This circuit was developed to power an AVR microcontroller from a 12 V leadacid battery. The regulator itself draws only 14 μA. Of course, there are dedicated ICs, for example from Linear Te... Read more
Circuits have been published on earlier occasions that keep an eye on the telephone line. This simple circuit does it with very few components and is completely passive. The operating princi... Read more
This circuit is innovative in more than one way and therefore belongs per se in Elektor’s Small Circuits Collection. Firstly, it demonstrates how the combination of a blue and a white LED ca... Read more
This circuit was designed to produce an audible alarm when the mains power is interrupted. Such an alarm is essential for anyone whose livelihood depends on keeping perishable foodstuffs in... Read more
UV (ultra-violet) LEDs can produce eyecatching effects when their light is allowed to interfere with certain colours, particularly with reflected light under near-dark conditions. Also try s... Read more
Lots of consumer electronic equipment like TV sets, VCRs, CD and DVD players employs infrared remote control. In some cases, it is desirable to extend the range of the available control and... Read more
A simple NiCd charger can be built using ‘junk box’ components and an inexpensive LM317 or 78xx voltage regulator. Using a current limiter composed of R3 and a transistor, it can charge as m... Read more
Physicians and repair engineers often use small light pens for visual examination purposes. Rugged and expensive as these pens may be, their weak point is the bulb, which is a ‘serviceable’... Read more
Did it ever occur to you that an array of white LEDs can be used as a small lamp for the living room? If not, read on. LED lamps are available ready-made, look exactly the same as standard h... Read more
Two multivibrators with different frequencies an be built using the NAND gates of a 4011 IC. If the output of IC1.B is positive with respect to IC1.C, LED D1 is on. As the levels of IC1.A an... Read more
