Triac Dimmer - convert 220V to 110V circuit?

Discussion in 'The Projects Forum' started by mvmacd, Jul 23, 2015.

  1. mvmacd

    Thread Starter New Member

    Jan 5, 2015
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    Hi, I owned some DIAC (DB3) and TRIACs (Q4003L3), and set up a simple circuit.
    I can't seem to find the Q4003L3 datasheet, but looked up "equivalent" and red that datasheet to get the pinout.

    It's similar to this schematic on ebay:
    [​IMG]

    with the exception of the LED and D1, I just have a wire instead.

    Now, the thing is I only have 1K and 10K potentiometers, and I just ordered ten 500K potentiometers tonight on eBay. What I am having trouble with is finding the correct value of capacitor in order to have full range. I guess I shouldn't have ordered so many, since the 220V schematic calls for the 500K, and it's 120V here in the USA.

    In the picture, the capacitor is labeled ".1/50" and I totally don't understand that. (It can't be 0.1uF @ 50V I don't think? because it needs to be at least 200V/400V) Please see the eBay item and tell me what you think.

    I had 224K and 473K green capacitors in my spare parts bin. with 224K, the 10K pot doesn't change the wattage of the load, but with the 473K it limits the upper end (about 50W Max, 40W min if I remember right). Oh, I'm using a window fan btw. They don't mind having the sine wave chopped off, right? I did test it for about 10 minutes with a commercial 1000W resistive load dimmer, and the motors did not get hot at all.

    So can someone tell me which value of capacitor I need? (To compliment my 500K potentiometers. Or should I have bought a different value?)
    Also, what do they call those green-ish capacitors, so I know what to search for?
     
  2. mvmacd

    Thread Starter New Member

    Jan 5, 2015
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    bump
     
  3. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The L4003L3 can not be found.
    The L4004L3 can be found in the attached booklet, on page 22 (E1-2).

    Bertus
     
  4. mvmacd

    Thread Starter New Member

    Jan 5, 2015
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    I looked, but I don't understand how to calculate the capacitance value. Can you help?
     
  5. bertus

    Administrator

    Apr 5, 2008
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  6. ian field

    Distinguished Member

    Oct 27, 2012
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    A triac phase control isn't going to convert 220V to 110V!!!

    When the triac is triggered, its volt drop is about a volt only - most of the 220V will appear across the load.

    The control is effected by the fact that the current isn't flowing 100% of the time.
     
  7. mvmacd

    Thread Starter New Member

    Jan 5, 2015
    26
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    Sorry I wasn't very clear in the title. What I mean was, the circuit is meant for 220V, but I want to use it on a 110V and calculate the capacitor.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
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    Calculation won't be straight forward because the diac breakover voltage will be a greater proportion of the available charging voltage.

    Try half the capacitance and see where you end up, you could probably alter the resistor to trim any remaining error.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Did you test it on 120v to see the range you have?
    Max.
     
  10. mvmacd

    Thread Starter New Member

    Jan 5, 2015
    26
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    Yes, I did. see my original post:

    I had 224K and 473K green capacitors in my spare parts bin. with 224K, the 10K pot doesn't change the wattage of the load, but with the 473K it limits the upper end (about 50W Max, 40W min if I remember right).

    Oh, and the K doesn't stand for K-Ohm, I don't think, I think it's the tolerance of the capacitor. The 473 capacitor only let me change 50W [full] to 40W, and that was turned all the way down [most resistance?] on the 10K pot. (
     
  11. absf

    Senior Member

    Dec 29, 2010
    1,492
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    Did you try Google Images for "triac dimmer schematics for 120V"? I found a few which may be helpful to you ...

    AAC dimmer 1.jpg AAC dimmer 2.jpg AAC dimmer 3.jpg
    Allen
     
  12. mvmacd

    Thread Starter New Member

    Jan 5, 2015
    26
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    Yeah, I have searched a lot in the past. But I don't have all those value of capacitor and pots.

    That's why I started this thread to see if anyone knows how to calculate the capacitance in relation to the resistance (pot), but apparently nobody knows how.

    So thanks everyone. I guess I will just pull random values from old circuit boards (have a few old PSU from old PCs) and try it when my potentiometers arrive, until I get one with good range (if I find it I'll post it)
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,542
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    According to my old 1979 GE Triac/SCR engineering manual, in a simple Pot, Cap, Diac, Triac circuit for either 120v or 240v they show the difference in potentiometer value only.
    250k for 120v 500k for 240v, in series with the 0.1μf Capacitor.
    Max.
     
    absf likes this.
  14. mvmacd

    Thread Starter New Member

    Jan 5, 2015
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    Thanks. That helps! I'll start with that value (or the closest I have) and go from there. Still waiting for the mail though for my potentiometers.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    224k is 0.22uF, 473k is 0.047uF. Use two of the 473k caps in parallel to get roughly 0.094uF
     
    Last edited: Jul 30, 2015
  16. DickCappels

    Moderator

    Aug 21, 2008
    2,651
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    mvmcd wrote:
    "In the picture, the capacitor is labeled ".1/50" and I totally don't understand that. (It can't be 0.1uF @ 50V I don't think? because it needs to be at least 200V/400V) Please see the eBay item and tell me what you think."

    By now you should have confirmed that .1/50 is in microfarads. As for the voltage rating of the capacitor -20% or more above the Diac threhsold voltage should be fine because the Diac limits the maximum voltage across it.
     
    absf likes this.
  17. mvmacd

    Thread Starter New Member

    Jan 5, 2015
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    Now I feel pretty dumb!
    In the picture, the capacitor did not look like one of the 50V types (looked like the 200V or maybe 250V). But thanks, I do appreciate it because I can use cheap 50V capacitors.
     
  18. DickCappels

    Moderator

    Aug 21, 2008
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    Hey, don't feel bad. I was using high voltage capacitors in this circuit too until I realized where the capacitors are in the circuit.
     
  19. mvmacd

    Thread Starter New Member

    Jan 5, 2015
    26
    7
    Could you also tell me if putting too large a capacitor would burn the pot? I accidentally a 10K pot. I put in a capacitor that I couldn't fully read the code. Maybe it was really big?

    But no have more 10k in the mail! (eBay is the best)

    Also, I plan to use multiple triacs in paralell to make a boiler heat control. (1000W) would this split up the l load? I don't have any 1000W triacs, I think the ones I have are 3A-5A, But can't find exact datasheet so I'm not sure.
     
  20. mvmacd

    Thread Starter New Member

    Jan 5, 2015
    26
    7
    Just wanted to post an update: with 500K pot, and the original schematic (minus the led and diode), a 0.047 uF capacitor (573 code) works pretty well to give a full range, rated for 50V. (I used a 25V cap and it got busted) However, I ended up going with a lower value because since the control isn't linear, I wanted more precise control over the top 3/4ths. (I think I used 223 + 103 capacitor together)

    Fan controller works great. [​IMG]
     
    ebeowulf17 and DickCappels like this.
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