Fading Light

Greg Lewis

I am fairly new to the basic stamp so please pardon the basic-nature of this question:

I would like to use the stamp to control a 110V AC light (2-of-them to be precise). What I would like to do is fade one on while simultaneously fading the other off. The purpose of this is to create a Pepper's Ghost effect. I have an idea (or two) but I thought I would hear what other people have done before I "poison" the well of ideas with my own. Since this is line-voltage and potentially deadly, I thought I would get help with this instead of my usual trial and error methods.

If this is a subject that has already been covered, perhaps someone could point me to a reference?

Thanks!

Greg

Jon Williams

You might want to checkout our EFX forum; the Pepper's Ghost effect has been discussed there and a couple solutions presented. While we haven't started any designs yet, the EFX team is looking into a s simple-to-control multi-channel fader.

And this posting from our Projects forum might be helpful: http://forums.parallax.com/showthread.php?p=524010

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Jon Williams
Applications Engineer, Parallax

Post Edited (Jon Williams (Parallax)) : 3/24/2006 10:56:47 PM GMT

Greg Lewis

I built a light dimmer using a triac, potentiometer and misc. other parts·(similar to what was discussed in the posting you included). I will try using the information posted. Thanks! It was well-written.

My thought was to use the PWM command and a RC-4 relay board with a Crydom solid state relay to turn the light on for a "percentage" of its operating time. Would this work? It seems too simple. There must be something I'm missing.

Thanks

Greg

Jon Williams

You cannot use a Crydom relay to dim; it will simply do on and off. Dimming requires a "smart" circuit to monitor the AC voltage zero-cross and then gate the triac at the time appropriate for the brightness level (the farther from the ZC time, the dimmer the output).

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Jon Williams
Applications Engineer, Parallax

Greg Lewis

Does a schematic (like the one I attached) exist for the the Porp-1 controller. I think it would prove useful when trying to hook-up components. I have searched but have been unable to locate it among the information at the Parallax website.
Thanks,
Greg

Jon Williams

I don't think so, but I'll check. Here's the skinny: All I/O pins are protected by 220-ohm in-line resistors that connect to the "W"·pins on the I/O header, and feed the associated input channel of the ULN2803. P6 and P7 also connect to the center pin of the 3-pin SETUP headers; the outer pins connect to Vdd and Vss through 10K (pull-up/pull-down) resistors.

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Jon Williams
Applications Engineer, Parallax