Rongge

The operation of the dimmer is based on phase control; during a full cycle of an AC waveform, a thyristor will only allow a part of the waveform to be delivered to the load. Take a look at the following waveforms:   The only difference is that the waveform on the left will bright the lamp higher than the waveform on the right. That is because, on the left waveform, the triac will be conductive earlier than the triac shown in the right waveform.  The time that the triac becomes conductive is symbolized with the Greek letter α (ALPHA) , called firing angle, so controlling this angle you can control the phase voltage, and is measured in angles from the zero point of the waveform. This zero point is the point that the voltage is 0 volts, and this happens 2 times every one full period of the wave form. When the α becomes smaller, then the dimmer becomes conductive sooner and the lamp is brighter. When the α becomes bigger, then the triac delays more to become conductive and thus th...

If you’ve ever tried dimming a LED with a simple potentiometer, you know that the approach does not work very well. Just as with ordinary diodes, the voltage-current characteristic of LEDs is far from linear. The result - depending on the potentiometer setting the LED brightness will hardly change most of the time as the pot is turned and a sudden variation at the end. The best method to tackle this problem is to power the LED from a current source with zero to 100% adjustment range. The circuit shown here is an example. A low-current LED (D1) is used to generate a reference voltage that’s first buffered by one half of an LM358. The actual current source that powers the LED(s) is built around the second opamp in the chip. Circuit diagram: 30-mA LED Dimmer Circuit Diagram The potentiometer allows the output current to be adjusted, with R2 acting as a current sense, the resistor dropping the same voltage as the one obtained from the pot. Using Ohm’s law we find that the maximum current t...

Here is simple electronic circuit Project of phase-controlled dimmer circuit. A phase-controlled dimmer delays the triac turn-on to a selected point in each successive ac half cycle. Phase-Controlled Dimmer Circuit Diagram:   Use this circuit only for incandescent lamps, heaters, soldering irons,or universal motors that have brushes.

This is a very simple circuit of a dimmer, ie a controller LED brightness, which is powered from the USB port of a PC and a connection is very simple. The resistor R1 sets the maximum current of the LED with the maximum potentiometer, resistor R2 should have a resistance of 10x to 100x greater than R1. The table shows which components to use in accordance with the selected LED. Dimmer-Brightness LED Driver Circuit Diagram

This handy circuit can be used as a speed controller for a 12V motor rated up to 5A (continuous) or as a dimmer for a 12V halogen or standard incandescent lamp rated up to 50W. It varies the power to the load (motor or lamp) using pulse width modulation (PWM) at a pulse frequency of around 220Hz.  SILICON CHIP has produced a number of DC speed controllers over the years, the most recent being our high-power 24V 40A design featured in the March & April 2008 issues. Another very popular design is our 12V/24V 20A design featured in the June 1997 issue and we have also featured a number of reversible 12V designs.   Project Image :  12V Speed Controller/Dimmer Project Image For many applications though, most of these designs are over-kill and a much simpler circuit will suffice. Which is why we are presenting this basic design which uses a 7555 timer IC, a Mosfet and not much else. Being a simple design, it does not monitor motor back-EMF to provide improved speed regula...