Small power converter

The converter enables an existing positive supply voltage to be raised, to be lowered, or to be changed into negative potential. The new voltage is electrically isolated from source by a DIY transformer wound on a G2-3FT12 toroid. The primary winding consists of 30 turns. The number of secondary turns, n, is calculated from n= […]

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Virtual ground

Virtual ground: Often only a single power supply is available for an opamp circuit. Since such circuits normally require a double supply, this means that in some way the available supply has to be converted. This is normally done by a potential divider and capacitor across the single supply. sometimes followed by an ancillary opamp.[…]

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Inductive proximity switch

Inductive proximity switches are used for instance for measuring motor speeds or determining the position of metal objects. They do not suffer from mechanical wear or contacts that spark. The latter is particularly important in spaces where explosive materials are stored. Virtually all commercial proximity switches are constructed as shown in fig 1. An inductor[…]

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CB-to-SW down converter

This converter enables long distance (DX) reception of AM or SSB stations in the 27-MHz citizens’ band (CB) on a short-wave or medium-Wave radio (note, though, that AM or SSB modulation in the 27-MHz CB band is no longer allowed in a number of countries). The converter consists of a prestage, T1, and a mixer/oscillator,[…]

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S-meter for short-wave receivers

Some radio amateurs are very keen on accurate RST reports, others (mostly the VHF/UHF fraternity) never look at the S-meter on the receiver, and are satisfied as long as they can hear the other station. This circuit is the first group. Traditionally, one S-point corresponds to a 6-dB increase in signal strength, while ‘S9’ is[…]

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Simple d.c.-to-d.c. converter

To keep the converter simple, it contains no preset controls, which means that the level of the output voltage is dependent to some degree on the load. In theory, the output level is twice the level of the input voltage, but, owing to losses in the converter, that level cannot be attained. The main losses[…]

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