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Voltage regulator ICs (78xx series) provide a steady output voltage, as against a widely fluctuating input supply, when the common terminal is grounded. Any voltage about zero volt (ground) connected in the common terminal is added to the output voltage. That means the increase in the common terminal voltage is reflected at the output. On the other hand, if the common terminal is disconnected from the ground, the full input voltage is available at the output. This characteristic is utilised in the present circuit.... [read more]

This is a simplified version of the 4-Digit Keypad Controlled Switch. I have modified the design to reduce the complexity of the circuit - and the number of components required. As a result - the code is somewhat less secure. However, there should be lots of situations where it will still be adequate.... [read more]

This frequency doubler using a single 4069 hex inverter IC, a frequency doubler can be constructed to give an output pulse train whose frequency is twice that of a squarewave input signal.... [read more]

This small amplifier is constructed around the TDA2003 IC, capable of delivering 4Wrms at 4ohms. The TDA 2003 has improved performance with the same pin configuration as the TDA 2002. The additional features of TDA 2002, very low number of external components, ease of assembly, space and cost saving, are maintained.... [read more]

Short circuits or broken pcb tracks can be easily recognized by means of a Multimeter, but this tool can give wrong results when testing the efficiency of a transistor or diode, unless the device under test is unsoldered and removed from the pcb. A further shortcoming affecting such way of testing is the necessity to keep firmly the probes on the pins of the device under test and at the same time to turn the head continually to read the Multimeter display.... [read more]

It is a simple circuit of optical index of level of sound signals, adapted in various needs of user.... [read more]