Electronic bell-push

A solid-state bell-push is far more robust than the usual mechanical type. The touch contact may be made from an audio socket, which has a high insulation resistance and is practically indestructible. The inverting (-) input of IC1 is at half the supply voltage via R4-R5, while the non-inverting input is at earth potential via[…]

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Halogen light switch

Halogen lamps are rightly popular because they give a good light and have an excellent efficiency. Unfortunately, they tend to be costly. Moreover, they often give up the ghost when they are switched on because they then draw a very high current (some ten times normal, equivalent to roughly a hundred times their normal power[…]

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Fog light switching

Many cars are not factory-fitted with fog light and consequently, there is often no provision for switching. optionally added ones. However, since in most European and North American countries, it is now illegal to drive on sidelights and many cars still have a switch for these. the fog lights may be operated with this. The[…]

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DC-motor regulator

The regulator shown in the diagram enables the speed of a d.c. motor to be set over a wide range. Although the most frequently used method for achieving this is pulse-width modulation, in the present design pulse position modulation (also called pulse time modulation) is used. That is, rectangular modulator IC1 always switches the motor on for[…]

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Single-chip temperature control

The UAA2016 from Motorola lends itself admirably to making a proportional mains-operated temperature control. A resistor with negative temperature control (NTC), R3, which must have a value of about 100 (12 at 25 °C, serves as a sensor. In the diagram, the heating element is a 100 W light bulb, which generates enough heat for[…]

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