
| URL | 01/01/70 00:00 | |
| all good, but | 01/01/70 00:00 | |
| optocouplers | 01/01/70 00:00 | |
| Re: ADC as digital input | 01/01/70 00:00 | |
| go analog | 01/01/70 00:00 | |
| schematic | 01/01/70 00:00 | |
| It is possible to do but why..... | 01/01/70 00:00 | |
| opto | 01/01/70 00:00 | |
| Possible but troublesome... | 01/01/70 00:00 | |
| very informative | 01/01/70 00:00 | |
overcomming opto difference | 01/01/70 00:00 |