| ??? 05/25/07 23:23 Read: times |
#139852 - an exercise for the student Responding to: ???'s previous message |
Sulaiman Saeed said: It seems to me that you're then left with the option of postulating your frequency. If I were doing that, I'd postulate 500 Hz, which is slow enough that you can keep up and fast enough that you can easily AC-couple it through a series capacitor. Consider, then, what would happen when you apply a bias voltage to the output of the capacitor, equal to, in this case, Vcc/2. It's likely that you'd be able to measure the voltage with your ADC, wouldn't you? The capacitor removes the DC component from the input signal. Now, rather than being a sine of 4 volts peak-to-peak centered about GND, it will be that same sine of 4 volts peak to peak, centered about Vcc/2. That should make a measurement possible. Hii
Mr. Richard you are right, the 0=GND and 5V=Vcc. Before explaining the question furthermore I just wan to share a small problem of mine. My professors are all Arabs and most of them usually fail to entertain us with their teaching and although being a bright student I and also my colleagues still can't understand the most simplest of things because of their language problem. What I understand is that my professor wants to know that when I am supplying an AC input sine wave with an amplitude of +-2 when the ADC0804 is already regulated at 0 and 5V what changes will I see in these volatage levels and how do I calculate it. I hope I was clear in explaining this question. Other than that I don't have any information about the frequency or any other parameter. Secondly I just wish to thank all the people that have replied so quickly and have been very helpful. It's good to see that this site is so very helpful It wouldn't be a bad idea, just as an aside, to clamp the capacitor outputs to the rails, i.e, place a fast schottky rectifier diode with its anode at GND and its cathode at the cap output, and another with its anode at the cap output and its cathode at Vcc. That will prevent accidentally overdriving the voltage input of the ADC. A series resistor between the CAP and that node wouldn't be a bad idea either. The clamping diodes protect the ADC, and the series resistor protects the diodes. 1000 ohms is probably a good estimate for that resistor. The devil's in the details of course, and you are, after all, supposed to work this out. RE |
| Topic | Author | Date |
| ADC0804 | 01/01/70 00:00 | |
| you can't | 01/01/70 00:00 | |
| I think what he means is ... | 01/01/70 00:00 | |
| More detail, please. | 01/01/70 00:00 | |
| How to measure an AC voltage? | 01/01/70 00:00 | |
| Measuring Ac | 01/01/70 00:00 | |
| Design Idea on the Subject | 01/01/70 00:00 | |
| More detail | 01/01/70 00:00 | |
an exercise for the student | 01/01/70 00:00 |