Chapter 4. Experiment 4: Measuring Light
Remember that you will find components for each experiment listed at the back of the book. See Appendix B.
Check the very simple schematic in Figure 4-1, which looks quite similar to the circuit in Figure 2-8. You can add it as a separate circuit to your breadboard, without dismantling the circuit that you built in Experiment 3. Just move the phototransistor and the resistor farther down your breadboard.
The resistor that I have chosen is 3.3K, because I want to get the widest possible range of voltages from the phototransistor emitter, and I found ...