≥100 dB @30cm
-40 ～ +85 ℃
-40 ～ +90 ℃
General beep alarm driver circuit settings
Generally in some simple buzzer alarm, often buzzer sound or light-emitting diode to achieve the warning signal. Due to small buzzer drive current, simplifying the circuit design.
Transistor drive the buzzer circuit - Figure 7
In the picture above, HA is the audible indicator, using low voltage (3V) buzzer, its working current only needs a dozen milliamps. VT chooses 9013, fe ≈ 200, the bias resistor R is 15kΩ, VT base current IB is about 0.1mA, the collector current IC is about 10mA, at this moment VT has already been saturated and turned on, between its collector and emitter The voltage VCE is only 0.05V.
The circuit in Figure 7, the switch S replaced by reed switch, it is transformed into magneto-acoustic circuit.
The circuit in Figure 7 R reduced to 10kΩ, control switch S replaced by photosensitive resistor or photodiode, it becomes a light-controlled sound circuit.
What is the role of these circuits? Can be used as a safe burglar alarm, open the door, the magnet left the dry reed or safe light alarm.
If necessary, the magnetron and photosensitive element can be biased under the bias to satisfy the reverse phase control.