Improved Triac circuit

* Theoretical analysis: up to 6:14min
* Practical analysis with oscilloscope: 6:14 to 13:09.

In this video, we discuss how the phase shift between the input voltage and the timing capacitor introduces a hysteresis when the circuit operates at high phase angles (lowest dimming settings). This can cause flickering as the phase angle timing may be wrong or missed. In addition, when the dimmer is started, a 'pop' effect is often seen, where the circuit does not start until the phase angle is reduced and then increased again, for example where a bulb brightness must first be increased at turn on, before it can be reduced to the lowest settings.

The circuit comprises a method to remove any residual charge from the timing capacitor at each zero crossing, so as to give the circuit an accurate starting time base, at every phase angle of operation

The Video covers the detailed explanation of the circuit, together with a practical overview of the produced waveforms, including a comparison between the generic circuit and the new improved version.

[carmelpule]

This is an excellent circuit, The Diodes seem to cater for the peak of the 120 Volt supply and 600 Volts is being extra safe.
The capacitor C! at 7:42 is shown as an electrolytic but this C1 has to accept both polarities.
A good idea and it provides a great improvement to the unit.

[vincentrobinette]

The real problem comes, is this circuit is used to control the speed of a shaded pole induction motor, or, a transformer for low voltage halogen lighting. If there is any asymmetry whatsoever between the negative and positive half-cycles, it can introduce a DC bias, which can cause magnetic core saturation. At that point, a transformer acts as though the secondary is short-circuited, and the impedance drops to the DC resistance of its primary winding. The smoke comes quickly! I'm wondering if this corrects DC bias? My solution in the past, is simply to install a very large value electrolytic capacitor in series with the phase controller, and let it charge up to the offset voltage, eliminating any DC current to the load. The motor in my humidifier now runs much cooler, and makes much less humming noise, because of removing ~3 volts of DC bias, caused by triggering offset.
I have a soldering station that uses this circuit, to control the wattage dissipated by the iron itself. and its offset can range from 1 volt to almost 9 volts, depending on the duty cycle setting. Fine, because the heating element is just a resistance, but if I want to use this to drive any kind of inductive load, it's an absolute no-go. at very low settings, it actually only triggers half wave. This might be a perfect candidate for the resistor/bridge rectifier test! (I AM going to "try this at home"!!) GREAT VIDEO.. thank you for posting. I learned a lot.

[kattaylor]

Although not explicitly indicated with a + sign, the capacitor symbol shown is typical of a polarized capacitor.

[tommymorton]

Where can I see the final schema?
Also can it be adopted for 230V mains?

[alilatifovic]

Electrolytic cap charged to -20v ? On your pcb can't see the c1 (electrolytic one)

[drewhalliday]

Does it matter where you put the load?