Generally zero crossing triac drivers are not recommended for motor control. A motor presents a load that is partially inductive. This introduces a phase shift between the applied voltage and the current through the motor. This phase shift can cause problems with zero crossing detectors when you want to turn the triac off. If the load were purely inductive, the voltage would cross zero when the current was at the peak. (a purely inductive load causes the current to "lag" the applied voltage by 90 degrees, assuming sinusoidal voltage). Triac circuits for inductive loads generally require "snubbers" to limit the rate of rise of voltage across the triac when they try to turn off. With an inductive load the current always starts at zero. You can apply the peak of line voltage to an inductor and the current will be zero at the instant of application of the voltage. Some types of motors present a high current demand at turn-on, NOT because they are inductive loads, as many people will claim, but because they are ... motors. A motor acts as a generator, producing a voltage that is counter to the voltage that makes it spin (this is "back EMF"). At stall (startup) that voltage is zero, so the current is mostly a function of inductive reactance and winding resistance. As the motor spins up the magnitude of the back EMF increases and the current drops. High current typically lasts for many AC power cycles. Some motors require very little more current at startup than when running. Zero crossing triac triggers are good for bang-bang control of things like heating elements because it can ease the radio frequency interference mitigation requirements. You would never use a zero crossing trigger where phase angle control dimming is desired. It is exactly what you don't want to do. You need to be able to turn the current on part way through each half cycle of AC and the zero crossing detector actively prevents that. An exception would be a more sophisticated dimmer that turns on at zero crossing and off part way through each cycle, which requires active ("forced") commutation if you are using triacs or SCRs. This again is done to reduce EMI/RFI. It is pretty much unknown in consumer dimmers because of the complexity. If you want smooth dimming of AC operated lamps using a microcontroller you need to make a circuit that tells the micro when the line voltage crosses zero, start your timer at the end of zero crossing and fire the triacs after a delay. If you can find them on the web, I recommend some old Motorola ap notes on opto triac triggers. Mota was the first company to make such, many years ago. There is also a very old General Electric SCR/Triac handbook that is excellent (but does assume you know lots of basic electricity and electronics).
Just an additional safety note. Please try and have any IC chip that has high energy going through it facing away from yourself. I had a DIP 8 switch mode controller IC explode on me when I had accidentally shorted some of it's pins with a solder splash and I was lucky that the board was upside down as a chunk of the chip exploded off when I applied power. Really glad that did not hit me in the face.
Yes, I failed to mention that I had put on some safety glasses because, even though I didn't really think there was a possibility of the thing actually exploding, I didn't wanna take any chances.
@@brainwater As long as your glasses are rated to be safety glasses that is fine. But for the most part standard glasses are not safety rated and will actually cause more damage if they shatter from an impact. There is a Project Farm demo where they compare proper safety glasses to standard sun glasses (which are similar to standard glasses) and they do not do very well. I also ware standard glasses and have had a blob of molten solder fly from a metal tab that was spring loaded that I was soldering to a battery and go under my glasses and barely miss my eye. I would recommend wearing the sealed safety glasses if possible to prevent such things from happening.
Generally zero crossing triac drivers are not recommended for motor control.
A motor presents a load that is partially inductive. This introduces a phase shift between the applied voltage and the current through the motor. This phase shift can cause problems with zero crossing detectors when you want to turn the triac off. If the load were purely inductive, the voltage would cross zero when the current was at the peak. (a purely inductive load causes the current to "lag" the applied voltage by 90 degrees, assuming sinusoidal voltage). Triac circuits for inductive loads generally require "snubbers" to limit the rate of rise of voltage across the triac when they try to turn off.
With an inductive load the current always starts at zero. You can apply the peak of line voltage to an inductor and the current will be zero at the instant of application of the voltage. Some types of motors present a high current demand at turn-on, NOT because they are inductive loads, as many people will claim, but because they are ... motors. A motor acts as a generator, producing a voltage that is counter to the voltage that makes it spin (this is "back EMF"). At stall (startup) that voltage is zero, so the current is mostly a function of inductive reactance and winding resistance. As the motor spins up the magnitude of the back EMF increases and the current drops. High current typically lasts for many AC power cycles. Some motors require very little more current at startup than when running.
Zero crossing triac triggers are good for bang-bang control of things like heating elements because it can ease the radio frequency interference mitigation requirements.
You would never use a zero crossing trigger where phase angle control dimming is desired. It is exactly what you don't want to do. You need to be able to turn the current on part way through each half cycle of AC and the zero crossing detector actively prevents that.
An exception would be a more sophisticated dimmer that turns on at zero crossing and off part way through each cycle, which requires active ("forced") commutation if you are using triacs or SCRs. This again is done to reduce EMI/RFI. It is pretty much unknown in consumer dimmers because of the complexity.
If you want smooth dimming of AC operated lamps using a microcontroller you need to make a circuit that tells the micro when the line voltage crosses zero, start your timer at the end of zero crossing and fire the triacs after a delay.
If you can find them on the web, I recommend some old Motorola ap notes on opto triac triggers. Mota was the first company to make such, many years ago. There is also a very old General Electric SCR/Triac handbook that is excellent (but does assume you know lots of basic electricity and electronics).
Just an additional safety note. Please try and have any IC chip that has high energy going through it facing away from yourself. I had a DIP 8 switch mode controller IC explode on me when I had accidentally shorted some of it's pins with a solder splash and I was lucky that the board was upside down as a chunk of the chip exploded off when I applied power. Really glad that did not hit me in the face.
Yes, I failed to mention that I had put on some safety glasses because, even though I didn't really think there was a possibility of the thing actually exploding, I didn't wanna take any chances.
One advantage of needing corrective glasses is i never have to remember to put on safety glasses.
@@brainwater As long as your glasses are rated to be safety glasses that is fine. But for the most part standard glasses are not safety rated and will actually cause more damage if they shatter from an impact. There is a Project Farm demo where they compare proper safety glasses to standard sun glasses (which are similar to standard glasses) and they do not do very well. I also ware standard glasses and have had a blob of molten solder fly from a metal tab that was spring loaded that I was soldering to a battery and go under my glasses and barely miss my eye. I would recommend wearing the sealed safety glasses if possible to prevent such things from happening.
Nem tiveram o trabalho de colocar legenda , afinal falo portugues e nao ingles , nao sou gringo.