Once the voltage of C1 reaches the trigger voltage of D1, which is forward biased, current flows through D1. (why at that trigger voltage?
• The current flowing through D1 establishes a source current from Q2b to Q2e. This in turn causes a greater current to flow from collector (Q2c) to the emitter (Q2e), thus allowing Q1b to see positive. • The current flowing from the Q2c to Q2e, causes a similar flow of current in Q1 from Q1e to Q1b, since Q1b is now positive. (Recall, that if a small voltage is applied to the base — enough to remove the depletion layer in the emitter-base junction, current flows from emitter to base as in a diode) • This small amount of current through Q1e to Q1b induces a larger flow of current from the emitter (Q1e) to the collector (Q1c). • The current flowing from Q1e to Q1c goes throgh motor, M, causing it to go spin. • EVENT – SE triggered, Beginning of discharging cycle • EVENT – Motor turns on • While the current is flowing through M, the voltage across C1 falls • EVENT – voltage across C1 falls below trigger point of D1 • The base of Q2, Q2b is being feed current by way of D1 and also by way
