Pic Dem Dimmer 12C508

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INTRODUCTION

PICREF-4
This combination of familiar and new features in a compact package gives the designer unprecedented flexibility to produce designs which are much cheaper and smaller than ever before possible, and allows the replacement of even mundane devices like timers and discrete components economically. This reference note describes an application where the use of amicrocontroller was not previously economically feasible for any but the highest end products: lamp dimming.

PICDIM Lamp Dimmer for the PIC12C508

The PIC12CXXX family of devices adds a new twist to the 8-bit microcontroller market by introducing for the first time fully functional microcontrollers in an eight pin package. These parts are not stripped down versions of their larger brethren, they addfeatures in a package smaller than available ever before for microcontrollers. Using the familiar 12-bit opcode width of the PIC16C5X family with the same TMR0 module, Device Reset Timer, and WatchDog Timer (WDT), the PIC12C5XX family adds an internal 4MHz oscillator main clock, serial programming, wake-up on change, user selectable weak pullups, and multiplexing of the MCLR, T0CKI, OSC1, and OSC2 pins.Information contained in this publication is intended through suggestion only and may be superseded by updates. No representation or warranty is given and no liability is assumed by Microchip Technology Inc. with respect to the accuracy or use of such information, or infringement of patents arising from such use or otherwise. It is the responsibility of each user to ensure that each UPS isadequately designed, safe, and compatible with all conditions encountered during its use. “Typical” parameters can and do vary in different applications. All operating parameters, including “Typicals”, must be validated for each customer application by the customer's technical experts. Use of Microchip's products as critical components in life support systems is not authorized except with expresswritten approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights.

© 1997 Microchip Technology Inc.

DS40171A-page 1

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TABLE OF CONTENTS
Hardware overview ......................................................................................................................................3 Software overview.......................................................................................................................................5 Design Modifications ....................................................................................................................................5 APPENDIX A: SYSTEM SPECIFICATIONS .......................................................................................9APPENDIX B: BILL OF MATERIALS...................................................................................................9 APPENDIX C: SOFTWARE PROGRAM ...........................................................................................11 APPENDIX D: DIM508.LST FILE ......................................................................................................17

ACKNOWLEDGMENTSProject Lead Engineer:
Scott Fink

System and Code Development:
Scott Fink

DS40171A-page 2

© 1997 Microchip Technology Inc.

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HARDWARE OVERVIEW
Lamp dimming using a TRIAC
Logic level TRIACS are a relatively new introduction. They allow a microcontroller to directly drive (through a current limiting resistor) the gate of a TRIAC. TRIACs can be used to control the brightnessof a lamp by switching the AC power on part-way through each half wave (Figure 2 and Figure 3). By controlling where the TRIAC is "fired" during the power-line cycle, the microcontroller can control the average voltage across the filament of the lamp, and thus the brightness. The TRIAC used for this application is able to handle lamps up to a maximum of 100W. R9 is connected to the "hot" lead of...