This security alarm device (SAD) is intended for automatic sounding of an alarm signal (electric bell) in case of unauthorized entry of outsiders into a protected premises — an apartment, a country house, or a garage. It features higher noise immunity and the absence of false alarms. The device is powered by a 12-volt battery Read more…
Many people keep various pets, and spending time with them brings plenty of pleasant moments to both children and adults. However, there are also animals that constantly live near humans and often visit their homes (for example, mice and rats). Yet they are uninvited and even harmful guests, since they are considered (and, probably, not Read more…
Having read in issue No. 1 of “M-K” for 1989 a description of an electronic vehicle ground cut-out, I decided to use it as a simple anti-theft device. However, when the toggle switch is replaced with a push-button (as recommended by the designer V. Arapov) or with a reed switch, a highly undesirable effect occurs: Read more…
When there is an antique samovar in the house, it would be a shame not to use it at least on special occasions. You can even avoid the hassle of lighting a fire and simply pour ready-made boiling water inside. At first, that is what I did, until I decided to equip this relic with Read more…
A compact electronic regulator that makes it possible to smoothly and over a fairly wide range to change the brightness of incandescent lamp filaments, the power of a household electric heater, or the rotational speed of an AC motor shaft can be built even by a not very experienced radio amateur. After all, the proposed Read more…
Every motorist knows how difficult it can sometimes be to start a car engine on a winter morning after a long standstill. However, a relatively simple device powered from a 220 V AC mains supply will make this task much easier. The device consists of two parts (Fig. 1): one is a mains power supply Read more…
Security systems are a rapidly developing area of modern electronics. A huge number of various circuits and designs have been published that anyone who has held a soldering iron in their hands at least a couple of times can build. For example, “electronic guards” can warn of an intruder entering a room or signal the Read more…
Explosions and fires caused by gas leaks are, unfortunately, not uncommon. While giving due credit to the work of administrative bodies and emergency services, radio amateur designers can also do something themselves to minimize this danger. However, in the field of gas monitoring there are almost no simple, reproducible devices, or they are unreasonably expensive. Read more…
It is hard for an outsider to understand anglers who sit all day, as if hypnotized, with a fishing rod, never taking their eyes off the float. Of course, patience eventually runs out even for the most devoted, especially if the fish does not often reward them with bites. That is why many experiment, trying Read more…
When I needed a megaphone, I looked at the prices of industrial Chinese products: as it turned out, they cost from $45 to $235, and I decided that I could assemble a similar device with my own hands in a couple of hours. A megaphone (or loudspeaker), the electrical circuit of which I recommend and Read more…
