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

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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.

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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

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Rangkaian Alat Bantu Pendengaran

This circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume, avoiding to bother relatives and neighbors. Even if you have a faultless hearing, you may discover unexpected sounds using this device: a remote bird twittering will seem very close to you.

Skema Rangkaian Alat Bantu Pendengaran

The heart of the circuit is a constant-volume control amplifier. All the signals picked-up by the microphone are amplified at a constant level of about 1 Volt peak to peak. In this manner very low amplitude audio signals are highly amplified and high amplitude ones are limited. This operation is accomplished by Q3, modifying the bias of Q1 (hence its AC gain) by means of R2.
A noteworthy feature of this circuit is 1.5V battery operation.

List Component

P1        : 22K   Log. Potentiometer
R1,R9     : 10K
R2        : 1M
R3        : 4K7
R4,R7     : 100K
R5        : 3K9
R6        : 1K5
R8        : 100R
C1,C2     : 100nF
C3,C6     : 1µF/63V
C4        : 10µF/25V
C5        : 470µF/25V
D1        : 1N4148
Q1,Q2,Q3  : BC547
Q4        : BC337
MIC1      : electret microphone
SW1       : SPST Switch
J1        : Stereo 3mm. Jack socket
B1        : 1.5V Battery (AA or AAA cell etc.)

Circuit from: www.sound.westhost.com

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30W Mini Mosfet Amplifier

This mini mosfet amplifier project was a sort of challenge: designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality. The Power Amplifier section employs only three transistors and a handful of resistors and capacitors in a shunt feedback configuration but can deliver more than 18W into 8 Ohm and up to 30W into a 4 Ohm load.

Skema Rangkaian Mini Mosfet Amplifier

To obtain such a performance and to ensure overall stability of this very simple circuitry, a suitable regulated dc power supply is mandatory. This is not a snag because it also helps in keeping noise and hum of the preamp to very low levels and guarantees a predictable output power into different load impedances. Finally, as the amplifier requires only a single rail supply, a very good dc voltage regulator capable of supplying more than 2 Ampare/40V can be implemented with a few parts also.

How to Setup of this Amplifier Circuit

• Connect the Power Supply Unit to the Power Amplifier
• Rotate the cursor of R4 fully towards Q1 Collector.
• Set the cursor of R3 to about the middle of its travel.
• Connect a suitable loudspeaker or a 8 Ohm 20W resistor to the amplifier output.
• Connect a Multimeter, set to measure about 50V fsd, across the positive end of C5 and the negative ground.
• Switch on the supply and rotate R3 very slowly in order to read about 23V on the Multimeter display.
• Switch off the supply, disconnect the Multimeter and reconnect it, set to measure at least 1Amp fsd, in series to the positive supply (the possible use of a second Multimeter in this place will be very welcomed).
• Switch on the supply and rotate R4 very slowly until a reading of about 120mA is displayed.
• Check again the voltage at the positive end of C5 and readjust R3 if necessary.
• If R3 was readjusted, R4 will surely require some readjustment.
• Wait about 15 minutes, watch if the current is varying and readjust if necessary.
• 12. Please note that R3 and R4 are very sensitive: very small movements will cause rather high voltage or current variations, so be careful.
• 13. Those lucky enough to reach an oscilloscope and a 1KHz sine wave generator, can drive the amplifier to the maximum output power and adjust R3 in order to obtain a symmetrical clipping of the sine wave displayed.

List Componet

R1    : 2K2  1/4W Resistor
R2    : 27K  1/4W Resistor
R3,R4 : 2K2  1/2W Trimmers Cermet or Carbon (or 2K)
R5    : 100R 1/4W Resistor
R6    : 1K   1/4W Resistor
R7,R8 : 330R 1/4W Resistors

C1    : 22µF/25V
C2    : 47pF/63V
C3,C4 : 100µF/50V
C5    : 2200µF/50V

Q1    : BC550C  NPN Transistor
Q2    : IRF530  N-Channel Hexfet Transistor (or MTP12N10)
Q3    : IRF9530 P-Channel Hexfet Transistor (or MTP12P10)

Circuit From: www.redcircuits.com

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9 Volt Portable Headphone Amplifier Circuit

Here I present a very simple and powerful headphone amplifier Circuit using NE5534/2 . In addition to the IC NE5534/2, the circuit uses only few passive components and can easily generate a lot of sound from even the most inefficient headphones and there will be no compromise for the quality.

Circuit of 9 Volt Portable Headphone Amplifier

The 5534/2 is a low-distortion, low-noise device, having also the ability to drive low-impedance loads to a full voltage swing while maintaining low distortion. Furthermore, it is fully output short-circuit proof. Therefore, this circuit was implemented with a single 5532 chip forming a pair of stereo, inverting amplifiers, having an ac gain of about 3.5 and capable of delivering up to 3.6V peak-to-peak into a 32 Ohm load (corresponding to 50mW RMS) at less than 0.025% total harmonic distortion (1kHz & 10kHz).

List Component of Portable Headphone Amplifier

P1 = 22K
R1 = 18K
R2 = 68K
R3 = 68K
R4 = 68K
R5 = 18K
R6 = 68K
C1 = 4.7uF/25v
C2 = 4.7uF/25v
C3 = 22pF
C4 = 220uF/25v
C5 = 220uF/25v
C6 = 4.7uF/25v
C7 = 22pF
C8 = 220uF/25v
J1 = 3.5mm Stereo Jack
B1 = 9V Alkaline Battery
IC1 = NE5532 or NE5534
SW1 = SPST Toggle Switch

Circuit From: www.redcircuits.com

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