Automatic power off

The power off circuit ensures that any load is automatically removed from a battery. It is particularly useful in cars so that if the driver forgets to switch off the headlights, he does not return to a car with a flat battery a couple of hours later. The only operating control is a spring-loaded change-over[…]

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Simple power supply concept

THE best-known alternatives to a ‘quick and dirty’ power supply are the three-pin fixed voltage regulator and the Zener-plus-transistor combination. While these basic circuits will suit a good many applications, they do have their limitations, which can be frustrating at times. For example, most types of fixed voltage regulators are limited to an output current[…]

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Switched 5 V supply

To derive a 5 V line from, say, a 15-25 V supply, National Semiconductor’s LM1575 or LM2575 is ideal. These switched 5-V regulators need only a choke, a freewheeling diode and a couple of electrolytic capacitors. In fact, they go a long way to prove that the industry has overcome most of the problems switched[…]

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Audible continuity tester

  Whatever the latest trend in digital multimeters. no electronics workshop is complete without a continuity tester for fast and reliable testing of connections, components, and PCB tracks. The little instrument discussed here is an audible continuity tester whose output frequency is determined by the resistance measured. Handheld and extremely simple to use, the tester[…]

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