DC motor rpms control

Discussion in 'The Projects Forum' started by white_michael, Jun 19, 2012.

  1. white_michael

    Thread Starter New Member

    Jun 19, 2012
    Hi, all
    I`m now designing a dc motor controller for turntable.
    I decided to use tachometer feedback and apply LM2917 frequency-to-voltage converter. In application notes I got three circuits: first circuit gives something like PWM and is not suitable for turntable.
    Second gives proportional regulation, but it has "poor load regulation".
    About third circuit I know only that it employs IC acting like shunt mode regulator.
    So can you tell me what does mean here "poor load regulation" and which circuit (2,3) will be more suitable for turntable rpms controller? (My turntable is Polish UNITRA G-602)
    Here is a link to app.notes:
    Thanks in advance,
    and sorry for my English
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    "Poor load regulation" means with load (drag) on the motor the speed will drop badly. You need good load regulation I think.

    Did you know you can buy DC motors for tape and turntable use that have a very good speed regulation circuit already built into the end of the motor? Most good turntables with DC motors have this type of motor and all you do is connect DC power and the motor will run at an exact speed. These type of motors can be bought from anywhere that sells spare parts for tape and turntable repairs. They usually have a small trimpot in the end of the motor for speed adjustment.
    Last edited: Jun 19, 2012