Regulated +15 -15 Volts Symmetric Power Supply From 12 Volt Transformer
If you need +-15 Volts supply and you have only a standard 12V AC transformer, don’t be hurry to buy a new one with center tap, you can use your old transformer! The schematic diagram of this circuit is shown in the figure below. The voltage before entering the regulator IC 7815 and 7915 might …[Read More]
Simple Automatic Nicad (NiCd) Battery Charger
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 …
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, …[Read More]
Bulk Transistor Tester – An Easy Transistor Gain Classifier
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 …[Read More]
Capacitance Meter Using 555 Oscillator
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 …[Read More]
Very Simple Touch Switch Using 4050 CMOS Buffer
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 …[Read More]
Simple 8 Watt Audio Power Amplifier Using TDA 2030
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 …[Read More]
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