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Fader/Dimmer for AC Lights — Parallax Forums

Fader/Dimmer for AC Lights

skipperskipper Posts: 2
edited 2005-11-29 19:11 in BASIC Stamp
I'm trying to control 2 sets of ac light strands in a Christmas display with alternating dimming/fading capability. One set brightens and holds on·for a predetermined time while the second set dims and holds off.·The second set then brightens while the first set dims.
Anyone know of an archived project with schematics and code for a BS2e that would help me?
Thanks.

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-11-23 21:22
    Have you seen this?: http://forums.parallax.com/showthread.php?p=524010

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    Jon Williams
    Applications Engineer, Parallax
  • metron9metron9 Posts: 1,100
    edited 2005-11-27 20:29
    After reading the linked post, i thought it would be fun to try doing the same thing only using a 12V AC powersupply, the kind used for outdoor lighting. I am using a Malibu 88 watt maximum.

    Question, Instead of using the H11AA1 I wanted to experiment using what I had on hand, a 4N28 Linkto datasheet: http://www.fairchildsemi.com/ds/4N/4N28.pdf

    I do try and figure out what the minimum and maximum voltages/currents that devices have but I just don't see what the current and voltage rating on input side of this device is rated at. Using the values in the authors schematic for the zero crossing optocoupl

    Is the following math correct.

    150 Volts peak flowing through two 15k resistors would give about 5mA of current (150/30,000)
    This doesn't seem enough current as I know LED's especially infrareds take much more but I don't know how much current it takes to trigger the device.

    1. From the datasheet how did the author calculate that 15k resistors were needed for the H11AA1 device :Link to datasheet[noparse]:http:[/noparse]//www.fairchildsemi.com/ds/H1/H11AA1.pdf

    Would two 1.2k resistors work (for my 12VAC system) using the 4N28, and I realize it only has one LED so it wont give both from high to low and low to high crossings, actually I dont really know what it will do but I suspect just the low to high crossing would be what I could get and I would divide by 2 to estimate the high to low crossing after the first two crossings came in.

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    Think outside the BOX!
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2005-11-27 23:35
    Well, metron9 --·stay·inside·the box.

    · A 4N28 is a opto-transistor not an opto-triac.· Opto-transistors switch·DC voltages.·

    · "Zero-crossing" refers to the triggering of the triac, when AC crosses zero volts -- as opposed to "random triggerring", where it would occur most anywhere in the cycle, so to say.· Zero-crossing is much quieter so far as EMI emisssions are concerned.

    · Here's an excellent·Application Note from Littelfuse all about·these matters:

    www.littelfuse.com/data/en/Application_Notes/AN1007.pdf

    · Don't go to burning down the house.

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  • metron9metron9 Posts: 1,100
    edited 2005-11-28 02:06
    Ahh yes but PJ, I am not talking about the opto-triac part MOC301 0M, and I not using 110 volts I am using 12 Volts AC

    My thought was to use a Diode 1N400x and a 2 resistor voltage divider to trigger the opto-transistor (4N28) to give a high low signal on a stamp pin.
    So I would be switching a DC 5V through the transistor of the opto, but driving the opto with a DC signal pulse by using the diode/resistor divider.

    I would expect the on time and off time of the logic pin on the stamp to trail the actual 12Vsine wave but it should be consistant in that respect so a delay in turning on or off the drive circuit.

    Actually after thinking about it some more, I may just fully rectify the AC to DC and PWM the DC voltage through a MOSFET using the 4N28 on the logic side to drive the MOSFET.

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    12VACDiode.JPG
    640 x 480 - 61K
  • skipperskipper Posts: 2
    edited 2005-11-29 18:30
    Jon,

    Thanks for the post last week. Been out of circulation for a few days.

    I looked at the post you suggested, but would like to do this with a minimal amount of curcuit construction.

    Was thinking there may be a way to use a couple of X-10 control modules driven by a BS-2E through a PL-513. Do you know where I might find the code to accomplish the brightening/dimming routine using that configuration?
  • Bruce BatesBruce Bates Posts: 3,045
    edited 2005-11-29 19:11
    skipper -

    The Stamp BS-2 series is capable of sending the necessary X-10 codes you require, via the XOUT command which is well documented in both the PBASIC Help File and the PBASIC Manual. You could output those commands to either a PL-513 (uni-directional) or TW-523 (bi-directonal) X-10 Interface Unit.

    There are simple examples in both places noted above, which should be enough to get you started on your way.

    Regards,

    Bruce Bates

    Post Edited (Bruce Bates) : 11/29/2005 7:24:44 PM GMT
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