Drum beat Simulator Metronome

Although the simple metronome desribed in project one would suffice in most cases, it might be necessary in some cases for a more real lifelike beat like that of a bass drum to be essential. The circuit given here achieves just that but needs an additional amplifier to make its signal useful. The complete diagram is given in figure 2. Unijunction transistor Q1 has been wired as a conventional relaxation oscillator This particular UJT is not critical and any UJT may be used so far as the connections for the particular UJT used should be checked. Potentiometer R3 is a pre-set control for controlling the maximum and minimum beat rates of the 

Drum beat Simulator Metronome circuit diagram

Panel control R4. These resistors along with R5 control the charging rate of capacitor C1 and hence the pulse repetition rate at the emitter of UJT. Pulses produced at E are passed through a pulse shaping network R6.C3 and R7 to achiee the desired transient characteristics of a typical bass drum. The shaped pulse is applied through R8 to a bas drum simulating circuit built around Q2 Wired as a Twin-T oscillator. The output is taken via C7 to an audio amplifier. The setting procedure for this is very simple. With power applied to the circuit adjust R13 until an oscillation starts appearing at the amplifier output. Then back up the preset till the oscillation just ceases to oscillate on itself. Preset R3 should be adjusted next tc achieve the minimum desired beat rate with potentiometer R4 fully open ( so that it gives its maximum resistance). An optional foot-switch may be added by breaking the connection between point E of UJT and the junction of R5,R6 and C1. the circuit will operate only when these two points are connected.