Looking for circuit plan for 100V / 0-15W dimmer

Discussion in 'Power Electronics' started by dschmitt, Aug 1, 2016.

  1. dschmitt

    Thread Starter New Member

    Aug 1, 2016
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    I need help designing a circuit board for a 100V / 0-15W dimmer with a turning knob. My plan is to put this circuit board into a small box with the input coming from a 100V power wall outlet and the output connected to a 100V fan. Within the fan the 100V power goes directly into a coil. The coil is rated at 15W.

    I took an electronics class as an undergraduate, have played a lot with my sons SnapCircuit kit and have experience sodding various very simple circuits. I know the basics but a dimmer is above my knowledge, even though I realize that a dimmer is also very basic. I cannot draw the circuit but I think I will understand it when I see it. I live in Tokyo near Akihabara. Therefore based on the circuit plan I can buy all the parts and build it.

    Please somebody help out and draw a circuit plan for a 100V 0-15W dimmer and specify clearly the individual parts.
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
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  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Depending on the type of motor in the fan, its speed may not be fully controllable with a dimmer circuit.
     
  4. #12

    Expert

    Nov 30, 2010
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    A quick check of the intergoogle tells me Tokyo has 100 VAC RMS at 50 Hz.
    There are millions of AC dimmers available for low prices but I tried this and found that the fan would not run at any drive setting below 70%.
     
  5. dschmitt

    Thread Starter New Member

    Aug 1, 2016
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    I considered a plugin dimmer like the one in the below Amazon link
    https://www.amazon.com/Lutron-TT-300H-WH-Electronics-Plug-Dimmer/dp/B0000BYEF6

    The description says 300W. I have seen similar devices in local electronic stores. They were also in the 200-300W range. I am afraid if I buy one of these 90% of the range of the dimmer has no effect on the fan motor speed because its range is up to 15W. That is the reason why I am now considering to make a dimmer by myself.

    The below link opens a webpage I created with a picture that shows the fan motor. It is a coil/motor combination. The fan has a slow and fast setting. The slow is 13W and the fast is 15W. Each speed circuit has its own cable connecting to the coil (yellow and red). White is shared.
    http://detlefschmitt.main.jp/Fan_motor/Fan_Motor.html

    Perhaps I should check in Akihabara whether somebody sells dimmer knobs of various watt ranges. Maybe I find one that is my range or close to my range.

    But then it is likely that I also run in the "does not run below 70% setting" problem. Hard to tell. If I find a dimmer knob for a few hundred yen then I give it a try.
     
  6. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    No, it doesn't work like that. The dimmer works by restricting the fraction of the mains cycle which gets through to the load. So at the 50% setting your 15W load would draw 7.5W, whereas a 300W load would draw 150W.

    That motor is of a type known as a shaded pole motor and should respond reasonably to dimmer type circuits. The problem might be that the dimmer may not like the inductive load of the motor which may upset its proper functioning.

    ETA: The following is from the questions on that item on the Amazon site:
    "It says it's not intended for motor loads or other non-lighting loads."
     
    Last edited: Aug 2, 2016
  7. dschmitt

    Thread Starter New Member

    Aug 1, 2016
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    I see. I didn't know that. Also thanks for the hint about the potential problem.
    So, I guess I will be looking then for a 100V dimmer which can handle motor loads.
     
  8. dschmitt

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    Aug 1, 2016
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  9. AlbertHall

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  10. dschmitt

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    Aug 1, 2016
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    I see. I understand. With a capacitor in parallel a light dimmer that normally handles resistive loads can be made usable for an inductive load motor. So much about the theory. I think I will try first if I cannot get a ready made fan dimmer with minimum speed adjustment. If not, then I will give it a try. Question in that case would be: what type capacitor would I need?
     
  11. AlbertHall

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    Jun 4, 2014
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    The capacitor should be X rated, generally X2 - suitable for connection across the mains supply - and rated for an AC voltage greater than your supply, perhaps 150V. Here we have 230V mains and I would use one of those capacitors rated at 275V.

    The value is anybody's guess though...
     
  12. dschmitt

    Thread Starter New Member

    Aug 1, 2016
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  13. dschmitt

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    Aug 1, 2016
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    what would happen if I am way off with the C-value?
     
  14. AlbertHall

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    Jun 4, 2014
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    The capacitor is connected correctly.
    If the capacitor is very large it might damage the dimmer but I don't know how big very large is!
    Do you have any way of measuring the inductance of the motor?
     
  15. dschmitt

    Thread Starter New Member

    Aug 1, 2016
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  16. dschmitt

    Thread Starter New Member

    Aug 1, 2016
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    would a SCR Constant Voltage AC Motor Speed Controller work?
    See example on Amazon here.
     
  17. AlbertHall

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    Looks good to me.
     
  18. dschmitt

    Thread Starter New Member

    Aug 1, 2016
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    thanks for letting me know. I will check in Akihabara whether somebody sell such a device.
    I can't believe this $7 piece is sold for $40 at Amazon Japan.
     
  19. takao21203

    Distinguished Member

    Apr 28, 2012
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    Because theres artificial scarcity for electrical parts in Japan.

    The circuit is similar to attached. The MAC97A6 for instance is a low power TRIAC and costs a few cents (though its not possible to do a sale for a few cents these days).
     
  20. dschmitt

    Thread Starter New Member

    Aug 1, 2016
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    thanks for the drawing of the TRIAC. I read about it but don't exactly understand how it works. With your simple drawing I should be able to figure it out. About Japan. Import products that are not otherwise available in Japan are often incredible expensive on Amazon. The price is probably a combination of exclusivity, import tax, very low volume and shipping cost. Anyway, whatever the reason, I should not buy the 110-220V item for a 100V fan. And in Akihabara I should be able to get a motor dimmer. Akihabara has an area where individual electronic parts are sold like resistors, capacitors, volt converters, etc. I should be able to find there what I need, now that I know what I am looking for.
     
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