Trouble understanding AC motor speed regulator circuit

Discussion in 'The Projects Forum' started by shady_engineer, May 16, 2014.

  1. shady_engineer

    Thread Starter New Member

    May 16, 2014
    1
    0
    Hey Guys

    I want to build a motor speed regulator circuit and I've came across this schematic:

    [​IMG]

    Before I build it I want to understand how it works in case if I wanted to customize it. Could someone help me
    understand what the following parts of the circuit exactly do:

    [​IMG]

    Thanks in advance to anyone who answers ;)
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,548
    2,373
    They are there for (electrical) noise suppression.
    Triac controllers can throw out a lot of EMI.
    Incidentally the only brushed motor to use with that is a Universal type.
    Max.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,653
    632
    The red box is a snubber to keep the voltage across the triac from changing so fast that the triac is turned on by current through the capacitance between MT2 and the gate.

    Don't know why L1 (the green box) is there.

    The yellow box is a two pole delay network that controls the phase in the AC half cycle at which the diac fires to turn on the triac.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,548
    2,373
    The H.D. type that I have fixed or cannibalized have the choke, it is in the form of a 1" length of ferrite with two layers of #14g enameled wire.
    These are usually used for EMI suppression (high impedance to switching noise).
    Max.
     
    Last edited: May 16, 2014
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    L1 is to stop HF spike noise (from the AC mains or motor) going through C4 and turning the DIAC and TRIAC on (causing false triggering).

    Ideally the DIAC should only be turned on by the slow rise of voltage each halfcycle through the RC timing networks.
     
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