What does the project present?
The DIY electronic kit presented in this article, electronically generates an electrical signal which, transformed into sound by a speaker, resembles that generated by classic sirens. The diagram includes two stable circuits, a training circuit and a power amplifier.
How does the assembly work?
The stable tilting circuit (CBA) made with transistors T1 and T2 has a very low oscillation frequency, it being the one that determines how often the "tone" of the siren will change.
The pulses obtained from this CBA supply the formation circuit consisting of diode D, resistor R5 and capacitor C3. At the terminals of the capacitor C3 the voltage will increase with the speed determined by the time constant R5, C3 while T2 is blocked. During the saturation of the transistor T2, the diode D will be blocked and the voltage at the terminals of C3 will slowly decrease as a result of the discharge R6 which is part of the second CBA (stable tilting circuit).
CBA made with transistors T3 and T4 generates the "tone" of the siren. Its oscillation frequency depends on the voltage at the terminals of capacitor C3 varying depending on its value. The signal thus obtained is applied to the power amplifier made with the transistor T5 which can supply a speaker.
Mounting characteristics
- Supply voltage: Vdc - between 9V and 12V (batteries or DC voltage source)
- Current absorbed from the source: Imax = 200 mA
- Speaker impedance: between 3 and 16 Ohm
- Minimum speaker power: 0.25W
List of required components (includes recent equivalents):
- T1, T2, T3, T4 - transistors - (AC 180, EFT 321 or BC 557)
- T5 - transistor - (AC 180K or BC 557)
- C1, C2, C6 - capacitors - 150uF (min. 12 Vdc)
- C3 - capacitor - 220uF (min. 12 Vdc)
- C4, C5 - 47nF (min. 12 Vdc)
- R1, R4 - resistors - 1.2KOhm (min. 0.25W)
- R2, R3 - resistors - 18KOhm (min. 0.25W)
- R5 - resistor - 12KOhm (min. 0.25W)
- R6, R8 - resistors - 22KOhm (min. 0.25W)
- R7, R9, R11 - resistors - 470 Ohm (min. 0.25W)
- D1 - Diode - EFD 107 or 1N34A
- printed wiring or breadboard test board
- tin or connecting threads
Download the original IPRS leaflet Baneasa 7802
For a better understanding of the operation of the circuit we will need electronic scheme presented below:
In order to carry out this project in our own laboratory, we will also need printed wiring PCB layout From lower:
Many of you are probably wondering how this DIY electronic kit was packaged or distributed. Below I have attached a picture with packaged product (new). Thank you Mr. Marius Balauta for providing the picture.
