Hi,
So I'm using an OP amp Tl072 to amplify a blue LED output as a way to use a Blue LED as a color sensor.
I have the op amp itself wired up like this: https://blog.adafruit.com/wp-content/uploads/2012/05/Screen-Shot-2012-05-29-at-8.18.31-PM.png
Plus, a few other stuff so that I can read the voltage output with a multimeter....
Anyhow, the problem is this
Say at time 0, Voltage (dark) = 1V. Voltage (light)= 2V.
Wait 10 seconds, V(dark) = 1V, but voltage (light) = 1.9V.
Wait 60 seconds (dark) = 1V but voltage (light) = 1.5V.
Wait a long enough time, dark = 1V, light = 1.01V.
Somehow over time, the amplification is completely reduced to near 0.
And this decreasing voltage happens as long as the battery is still connected (18V input). Once I disconnect it and wait a while, it sort of resets back to time 0.
How do I keep the voltage constant as time 0?
So I'm using an OP amp Tl072 to amplify a blue LED output as a way to use a Blue LED as a color sensor.
I have the op amp itself wired up like this: https://blog.adafruit.com/wp-content/uploads/2012/05/Screen-Shot-2012-05-29-at-8.18.31-PM.png
Plus, a few other stuff so that I can read the voltage output with a multimeter....
Anyhow, the problem is this
Say at time 0, Voltage (dark) = 1V. Voltage (light)= 2V.
Wait 10 seconds, V(dark) = 1V, but voltage (light) = 1.9V.
Wait 60 seconds (dark) = 1V but voltage (light) = 1.5V.
Wait a long enough time, dark = 1V, light = 1.01V.
Somehow over time, the amplification is completely reduced to near 0.
And this decreasing voltage happens as long as the battery is still connected (18V input). Once I disconnect it and wait a while, it sort of resets back to time 0.
How do I keep the voltage constant as time 0?
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