By including a variable resistor in series with the capacitor in the above circuit, frequency can be varied along with the duty ratio. As this resistor is involved in both charging and disch... Read more
If you look at the chassis of the zBot vehi-cle, you’ll find two parts requiring intel-ligent control: the steering servo and the DC motor. The so called H-bridge is the normal circuit... Read more
Control by sound may be very useful, not just on a robot but also for a bit of home automation, for example, a sound-activated light responding to a knock on the door or a hand clap. The lig... Read more
Most PC enclosures provide only a single LED to indicate hard disk access, with the LED being connected to the motherboard via a two-pin connector. However, this LED only works with IDE driv... Read more
It is not generally known that it is possible to ascertain the extent of charge of a battery with a standard digital voltmeter. It does not apply to all kinds of battery, but it does to, for... Read more
An LED is sure to fail if the current through it is too high. You will soon discover this after you have blown a few up. A simple resistor in series suffices to solve the problem and a bette... Read more
Märklin’s light signal Type 74391 (blocking signal) for size HO model railway sets is fairly new and, at 10 euros (£7·00), reasonably affordable. There is, however, a little problem in that... Read more
The circuit described here is mostly aimed at development engineers who are looking for an economical step-down converter which offers a wide input voltage range. As a rule this type of circ... Read more
The LR12 made by Supertex Inc. is a good choice for applications where a supply voltage of more than 35 to 40 V needs to be stabilised. This small regulator can cope with input voltages of u... Read more
After buying a number of DECT telephones, we noticed that these became quite warm while charging. That surprised us, because the manufacturer wrote in the manual that the batteries had to be... Read more
