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Water Level Indicator Circuit Schematic

When the water-level is below the steel rods, no contact is occurring from the metal can and the rods, which are supported by a small insulated (wooden) board. The small circuit built around IC1 draws no current and therefore no voltage drop is generated across R5. IC2A, IC2B and Q1 are wired as a window comparator and, as there is zero voltage at input pins #2 and #5, D3 will illuminate. When the water comes in contact with the first rod, pin #13 of IC1 will go high, as its input pins #9 to #12 were shorted to negative by means of the water contact.... [read more]

Multitone Siren

This multi-tone siren is useful for burglar alarms, reverse horns, etc. It produces five different audio tones and is much more ear-catching than a single-tone siren. The circuit is built around popular CMOS oscillator-cum-divider IC 4060 and small audio amplifier LM386. IC 4060 is used as the mult-itone generator. A 100µH inductor is used at the input of IC 4060. So it oscillates within the range of about 5MHz RF. IC 4060 itself divides RF signals into AF and ultrasonic ranges. Audio signals of different frequencies are available at pins 1, 2, 3, 13 and 15 of IC 4060 (IC1).... [read more]

Solar Cell Voltage Regulator

This device is designed to be a simple, inexpensive ‘comparator’, intended for use in a solar cell power supply setup where a quick ‘too low’ or ‘just right’ voltage indicator is needed. The circuit consists only of one 5V regulator, two transistors, two LEDs, five resistors, two capacitors, and one small battery. Although a 4-V battery is indicated, 4.5 V (3 alkalines in series) or 3.6 V (3 NiCd cells in series) will also work.... [read more]

Battery Powered Night Lamp

This circuit is usable as a Night Lamp when a wall mains socket is not available to plug-in an ever running small neon lamp device. In order to ensure minimum battery consumption, one 1.5V cell is used and simple voltage doublers drives a pulsating ultra-bright LED: current drawing is less than 500µA. An optional Photo resistor will switch-off the circuit in daylight or when room lamps illuminate, allowing further current economy. This device will run for about 3 months continuously on an ordinary AA sized cell or for around 6 months on an alkaline type cell but, adding the Photo resistor circuitry, running time will be doubled or, very likely, triplicates. IC1 generates a square wave at about 4 Hz frequencies. C2 & D2 form voltage doublers, necessary to raise the battery voltage to a peak value able to drive the LED.... [read more]

Video amplifier

Video amplifier with LM359N... [read more]

36 Watt Audio Power Amplifier Using TDA1562Q

It's based on a Philips class-H audio amplifier IC and can deliver 36W RMS OR 70W music power, all from a 13.8V supply. Our new Mighty Midget Amplifier can really pack a punch - around 36W RMS continuous into a 4-ohm load when using a 13.8V supply. However, it's the 70W of output power that it can deliver during dynamic (music) signal conditions that really make you sit up and take notice.... [read more]