Posted by ATMAJA'Z

Only the 10 lower-priced electronic components is sufficient to create a noise of the siren voice / alarm anti-black attacks! Quite simple and suitable for electronic learning practice for beginners. Circuit scheme please look directly at the picture above, while the list of required components and the PCB to create 'noise' of this please see below (click image to enlarge view). I am sure you will not be difficult to assemble this mini alarm. Do not forget the required supply voltage is DC voltage between 3 to 6 volts only. If more than 6 volts issued voice was getting louder but the transistor TR2 will be hot and easily damaged. SKEMA RANGKAIN MINI ALARMThe diode D serves as a deterrent alarm oscillation frequency in-short by the power supply as well as a safety if the polarity of the power supply that we use installed upside down.
The rate lantingan we set the alarm to play the VR. If you want to change the frequency of the alarm can change the value of capacitor C1. The greater the value of C1 will lower the frequency tone alarm.