It often happens when someone from the household forgets to turn the lights off in the toilet — he may be there without the use of a lot of hours. A simple automatic device which, when necessary, turns on the light in the bathroom, and when not — turn off. The electrical circuit of such device is presented in figure 1. It contains: a low-power transformer T1, rectifier VD1 — VD4, filter capacitor C1, two limit switches SB1 and SB2 relay K1. How the device works and how it performs its functions?SAVE YOUR TIME
When painting window frames faced with the need to protect glass so as to remove dried paint is difficult and time-consuming — it takes a lot of time. Apply on the glass a thin layer of rubber glue and glue strips of paper around the edges. After the paint dries a bit, remove the paper Read more…
I’m a physics teacher and a faithful subscriber of the journal “modelist-Konstruktor”. Write and assemble a binder began while still a student in 1980. Thanks to him I became one of those whom the people called “avid homebrew”. One of my first designs was a mini-tractor “Gerez”, built together with the guys from the circle of technical creativity, which was led by part-time. Mini tractor took first place in the Republican review of technical creativity of pupils. Engine — motorized С3Д installed across; the gearbox from the car GAZ — 51, rear axle — from “UAZ”, shortened. At the mini-tractor 20 gears: 16 forward and 4 backward speed from 1 to 52 km/h. Its own mass of 500 kg can pull the truck with load up to 1200 kg.
The smaller the cubic capacity of the engine performance, the more stringent the requirements for its design, manufacture, Assembly. Speed, cord of 1.5 cm3, which we offer, fine-tuned for many years, takes into account the shortcomings of previous designs and new directions in creating “polutorachasovom”.
It is used in teaching music in rhythmic gymnastics, in experiments in physics etc. a Metronome, a scheme which offers Bulgarian journal “Radio Television Electronics” (see Fig.), gives not only audio but also visual signals. With the help of variable resistors R1, R2 their frequency change in the range of 40 to 200 cycles / min. which corresponds to the musical pace from “grave” to “Prestissimo”.
This model has for many years successfully “replicated” by the modelers. The secret of its popularity are the simplicity of design and good flight qualities. And despite the immutability of the size of the “serial” model, in various instances were established micro-motors a working volume of from 2.5 to 4 cm3 in the compression and glow options. But the most often used are widely known for KMD-2,5 and equipped with a propeller diameter 220×120 mm Length of cord, generally used for runs close to the standard value of -16 meters. For the manufacture of parts of the model mainly applies to non-deficient materials.
