In SX Microcontrollers, SX/B Compiler and SX-Key Tool, InSilico wrote: [color=black>Yay!] [/color] Anyway, since the christmas holidays will be coming (time flies by quick), I've decided to take on a more "advanced" projects using the SX microcontroller, namely light dimming for christmas lights! I've worked with high voltage stuff before (namely my house electrical system :-) ) so I know what to do when it comes to safety. One must have a healthy respect for electricity, especially ones at mains voltages. It might be an interesting project, to integrate the world of low-voltage digital circuits and high-voltage AC systems. The "Dimming the Lights Fantastic" Nuts & Volts article is my inspiration for the project (which is very well written, along with the other N&V articles). Since I'm way too lazy to search through the million different items on Mouser, I have already placed an order for the MOC3023 optoisolated triac drivers and H11AA1 optoisolated AC input, as well as the triac. However, I have added my own "enhancements" to the basic dimmer circuit. One of which is EMI/RFI reduction by a 0.047 uF capacitor and an 100 uH inductor (designed for mains voltages/currents), with the inductor connected between the triac and the load and a capacitor in parallel with the triac (see attached picture). No, I did not come up with these values in thin air, [url=http://www.epanorama.net/documents/lights/lightdimmer.html]http://www.epanorama.net/documents/lights/lightdimmer.html[/url] suggested using these values. Another is the use of fuses and a "master" relay which can act as a software-controlled kill switch which cuts off power to the dimmer circuit when needed. Also, I'll put in a neon lamp indicator to indicate the presence of mains voltages. On the microcontroller side, I'll add an EEPROM to store dimmer sequences and add a primitive user interface to "flip" through sequences. Direct control via RS-232 to the computer is possible. I already made my own C++ program that will communicate/download sequences to the controller. The SX program that performs the phase control will be written in assembly (already got serial comms, EEPROM read/write, etc. down). I will put the circuit on a custom made PCB (I got the chemicals and "practiced" with them already). Each "part" will be put on it's own "miniboard", and then connected together. A modular approach, so I can fix individual dimmers if they need be. I'll also design a WARNING! label to tell people that the high voltages should not be messed with :p . Now the questions start: I've decided a maximum of 10A which figures to a 1.2 kW capacity (more than enough for a domestic light application), while individual channels will be fused for 4A (of course adding up all the channels exceeds 10A, but that's okay). That means the PCB traces might need to handle up to 10A of current (or 4A for the individual dimmer modules). How wide should the traces be? I get different answers everywhere I look. BTW, I'll be using 1 oz./sq. ft. copper clad board. How hot will the traces get to be? Or should I just solder 18AWG wire directly to the pins on the bottom on the board (a la protoboard) just to err on the side of caution? Is 39k ohm appropriate for connecting in series with an indicator sized neon light? I heard somewhere this is a good value for 120V operation? Is the circuit sound? Or is there a blaring mistake that needs to be fixed right away? Less serious mistakes? Much appreciated! P.S. Sorry for the incredibly long post. I need to provide some context. P.P.S. Pic of schematic + parts list attached. The schematic included the SX Microcontroller schematics, but I've omitted that for brevity. ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=288652 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2008 (http://www.dotNetBB.com)