UM3561 - Simple Sound Effects Generator Circuit

This is a very simple. The IC UM3561 produces four differen sound effects, the output at Pin 3 being amplified by the transistor 2N2222. A 64 ohm loudspeaker can be substituted in place of the 56 ohm resistor and 8 ohm loudspeaker.

Skema Rangkaian Sound Effects Generator

The 2 pole 4 way switch controls the sound effects. Position 1 (as drawn) being a Police siren, position 2 is a fire engine sound, 3 is an ambulance and position 4 is a machine gun effect.

Note:
The IC sound generator UM3561 is now available in a kt from Maplin Electronics. Click here for the link.

Op-Amp 6-Line Audio Mixer Circuit

As with any audio mixer circuit, a slight loss is always introduced. The final summing amplifier has a gain of 2 or 6dB to overcome this. The Input line level should be around 200mV RMS.

Skema Rangkaian 6-Line Audio Mixer based Op-Amp

The mic inputs are amplified about 100 times or 40dB, the total gain of the mixer including the summing amplifier is 46dB. The mic input is designed for microphones with outputs of about 2mV RMS at 1 meter. Most dynamic microphones meet this standard.

The choice of IC op-amp is not critical in this circuit. Bipolar, FET input or MOS type op-amps can therefore be used; i.e 741, LF351, TL061, TL071, CA3140 etc. The power supply is a dual positive and negative supply, two 9 Volt batteries may be used as shown above or a power supply is recommended for longer periods of use

Water Activated Alarm Using IC 555 Circuit

This Water Activated Alarm circuit uses a NE555 timer wired as an astable oscillator and powered by the emitter current of the transistor BC109C. Under dry conditions, the transistor will from have no bias current and be fully off. As the probes get wet, a small current flows Between the base and emitter and the transistor switches on. A larger current flows in the collector circuit enabling the IC NE555 osillator to sound.

Skema Rangkaian Water Activated Alarm

Probe/contacts may use a non-reactive metal. Gold or silver plated contacts from an old relay May be Used, however a cheap alternative is to wire alternate copper strips from a piece of veroboard. These will eventually oxidize over but as very little current is flowing in the base circuit, the higher impedance the caused by oxidization is not Important. No base resistor is Necessary as the transistor is in emitter follower, current limit being the impedance at the emitter (the oscillator circuit).

Circuit from: www.epanorama.net

LM390 Simple 2-Way intercom Circuit

This is a very simple two way intercom circuit based on a LM390 audio amplifier circuit . the intercom circuit is a stand-alone electronic communications system intended for limited or private dialogue. For this circuit you can use a 8 ohms speaker, one for each station and require a 6 volts dc power supply. Gain control can be done by capacitively coupling a resistor (or FET) from pin 6 to ground.

LM390 Simple 2-Way intercom Circuit

LM390 Pin out

The LM390 Power Audio Amplifier is optimized for 6V, 7.5V, 9V operation into low impedance loads. The gain is internally set at 20 to keep the external part count low, but the addition of an external resistor and capacitor between pins 2 and 6 wil increase the gain to any value up to 200. The inputs are ground referenced while the output is automatically biased to one half the supply voltage.

Triangle and Squarewave Generator Using Op-Amp

The circuit shows a simple triangle and squarewave generator using a common LM1558 dual op-amp to produce very low frequencies to about 10 KHz. The time interval for one half cycle is about R*C and the outputs will supply about 10mA. Triangle amplitude can be altered by adjusting the 47k resistor and waveform offset can be removed by adding a capacitor in series with the output.

Absolute Maximum Ratings Of Op-Amp LM1558 IC

• Supply Voltage ±22V
• Power Dissipation 400 mW
• Differential Input Voltage ±30V
• Input Voltage (Note 3) ±15V
• Operating Temperature Range −55°C to +125°C
• Storage Temperature Range −65°C to +150°C
• Lead Temperature (Soldering, 10 sec.) 260°C