Sight n sound metronome

  
Precise, adjustable control of beats per minute from a largo of 18 to a frenzied, high presto of 500, These beats are produced acoustically through a speaker. A light flashes at the same rate. When SW1 is closed, CI begins to charge through Rl and R2. Cl will eventually reach a voltage at which the emitter of unijunction transistor is switched on, `dumping` the energy stored in Cl into an 8 ohm speaker. To produce a distinct `plop`, brief pulses across T2 secondary drive Q2 into conduction
Sight n sound metronome - schematic

The extra gain of Q3 and Q4 are sufficient to briefly switch LI on, then o£f; as the pulse wave pas-ses. Capacitor C2 "stretches" the puise slightly to overcome the thermal inertia of the lamp, so that a bright flash occurs,.




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