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Ultrasonic sound wave can be generated using electronic circuit. This simple electronic circuit can generate an ultrasonic wave with frequency range of 12 to 50 kHz. Its very easy and quick to make this circuit. This circuit uses NE555 IC timer to drive a speaker. SPKR1 can be piezzo tweeter, etc. If you use a moving coil tweeter, then it is recommended to add a decoupling capacitor around 1uF-2.2uF/16V to block the DC voltage. For adding a circuit safety, you’d better insert a 1k resistor... Read Full Story

This relay circuit is controlled by almost any type of infrared remote controller. This circuit works on assumption that almost all remote controller use high frequency modulated infrared light. By filtering out un-modulated or low frequency modulated signal, this circuit will be able to remove any interference from ambient infrared light coming from other sources such as sun light, soldering  iron, or incandescent lamps. Here is the schematic diagram of the circuit: Read Full Story

The most common problem for infra-red (IR) remote control is the failure to transmit the pulsed infra-red light. The circuit shown in the schematic diagram below is an IR remote control handset tester. This device is very useful and easy to use, and could quickly identifying a faulty remote control handset. An operative remote control handset will generate a pulsed infrared light that falls upon D1, which creates a pulse waveform across R1. The signal from D1 is capacitively coupled to the... Read Full Story

An oscillator can be built using LC (inductor-capacitor) tank circuit. When we vary the capacity of the capacitor in LC tank circuit then the frequency of the oscillator will vary according to capacitance change.  The idea of this modulator is by employing a varactor (voltage-dependent variable capacitor) in the LC tank circuitry. As the capacitance is controlled by a voltage level, then it can be controlled using audio signal from microphone. A signal from direct microphone output will be... Read Full Story

Using the circuit depicted in the schematic diagram below we can monitor the heart pulses of patient. This circuit buffer and amplify the heart pulses, and the amplification bandwidth ranges from DC to 3 kHz. For the core of the isolation, a Burr-Brown BB3656 isolation amplifier integrated circuit (IC) is used in this circuit. With internal transformer inside, this integrated circuit give protection from inadvertent applications of defibrillation pulses while patient is being monitored. The... Read Full Story

The circuit below is a one-shot multivibrator. One shot multivibrator is also known as monostable multivibrator, or timer. The main function of such circuit is producing a fixed width pulse. The width of this pulse is determined by the component value selection at the time of designing the circuit. The main component of this circuit is the LM139, and this circuit only uses one section of quad LM139. The pulse width of this circuit is determined by the value of C2 and R1. When selecting the R1... Read Full Story

Sponsored Links Sometimes the output volume of amplifier is too high and hurts our ears. As well as hurting your ears, this incident could damage your loudspeaker. The circuit below can be used to protect both our ears and our loudspeakers from destructive output signal of amplifier, works by deactivating the amplifier when high level signal is detected. This circuit will disable the amplifier when the output volume of amplifier reaches the set level by detecting the paeak audio. This... Read Full Story

A pH meter circuit is basically an amplifier to boost a voltage signal which is produced by a pH probe. The pH probe itself is equal to a battery cell when submersed in the measured solution, producing a weak voltage and current signal. High input impedance requirement for pH probe while keeping the cost low, a 3130 CMOS op-amp give the solution for the signal conditioning circuit. The output of the probe, which is swinging from positive DC voltage to 0V for low pH to pH 7, and further to... Read Full Story

Sponsored Links Stroboscope is used to measure the speed of rotation, using the effect of strobed light, where a moving object will be perceived as stationary object if the light is strobed fast enough relative to the movement speed. When applied to a rotating object, a mark on the object will be perceived as not rotating if the frequency of the strobed light is exactly equal to frequency of the stroboscope, since the light only capture the mark exactly at the precise location where the it... Read Full Story

Sponsored Links Opening car’s door is very simple activity, and off course it’s just a daily activity which require no special skill. Almost nothing can go wrong, but forgetting to close the door when we doing or thinking on many tasks is a common thing. This can lead to many consequences, from as simple as air conditioner inefficiency to as dangerous as ridiculous accident when driving car with improperly closed door. The circuit shown in the following schematic diagram can alarm you for... Read Full Story