The first electronic gong circuit presented below simulates the sound of a bell or a gong; The circuit consists of a resonant filter, built around IC2 and IC3, which rings at its resonant frequency when a short pulse is fed to the input.
In this circuit the trigger pulse is provided by a 555 timer connected as a multivibrator, but other trigger sources may be used depending on the application.
The character of the sound is influenced by two factors: the ‘Q’ of the filter, which may be varied by changing the value of R2, and the duration of the trigger pulse, which may be adjusted using P 1.
The repetition rate of the trigger pulse, i.e. the rate at which the gong is ‘struck’. may be varied. using P2. In order to drive a loudspeaker, the output of the electronic gong circuit must be fed through an audio amplifier. The output level may be varied from 0 to 5V by means of P3.
PCB Design
Electronic Gong Circuit using IC 4093
The discussed second electronic gong circuit initiates a couple of solenoids in sequence to affect two chimes or gongs one while your doorbell is pushed. another whenever it is released.
Any time pushhutton S1 the front doorbell is first pushed C2 immediately charges. This stops switch rebound. that might result in solenoid L2 to activate ahead of time L2 is susceptible to trigger briefly on power-up).
IC1a and IC1b form a positive-edge-triggered monoostable timer to ensure whenever pins l and 2 go high TR1 conducts for a tiny proportion of a second. triggering solenoid L1.
Diode D1 inhibits back-EMF. that could eliminate IC1 specifically. Any time pushhutton S1 is released C2 discharges by means of R1 IC1c and ICld. with TR2. form a positive-edge-triggered monostable timer so that whenever pin 8 goes low TR2 stops to conduct.
What this means is that TR3's gate should go high and TR3 conduct hence triggering solenoid L2 for a portion of a second.
D2 is for a second time provided to reduce back-EMF. Except if a huge battery is employed for B l Cl is necessary to supply the ‘whack' needed for solenoids L1 and L2.
N11-polarised capacitors are advised for C2 to C4 to put away concerns regarding polarity. Nevertheless polarity is displayed in the circuit just in case the constructor is merely competent to find electrolytic capacitors of this value.
In the event the pulses that stimulate L1 and L2 aren't adequately long the values of R2 and R3 may be enhanced and vice versa.
In case TRI and TR3 are not found. close variation may be used. Equivalents must be picked carefully for TR2 because this can be a miniature MOSFET. Although an NPN bipolar transistor could possibly be utilized here the value of R4 ought to in that case be lowered to say 1K thus decreasing power usage on standby.
Preferably solenoids L1 and L2 will be 12V push-action types or pull-action varieties which may have a drive pin on the back. On the other hand plain pull-action forms must function if they happen to be pressing the chimes or gongs once the circuit reaches relaxation (they might then pull back rebound and hit).
Smaller motors with hammers connected could also be used along with appropriate series resistors in case necessary.
