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Author Topic: AC Light Dimming  (Read 9225 times)
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Just posted a really crappy video (I need a new camera).  It shows the Ac wave on the scope, some light blinking, and a bit of fading.  
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Hi All, I'm trying to get Ryan's circuit to work, and I have the zero cross detection functioning (yay!). Anyway, regardless of the arduino being even plugged in, the lights stay on. I'm sure I've read the schematic wrong, because it seems to me that the output circuit is shorted across R8 and the capacitor (CX1). So regardless of whether the triac is open or closed, the AC goes right through. Any insight would be great, I'm sure it's simply that I don't know how to read the schematic. Thanks All!
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Ok, so I didn't even know how a capacitor worked, hadn't read that section in the book yet. But I still don't understand. A capacitor will block DC current (eventually) but will let AC current through, no? So in this case because we have AC, it should go right through the capacitor regardless of the state of the triac, no?
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Got it to work by pulling out the capacitor… anyone know what it's there for?
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attached a slightly updated schematic.  The block with the AC_Out is
your load (a light for example).  On my board I have this as a hot and
neutral to connect the load.

I am trying to remember what the capacitor is used for.  It will make
a difference in the performance of the circuit when dimming.  Check
out the MOC3020 data sheet for more info and some other schematics.
It also should be a cap rated for 250V.  Part of that circuit is the
feedback to OK2 to ensure the triac fires properly.

Hope this helps.

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Glad to see there is so much progress on this topic!  This is getting far more detailed than I ever expected. Awesome!

Sorry I have not been around too much.  My "real" job has been keeping me away from fun projects like this.  However, I have been having some more time lately to get back into things.

I should be posting in the next few days some more info on the final version of the "Darwin Shield"   smiley-grin  4 AC I/O for the Arduino.  I am trying to work out the best way of enclosing the whole thing and connectors for each output.  Let me know if you have any input.
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I did a project very similar to this a few years ago. I skipped putting in protections for inductive loads while I was developing the circuit. Worked great on lights and such. Then I forgot I had skipped the inductive load protection and plugged in a dremel. Worked great for about 20 seconds.   :smiley

Thanks for posting details.
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I actually ended up getting it to work with the capacitor. Mind explaining what inductive load protection is? Is that what the capacitor is for?
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Quote
attached a slightly updated schematic.  The block with the AC_Out is
your load (a light for example).  On my board I have this as a hot and
neutral to connect the load.

Sorry, but shouldn't you use a bridge rectifier inbetween the AC input and your opto-isolator? Or is it unnecessary?

« Last Edit: August 19, 2009, 08:46:17 am by ritzdank » Logged

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The H11AA1 actually has 2 diodes between pins 1 and 2, one facing each direction, so you don't need a rectifier if you use that IC. The 4N25M only has one diode, so you need to use a rectifier with that chip.
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Has anyone actually tried using this example to dim multiple lights? I am wondering how to implement the timing issues with switching more than one pin on the arduino where each one has a different value for 'dim'. Anyone have any success or sample code they'd like to share?
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Has anyone actually tried using this example to dim multiple lights? I am wondering how to implement the timing issues with switching more than one pin on the arduino where each one has a different value for 'dim'. Anyone have any success or sample code they'd like to share?

Hi,

I did it here:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1251810521

Sorry, but it's in French...

With this code, you can drive 8 lights, probably more. Each light is independent: you can change the 'dim' value via the IDE serial monitor by sending a frame like

           " D/0/45/F"
     => a space
     => "D" = start of frame flag
     => "/" first separator
     => n° of dim channel (0 to 7)
     => "/" second separator
     => dim level (0% to 100%)
     => "/" last separator
     => "F" = end of frame flag

In the last version of code, I have added a transition delay when you change 'dim' value. This delay should be modify.

If you are interessing by the last version of the code, perhaps I can translate the comments and publish here ?

Gromain
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Thanks Gromain,
I think I can manage the translation, however I think you have only uploaded the initialization part of the code in that thread. The second half of the code appears to be missing.
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Chicken,

Sorry, I've just upload the second part of code now !!
After the first post, I was unabled to post again ("internal server error" ?!).
This morning it's ok.
If you have any question/improvement/feed-back, please contact me.
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I've been reading this post for awhile now.  I made a single output dimmer.
Recently, I translated the french code Gromain put up.
I then made a multi (3) output triac circuit.
My lights are flickering.
I assume it has something to do with my 60Hz 120v
and you have 50Hz 220v?
What do i have to change to make the flicker go away?
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