hair dryer circuit diagram

Discussion in 'General Electronics Chat' started by zargarpour, Mar 21, 2015.

  1. zargarpour

    Thread Starter New Member

    Mar 21, 2015
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    Hi,


    Request for help: Does anyone know how to wire a hair dryer components (4 wire heather, motor and its bridge rectifier (4 diodes – 1N 4004 ) and 3 electrical switches.

    Any help would be greatly appreciated. Thanks.
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Welcome to AAC
    Quite simple.
    One problem. Need to know the resistance of the heater as there will be low heat and high heat adjustments.
    You need to measure the resistance of the wires so we can figure out the correct way to wire the switch.

    Need to resistance from wire to wire. All the wires of the heater
     
  3. ian field

    Distinguished Member

    Oct 27, 2012
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    All the ones I've seen had the motor "enclosed" by the bridge rectifier - or in correct terms, the motor is across the + & - terminals.

    The heater is in series with the bridge AC terminals, so the current through the heater also passes through the motor - but is rectified.

    Most of the ones I've seen, the power level switch switches a power diode in or out of series with the mains, chopping off half the half-cycles reduces the power.
     
    Roderick Young likes this.
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I somehow feels that this part may be wrong.
     
  5. Roderick Young

    Member

    Feb 22, 2015
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    EDIT: I stand corrected. See following posts...

    I agree with Ian Field. If it's a cheap travel dryer that runs of either 120 or 240, then there's a DC motor inside, which will run off a wide range of RMS voltage. The mode switch has 2 poles and 2 throws. One pole of the switch controls whether half-wave or full-wave rectified voltage is applied to the motor, giving high or low speed.

    I believe that the heater DOES go to the AC terminals, as Ian says. It makes no sense to burden the rectifiers with the heater power. The other pole of the mode switch is used to route AC mains power either to across the whole element (higher resistance, LOW setting), or to a center tap on the element that puts the two halves of the element in parallel (much lower resistance, HIGH heat setting).

    The switch on the dryer that sets it to 240 volts does nothing except block the mode switch from being on HIGH. When you set the dryer to 240 volts and plug it into 240 volts, the switch is always set on LOW, but the dryer blows fast and hot air as if it was set on HIGH on 120 volts.
     
    Last edited: Mar 22, 2015
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    Actually, the heater current does pass through the bridge rectifier - the heater basically acts as a dropper resistor for the motor.

    The motor in those things is almost always about 12V, a mains voltage universal, brushes motor that small would be prohibitively expensive, so its either use the heater as a dropper resistor or include a step down transformer - again more cost, and the weight would make it uncomfortable to hold.
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Isn't it also likely that the dryer will also include some kind of thermal fuse or cutout?

    I didn't see one in the components list.
     
  8. zargarpour

    Thread Starter New Member

    Mar 21, 2015
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    The heater element has a SEKI ST-12 bimetal thermal cut-out switch (connected to Red wire) for overheat protection set at 120 degree. Also, a power diode (1N 5408) is connected to the blue wire of heater.
     
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  9. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Now he tells us,

    So is there anything else?
     
  10. zargarpour

    Thread Starter New Member

    Mar 21, 2015
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    just need a diagram assembly on how to wire these items together.
     
  11. zargarpour

    Thread Starter New Member

    Mar 21, 2015
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    resistance of wires in the heater element is as follows:-

    1) black with red is 96 ohm
    2) black with blue is 220v 187w
    3) black and brown both with red is 48 ohm
    4) red with blue can't connect
    5) red with brown is 96 ohm
    6) blue with brown is 220v 187w
     
  12. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    How did you figure this ?
     
  13. zargarpour

    Thread Starter New Member

    Mar 21, 2015
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    Asked from manufacturer of element.
     
  14. ian field

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    Oct 27, 2012
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    They usually have a bi-metal strip in the hot airflow - also a one-shot thermal fuse is pretty common.
     
  15. RichardO

    Well-Known Member

    May 4, 2013
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    For a while I was using a cheap hair dryer for heating heat shrink tubing. I found that the dryer was not hot enough unless I blocked some of the airflow. :D
    This worked unless I did it too long -- then the thermal switch would trip and I would have to wait for it to cool down before I could proceed. I was luck that it was not a thermal fuse.
     
  16. ian field

    Distinguished Member

    Oct 27, 2012
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    Used to be possible to get jet flame cigarette lighters - but they're banned because junkies like them for coocking up smack in tinfoil.

    A regular lighter will do heatshrink, but leaves a lot of soot.
     
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