Phase Control Using Thyristors - Littelfuse
Phase Control Using Thyristors - Littelfuse
Phase Control Using Thyristors - Littelfuse
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AN1003<br />
Application Notes<br />
120 V ac<br />
(High)<br />
R 1<br />
47<br />
C 3<br />
0.1 µF<br />
D 1<br />
1N4001<br />
V DD<br />
AC<br />
(Return)<br />
White<br />
RV 1<br />
Varistor<br />
150 W<br />
Lamp<br />
+5 V<br />
R 2<br />
1 M D 1<br />
1N4001<br />
V DD<br />
U1<br />
V SS<br />
D 3<br />
1N5231<br />
C 1<br />
220 µF<br />
C 2<br />
0.01 µF<br />
R 3<br />
20 M<br />
GP 5<br />
GP 0<br />
Q 1<br />
L4008L5<br />
GP 4<br />
GP 3<br />
GP 1<br />
R 6<br />
470<br />
GP 2<br />
Remote<br />
Switch<br />
Connector<br />
JP1<br />
Dim<br />
S 1<br />
12C508<br />
R 4<br />
470<br />
3<br />
2<br />
Bright<br />
S 2<br />
R 5<br />
470<br />
1<br />
Figure AN1003.23<br />
Microcontroller Light Dimmer <strong>Control</strong><br />
With a zero crossing state detected, software can be written to<br />
turn on the triac by going from tri-state to a logic high on the gate<br />
and be synchronized with the AC phase cycles (Quadrants I<br />
and IV). <strong>Using</strong> pull-down switches connected to the microcontoller<br />
inputs, the user can signal the software to adjust the duty<br />
cycle of the triac.<br />
For higher amperage loads, a small 0.8 A, TO-92 triac (operating<br />
in Quadrants I and IV) can be used to drive a 25 A alternistor<br />
triac (operating in Quadrants I and III) as shown in the heater<br />
control illustration in Figure AN1003.24.<br />
For a complete listing of the software used to control this circuit,<br />
see the Microchip application note PICREF-4. This application<br />
note can be downloaded from Microchip's Web site at<br />
www.microchip.com.<br />
http://www.teccor.com AN1003 - 8 ©2002 Teccor Electronics<br />
+1 972-580-7777 Thyristor Product Catalog
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