Free electronic circuit design and schematic diagram
Many cheap battery chargers usually assume that charging the battery slowly is OK although the battery is already full of charges. All they do is usually charging the battery with constant current no matter if the battery is almost completely discharged or has been fully charged. Off course the battery wouldn’t be damaged immediately after few charging cycles, but actually […]
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You can use a humidity sensor to give an alert of boat leakage, or when your books start being flooded by heavy rain attack on your broken roof, or anything you can imagine. A simple humidity sensor (a humidity probe) can be constructed using two copper wires placed as close as possible to each other, but no touching. This simple […]
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This transistor tester is very helpful if you need to sort bulk transistors. In some market, if you know where to find it, sometimes you can get transistors sold in kg unit, not in single peaces unit. You can buy 1 kg of transistors with really cheap prices. Don’t be too happy right now because you have to be careful, […]
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The frequency formula of 555 oscillator is popularly known. For a known resistors and capacitor, the frequency can be determined by a formula. From the math logic, if the frequency and the resistors are known, then an unknown capacitor could be determined by the inverse of the formula. Anyone who has a frequency counter are able to use the following […]
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Many efforts has been made to make simpler circuit, and here is one result, a very simple touch switch. You can build up to 6 similar circuit using only one 4050 chip. If you touch the “on” pad, the output will be on on remains on until you or some one the “off” pad. Here is the circuit schematic diagram: […]
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Using only a single chip and few passive components, you can build 8-14 Watt audio power amplifier using TDA2030 chip. Here is the circuit schematic diagram: If you use 4 ohm speaker then you get 14 Watt output power, and around 8 Watt if you use 8 ohm loudspeaker. Make sure the 100n and 100u capacitor is wired as close […]
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Don’t worry if you need a symmetric power supply and you don’t have a center tapped transformer. The circuit below solve your problem. You can see the second bridge diode is powered via capacitor decoupling, so it’s DC isolated. Because it’s DC isolated, we can connect the ground together to form a symmetric supply. Because the second rectifier is powered […]
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