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Topic: Using phototransistors - hardware check. (Read 2526 times) previous topic - next topic

dc42

From the figures you posted at the start, and given that you are supplying the phototransistor from a separate 1.5v supply, I suspect that what you were measuring was not change in light intensity but the reduction in Vcc as you increase the average LED current. Also, 68 to 470 ohm sounds way too low for the series resistor to me. What happens if you repeat the measurement but put something between the LED and phototransistor to block the light?
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

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