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Yet Another Soft Start Circuit
Yet Another Soft Start Circuit
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Old Today, 01:11 PM   #121
Mark Johnson is offline Mark Johnson  United States
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Yet Another Soft Start Circuit
Hi @tauro0221, thank you very much for the diagram in #104. It occurs to me that the hardware/software which sets the triac firing time (thus the phase angle), can be prototyped, tested, debugged, and validated using a low voltage AC sinewave. Perhaps such as the output of a mains-to-12.6VAC stepdown transformer. Now you can connect meters and scope probes and even fingertips to the apparatus, without high voltage danger. You can also attach an earth ground, which is a safe and handy reference for the test gear.

After everything is working beautifully and producing the exact oscilloscope displays you desire, only then do you install the (proven!) circuitry into a PCB which uses the live AC mains. Very nice.
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Old Today, 02:40 PM   #122
tauro0221 is offline tauro0221  United States
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Normally used a small wall AC transformer to feed the Arduino and also use it to get the zero crossing pulses to fire the traic. You need a full rectifier to get the pulses for the neg/pos side of the AC. I fired the traic on both pos/neg of the zero crossing of the AC to get smooth voltage at the secondary. Also if you do no want to use the transformer option you can get an opto coupler to get the zero crossing pulses no matter if your input AC voltage it is 120/220 AC volts. The one you can us it is the H11AA1 it will give you a pulse in the neg/pos of the AC. It is a simple concept to eliminate inrush current. Maybe people do not see the concept that what you doing it is slowly controlling the incoming voltage from a low to high voltage feeding the primary and at the same time you controlling the secondary output voltage. It is like you use an auto transformer to vary the input voltage of a transformer. The schematic it is in the #26 of this thread. Like I said before been using this concept for almost 6 years with no problems. Also you can control the voltage ramp by triggering the triac few times at the same angle of the AC.
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