Readers who do not care to modify the power supply of an old PC into a suitable halogen power source (see our April 2006 issue), may find the present design a welcome alternative. The circuit does not need any changes to the power supply. It allows the halogen lamps to be initially powered from the 5V rail of the supply via RE2, so that they are p
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reheated. Subsequently, they are powered from the 12-V rail via RE1, while at the same time the 5-V rail is disconnected. This ensures that the current surge through the lamps is so small that the protection in the power supply does not react. Operation of the circuit is as follows. As soon as the PC supply provides power, IC1. B drives T1 into conduction and RE2 closes. The potential at the non-inverting input of IC1. B is 6 V, while that at the inverting input rises from 0 V. Lamp LA1 is then connected to the 5-V rail. After a short span of time, the voltage across C1 has risen to a value where IC1. B changes over, whereupon T1 is cut off. At the same time, IC1. A drives T2 into conduction. The circuit is then decoupled from the 5-V rail and connected to the 12-V terminal. The 5-V rail in the PC power supply is protected against spikes on the 12-V line by D1. Diode D2 protects IC1 against over-voltage on its inputs should the 12-V rail fail. Resistors R4 and R5 limit the base currents of the transistors. D3 and D4 are quenching diodes. The time during which lamp LA1 is powered by 5 V is preset with potentiometer P1. The maximum time span is about 0. 33 s and the minimum 3. 3 ms. The latter is perhaps rather short, but it also depends to some extent on the type of power supply used. Some experimentation may be worthwhile!
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
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The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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