Timeline for Not accurate readings when connecting OpAmp AD822 to ADC MCP3008
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 23, 2021 at 8:31 | vote | accept | Samboff | ||
| Mar 16, 2021 at 12:37 | vote | accept | Samboff | ||
| Mar 16, 2021 at 12:37 | |||||
| Mar 13, 2021 at 13:14 | comment | added | Samboff | I'm using the BPW34S from Vishay. And I would read light intensities of up to 2000W/m^2 | |
| Mar 12, 2021 at 16:48 | comment | added | jusaca | Out of curiosity: What kind of diode do you use to get such low resistor values? With 178 Ohm you need more than 5mA of photo current to get 1V at the ADC. | |
| Mar 12, 2021 at 16:47 | comment | added | jusaca | But to be honest I have no further ideas where the problem might be... | |
| Mar 12, 2021 at 14:39 | comment | added | Samboff | Hi! Thanks for the comment. I got the value from the Analog Devices Photodiode Wizard. For my usage, as I should get high intensities of Light, Rf = 178 Ohm, and Cf = 1300pF. I changed the Rf to a higher value to test it with ambient light and flashlights. I changed everything back, so Rf = 178 Ohm. However I still get similar fluctuations in my MCP3008. Often getting 0V as output | |
| Mar 12, 2021 at 13:48 | comment | added | jusaca | I extended the answer by a another problem that may result in the fluctuations you see. | |
| Mar 12, 2021 at 13:47 | history | edited | jusaca | CC BY-SA 4.0 |
added 943 characters in body
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| Mar 12, 2021 at 13:07 | comment | added | Samboff | Thank you for the info about the Voltage. If I understand you correctly, I should connect the decoupling as I showed in my edited post? Because if that is the case, I still get a lot of fluctuations on my ADC | |
| Mar 12, 2021 at 11:27 | history | answered | jusaca | CC BY-SA 4.0 |