The diac is a common component used to trigger triacs. The construction of a diac is similar to that with a transistor, but with both junctions doped to similar levels so that the two junctions' revers break down characteristics are similar. This is a fun project to demonstrate the use of a pair of bipolar transistors operating in their negative resistance region to simulate a diac triggering a triac in an incandescent lamp dimmer. The circuit is not optimized for performance -it is only intended to demonstrate the principle.
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The waveforms above should look like the last 90 degrees of the positive and negative half cycles of the AC line, but this is what the hot AC line actually looks like in my neighborhood. No wonder some jurisdictions require appliances to meet power factor requirements. By the way, be careful to consider your scope probe's voltage rating when probing the AC mains, even through an isolation transformer, since the peak voltage may be higher than the probe or scope's rated voltage. I used a X100 probe rated at 1kV.
I'm not going to spend much space on this because this is not a beginners' project and the operation of this kind of lamp dimmer is covered elsewhere on the web.
The photograph above shows the voltage across an incandescent light bulb that is being driven by the triac dimmer circuit. Notice that the lamp is only being driven 1/2 the time of each half of the power line cycle. That means that the lamp only gets half the average power. The fraction of each power line half cycle applied to the lamp is determined by the time within the half cycle that the triac, which switches the voltage across the lamp, turns on. When the voltage goes to zero, the triac turns off and waits for the next trigger pulse. That's how this kind of dimmer works. But varying the phase within each half cycle at which the triac turns on.
Within each half cycle, the power line voltage charges the .068 uf capacitor through the 250K pot....
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....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
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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