I finally built and tested my dimmer, and everything works, below is some rambling about the details.

If anyone has any suggestions/critiques I would welcome them.

I have the schematic and board layout in Eagle format as well as the C source and hex file if anyone wants them.




The project is a dimmer- more specifically a reverse phase control dimmer, using MOSFETs for switching and a PIC 16F88 for control. The PIC turns on the fets at zero-crossing and switches them off after a specified time.

The PIC can be monitored/controlled through a serial interface (RS422), and has a rudimentary command line interface. If the bulb is burned out (i.e. no load) a message is sent through the serial interface. Changing lighting levels is done smoothly at an adjustable rate, allowing bulbs to be ramped up to full power without a large rush of current at turn on.

An external switch can be monitored to override the current setting.

The design uses MOSFETs in parallel to reduce power consumption and reduce heat dissipation on the fets. Q2 and Q4 were not installed on the prototype. There was no noticeable heating when dimming 500w bulbs, so they may not be necessary for any reasonable load.

The firmware for the PIC was written in C and compiled using SourceBoost.

The prototype is currently controlling my porch light, and connected to a linux box that turns the lights on at sunset and off at sunrise. If the bulb burns out the linux box will send me an email notifying me.[img][/img]

Attached Images

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