Sound Alarm Generator | Electronic Project Circuits

Posts Tagged ‘Sound Alarm Generator’

Bell Alarm

If you use a lamp with a motion sensor for outdoor lighting, the original electrical switch is actually no longer necessary. If you replace the switch with the circuit described here, an acoustical signal will be generated each time the outdoor lamp is switched on. It’s thus somewhere between an alarm and a doorbell. The operating principle is simple. A circuit that causes a voltage drop of only a couple of volts is connected in series with the lamp. As the circuit needs a DC voltage, the current for the lamp is passed through a bridge rectifier.

The voltage drop across the circuit is determined by R1. The function of C1 is to smooth the raw DC voltage. Note that this is not an example of peak rectification, but instead of averaging. For this reason, the voltage on C1 is lower than you might expect. Ultimately, the DC voltage on C1 reaches the same value as the average voltage across R1. For example, consider what happens with a 100-W lamp. For convenience, we can assume that the lamp has a resistance of 529 R. If we ignore the voltage across the diodes and the voltage across R1, the current is approximately 0.39 A on average (not 0.43 A).

This is because the average mains voltage is only 207 V = (230 × v2) ÷ (p/2). This yields a voltage of approximately 8.5 V on C1. As the buzzer and T1 only draw a few milliampères from C1, in practice the voltage will differ from this value by at most a few tenths of a volt. Here you should use a DC buzzer with a large operating voltage range. A good example is the CEP-2260A, which has a voltage range of 3–20 V (available from Digi-Key and other online sources). The charging time of C2 determines how long the buzzer remains energised, and here it will be a few tenths of a second.
Depending on how much current the buzzer draws, you can increase the value of R2 in order to extend the time (this is certainly necessary with the above-mentioned buzzer type). Depending on the lamp power, you can consider adjusting the value of R1. This will certainly be necessary if you use a 150-W lamp or larger. In this case, cut the value of R1 in half, primarily because the power dissipation will otherwise be too large. In the example described here, it is around 3 watts. The bridge rectifier also deserves special attention.

A large current can flow briefly when the lamp is switched on ‘cold’. A 250V, 1.5-A bridge rectifier is adequate for a 100-W lamp, but heavier-duty diodes are necessary with higher lamp power – such as the 1N5408 (1000 V / 3 A). Due to the heat generated by R1, make sure that R1 is located a certain distance away from the other components in the assembled circuit. Also bear in mind that the entire circuit is connected to mains potential. Never make any adjustments while the circuit is connected to the mains! It’s thus a good idea to test the circuit before fitting it into the switch box.

Read more: http://www.extremecircuits.net/2010/05/bell-alarm.html

Be the first to comment - What do you think? Posted by admin - February 23, 2011 at 6:59 am

Categories: Alarm systems Tags: electronic bell, Sound Alarm Generator

Sounds train whistle with ic 556

When pressed Sw1 will train noise emitted through the speakers. Created for use as sound alarms and other.Using the IC 556 is a great circuit.
This circuit features a small. Because it uses a single IC. Working out sound speakers directly.
Operation of the circuit.When connecting the power supply.Low frequency generator circuit to start out the 5th pin. A separate section to the 9 pin. To the speaker driver.Frequency depends on the R2, C2.The signal from the 5 pin is connected to the 8 pin.The R6, C1 to reset the circuit delay.
When the reset pin 8 signal. High frequency signal generators will come out at pin 9 of IC1. So frequencies that are characteristic of sound, low frequency. Then a high frequency.

Be the first to comment - What do you think? Posted by admin - September 22, 2010 at 8:10 am

Categories: Alarm systems Tags: audio generator circuit, NE556, Sound Alarm Generator

Power Buzzer by tda2030

How often on average do you have to call members of your family each day to tell them that dinner is ready, it’s time to leave, and the like? The person you want is usually in a different room, such as the hobby room or bedroom. A powerful buzzer in the room, combined with a pushbutton at the bottom of the stairs or in the kitchen, could be very handy in such situations. The heart of this circuit is formed by IC1, a TDA2030. This IC has built-in thermal protection, so it’s not likely to quickly give up the ghost. R1 and R2 apply a voltage equal to half the supply voltage to the plus input of the opamp. R3 provides positive feedback. Finally, the combination of C2, R4 and trimmer P12 determines the oscillation frequency of the circuit.

The frequency of the tone can also be adjusted using P1. There is no volume control, since you always want to get attention when you press pushbutton S1. Fit the entire circuit where you want to have the pushbutton. The loudspeaker can then be placed in a strategic location, such as in the bedroom or wherever is appropriate. Use speaker cable to connect the loudspeaker. Normal bell wire can cause a signi?cant power loss if the loudspeaker is relatively far away. The loudspeaker must be able to handle a continuous power of at least 6 W (with a 20-V supply voltage).

The power quickly drops as the supply voltage decreases (P = Urms 2 / RL). The power supply for this circuit is not particularly critical. However, it must be able to provide sufficient current. A good nominal value is around 400 mA at 20 V. At 4 V, it will be approximately 25 mA. Most likely, you can find a suitable power supply somewhere in your hobby room. Otherwise, you can certainly ?nd a low-cost power supply design in our circuits archive that will ?ll the bill!
Author: G. Baars
Copyright: Elektor Electronics
Source: http://www.extremecircuits.net/