AN1003
Application Notes
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+1 972-580-7777
AN1003 - 8
2002 Teccor Electronics
Thyristor Product Catalog
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 microcontol-
ler 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.
120 V ac
(High)
AC
(Return)
White
RV
Varistor
R
1
47
C
0.1 μF
+5 V
R
2
1 M
D
1N4001
D
1N4001
R
20 M
D
1N5231
C
220 μF
C
0.01 μF
V
DD
GP
5
GP
4
GP
3
V
SS
GP
0
GP
1
GP
2
R
6
470
Q
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