Under the new rules of the road in the sake of safety, drivers of vehicles (especially when driving outside the city) should include the day of the lights But turn them off after a stop often forget If Parking is prolonged, the battery is badly discharged In chains prevent such troubles offer a simple device, which signals that the headlights were left on while the engine is stopped, and also indicates the inclusion of the turn signal Device contains a sound generator transistors (VT1, VT2) and a threshold of the relay (K1, VD1).
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What is the kit-the fan does not dream to collect small-sized power source? But here everything depends on the power transformer: it-largely determines the dimensions of the power supply. If you try to make a transformer with a minimum size of, for example, with a magnetic core Ш12Х12, provided that the voltage of 220 V, the number of turns of the primary winding will be approximately 7600.
In most of our schools calls still include the old — fashioned way of push-button attendant or watchman. But this process is not difficult to automate. Proposed device designed for this purpose and may be made in the school radio. The block diagram of the device of the machine shown in figure 1. Electronic digital clock serves at a specified time in the actuator control signals. The actuator enables and disables the programming device, which, in turn, in accordance with the schedule of calls includes internal buzzer and external powerful school bell, feeding him the voltage is 220 V.
At first glance, the school gym is the same as thousands of others. But this is only at first glance… Observant person will note here something unusual. On boards and panels, attached to walls, installed button. Hanging above the light Board. The gym class begins with warm-up, and then the class is divided into groups. Students in one group with a small running start then jump at a time, hand hitting the button. While the scoreboard lights up every time the figure is estimation.
The Internet caught the eye diagram of the automatic charger Ni-Cd batteries developed by Yuri Bashkatov. Assembled the circuit on the breadboard — not working. Modeled it on the computer using the program Work Bench. The result is what is shown in the diagram. The device operates as follows. The transistor VT1 (p-n-p) is open if at its base there is a negative potential, which may appear when the VT2 transistor (NPN) open — this, in turn, occurs if the potential at its base is installed with the variable resistor R4 will be 0.3 — 0.4 V higher than on its emitter.
Aquarists usually determine the turbidity of the water in the aquarium, visual manner (“eye”), and beginners don’t change it until then, until it is radiating the smell. However, with the help of an electronic device, which is easy to collect a couple of free evenings, you can control the suitability of water in the tank for future use, with high precision, eliminating the notorious “human factor”. Will benefit from this approach all people and their Pets in the aquarium.
In the Arsenal of the Amateur radio voltmeter almost the most important measuring device. But the trouble is that to produce and it is not always possible. And not because the scheme is complicated. For many, the stumbling block is the arrow microammeter. However, at first it can be replaced by electron-optical indicator 6Е5С (6Е1П) or neon lamp. But first you need a high anodic voltage (up to 300V), and the second measures relicina capacity below 55 V.
If you doubt the validity of a diode, transistor or want to determine their conductivity type, use one of the devices with which we introduce you in this article. The advantage of the devices is simplicity: they can even build a new ham. The basic design is based on schematics from the Bulgarian journal “Radio television electronics”.
Sometimes the output current in the power supply can be increased up to a critical value (due to the increase of power consumption, faulty connections or load devices), which will inevitably lead to the accident consequences of overload can be significant and even irreparable if you use a power supply without the security host (like today often make hams, making simple sources and buying cheap adapters) for Example will increase power consumption, can lead to failure of network transformer, it is possible to separate fire elements and odor.