Thyristor Semiconductor Products Page 36 Thyristor

2014 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 12/14/14 Teccor brand Thyristors AN1003 120 V ac (High) AC (Return) White RV 1 Varistor R 1 47 C 3 0.1 F +5 V R 2 1 M D 1 1N4001 D 1 1N4001 R 3 20 M D 3 1N5231 C 1 220 F C 2 0.01 F V DD GP 5 GP 4 GP 3 V SS GP 0 GP 1 GP 2 R 6 470 Q 1 L4008L5 R 4 470 R 5 470 S 2 S 1 Bright Dim V DD 150 W Lamp JP1 Remote Switch Connector 1 2 3 U1 12C508 Figure AN1003.23 Microcontroller Light Dimmer Control With a zero crossing state detected, software can be written to turn on the Triac by going from tri-state to a logic high on the gate and be synchronized with the AC phase cycles (Quadrants I and IV). Using pull-down switches connected to the microcontoller inputs, the user can signal the software to adjust the duty cycle of the Triac. For higher amperage loads, a small 0.8 A, TO-92 Triac (operating in Quadrants I and IV) can be used to drive a 25 A alternistor Triac (operating in Quadrants I and III) as shown in the heater control illustration in Figure AN1003.24. For a complete listing of the software used to control this circuit, see the Microchip application note PICREF-4. This application note can be downloaded from Microchip's Web site at www.microchip.com. Phase Control Using Thyristors (continued)

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