Simple Adjustable DC - DC Converter

It's easier to generate DC from AC mains supply using a transforme and some diodes but the difficult part comes when we need to regulate the supply to feed sensitive devices such as mobile phones. Here's a versatile DC to DC coupler that 'll give you regulated fixed dc output voltages like 5V to charge mobile phone, 12V for external hard drives etc. You may use a 19V laptop adapter to route various voltages such as 5V , 6V, 12V from it.

Automatic Muting Circuit For Audio Systems

Here's a circuit diagram of automatic muting for audio systems using IC LB1403. The signal from pre-amplifier such as LA3160, LA3161 or HA1032 is connected to the base of the amplifier transistor BC548 (T1). Variable resistor VR1 is used to control the gain of input signal.

Digital Fan Regulator Circuit

The circuit presented here is that of a digital fan regulator, variable  to provide five speed levels as catered for in ordinary fan regulators. The circuit of ceiling fan controller makes use of easily available components. An optional 7-segment display with its associated electronic circuitry has been provided to display your choice of fan speed.

Water Tank Level Meter

The water-tank level meter described here is very simple circuit diagram and useful for monitoring the water level in an overhead tank (OHT). The water level at 30cm intervals is monitored and continuously indicated by LEDs arranged in a meter-format. When all the LEDs are ‘off’, it indicates that the OHT is empty. When the water level reaches the top limit, the whole LED-meter begins to flash. The height at which the level-sensing electrodes are fitted is adjustable. Thus, the minimum and maximum level settings may be varied as desired. The range of the meter can also be enlarged to cater to any level. No special or critical components are used. CMOS ICs are used tolimit the idle current to a minimum level.

Powerful Pest Repeller Circuit

Most of the electronic pest repeller circuits have a major drawback of low power output hence their effectiveness suffers. The ultrasonic pest repeller circuit described here generates powerful ultrasonic signals therefore efficient to repel pests like mosquitoes. In addition to the ultrasonic frequency oscillator, we use a  separate push-pull power amplifier and transformer  to boost ultrasonic signals.

Tips to Extend Life Of Solar SMF Battery

Off-grid photo voltaic solar power equipment require a battery to store the energy accumulated during sunny hours for use at night. In most applications lead acid batteries are proffered as these are maintenance-free and do not emitany harmful gas while charging.

Bass And Treble Circuit Using Transistor

 This circuit diagram for bass and treble control is effective and using low cost components.

Modern audio frequency amplifiers provide flat frequency response over the whole audio range from 16 Hz to 20 kHz. To get faithful reproduction of sound we need depth of sound, which is provided by bass (low notes). Hence low-frequency notes should be amplified more than the high-frequency notes (treble). To cater to the individual taste, and also to offset the effect of noise present with the signal, provision of bass and treble controls is made. The combined control is referred to as tone control.

Digital Water Level Indicator

This digital water level meter circuit indicates up to 65 discrete water levels in the overhead tank (OHT). This
helps to know the quantity of water in the OHT quite precisely. The circuit is specially suited for use in  apartments, hostels, hotels, etc, where many taps are connected to one OHT. In such cases, if someone for gets to close the tap, this circuit would alert the operator well in time.