Installations with restricted access are often protected using an access code. If you don’t have particularly demanding requirements regarding modifying the code, you can manage quite nicely... Read more
Mechanical contacts have the disadvantage that they wear out. That is why it is practical to use an electronic ‘touch switch’ in some situations. With such a touch switch the resistance of t... Read more
There are only a limited number of switching regulators designed to generate neg-ative output voltages. In many cases, it’s thus necessary to use a switching regulator that was actually desi... Read more
Sometimes you have to do it the hard way, even if doing it an easy way is an option. That is the case here. The intention is to add a second doorbell in parallel with the existing bell. This... Read more
It features at least once in every Small Circuits collection: the 555 timer. In this simple circuit we give the chip a little more attention than usual (refer to ‘The Eternal 555’ in the Jul... Read more
For a few pounds, you can buy a kit from any automotive accessory shop that will allow your car to be fitted with a central locking door system. Such a kit essentially comprises a number of... Read more
In order to connect the open-collector output of a standard Conrad DCF receiver module (order number 121177), which has a relatively low operating voltage of 1.5–15 V and an NPN open-collect... Read more
Electrical appliances accidentally left on in (holiday) homes left unoccupied for a short or a long period consume power unnecessarily and can present a fire hazard. Everyone will be familia... Read more
This circuit uses two comparators that are combined in what is called a window comparator, i.e. resistors R2, R5, and R10 determine a voltage window within which the voltage applied to the j... Read more
The object of this circuit turns the domestic lighting on and off in complete safety in a room with very high humidity. A detector, flush-mounted into the wall, detects the magnetic field va... Read more
