Tachomotor

Discussion in 'General Electronics Chat' started by DexterMccoy, Apr 17, 2014.

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  1. DexterMccoy

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    Feb 19, 2014
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    A Tachomotor uses a servo amplifier with a speed processor

    The speed processor circuit get a differential input and outputs a inphase or out of phase voltage to the servo amplifier

    My question is what causes or controls the tachomotor speed?
    1.) is it the phase degree?
    2.) Is it the amplitude?
    3.) Is it the differential voltage?

    The larger the differential voltage , the faster the tachomotor speed is?
    The small the differential voltage , the slower the tachomoter speed is?
     
  2. MaxHeadRoom

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    A tachometer does not use a servo amplifier, it is the reverse.
    Are you talking DC tach or digital tach?
    In the case of a DC tach, the DC out is proportional to the motor rpm.
    This tach output is summed with the command signal to arrive a the required set RPM in order to limit the rpm to the commanded set point.
    This is called a velocity loop.
    Max.
     
  3. DexterMccoy

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    Feb 19, 2014
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    So what does it use?

    what is the amplifier called to drive the tachometer?

    DC tach, it has a motor coil and a generator coil

    Proportional to what? an input differential voltage?

    What circuit is this called that does this?

    Is this the processor speed circuit?
     
  4. MaxHeadRoom

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    The amplifier does NOT drive the tach, the tach is an INPUT to the drive, it is typically summed with the ±10vdc analogue input signal (OP amp summing amplifier).
    The tachometer is rarely if ever used on modern servo's now due to the drive loop being a transconductance type amplifier in nature (torque mode).
    i.e. Motor current proportional to the analogue voltage input.
    The older tach input drive was called a velocity amplifier.
    Max.
     
  5. DexterMccoy

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    How can a tach be an input, when it's a motor coil?

    So what drives the tacho motor?

    The Velocity amplifier , was a amplifier that drives the tachomotor

    The Velocity is a differential voltage and voltage phase that drives the tachomotor
     
  6. MaxHeadRoom

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    You are obviously in possession of some information that I have hitherto never heard of, or come across so it is pointless for me to go on.:rolleyes:
    Max.
     
  7. BillB3857

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  8. DexterMccoy

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    so what is the circuits that work with the tachometer called? the circuits that control the tachometers speed and direction?
     
  9. BillB3857

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    Did you even take the time to read post #4? What did it tell you? Did you look at the link I spoon fed to you? What does the bold type at the top of it say?
     
  10. debe

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    Sep 21, 2010
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    Interesting post Bill sounds a bit like this circuit from a Furuno2000 radar antenna that I have.
     
  11. BillB3857

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    Neat post, Daryl, BUT, please don't confuse Dexter any more than he already is. Your system uses an AC tach and all the magic is handled in the LB1601. Dexter is having a hard enough time just trying to understand what a tach does, let alone the fact that there may be more than one type in use. I'm sure that after seeing your drawing he will be flooding the forum with questions about the HD FLASH signal and WHY would it be there, what is it used for and what does HD mean. BTW, Dexter works in avionics, according to statements he has made in previous posts. Autopilot drawings have been seen many times accompanied by WHY questions.
     
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  12. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    What exactly do you think a tachometer IS?
    As far as I know it is a device that measures rate of rotation, in revolutions per second.

    So it is the rotating shaft that controls the speed and direction of the tachometer input.

    That is, unless you are talking about something completely different, like the dial found in analog display type tachometers.
     
  13. ScottWang

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    Aug 23, 2012
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    You can treat a tachometer like as a low frequency counter, it will more easier to let you get into the conception, for a tachometer speed is used minute, so if you using a counter to count a period of time, assuming that the value of counter is 180 cnt, and the total time is 3 seconds, now you got the cnt = 180, t = 3S (seconds), and then the rpm = 180*(60S/3S) = 3600 rpm.

    You can figure out how a uC to work for Tachometer first, talking about what you know after reading this section.
     
  14. MaxHeadRoom

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    The majority used in DC servo applications were/are DC tachometers, a simple brushed generator.
    Max.
     
  15. ScottWang

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    You mean like this.
     
  16. MaxHeadRoom

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    Yes, I picked up a quantity of those on ebay a while ago, all brand new in the box.
    Max.
     
  17. shortbus

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    Which begs the question, why is this not a violation of the TOS, and automotive is?
     
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  18. DexterMccoy

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    Feb 19, 2014
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    Here is the Schematics for the Tachometer

    What I'm confused about is how is the Tachometer a feedback loop or in a loop?

    When the AC input signal has a differential voltage or an error voltage, it takes a Time Period for the Tachometer to MATCH the input differential voltage

    What is causing this TIME Period delay?

    You can use a stop watch and it takes 26 seconds for the Tachometer to catch up to the Input signals differential voltage
     
    Last edited: Apr 18, 2014
  19. spinnaker

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    Looks like another aircraft instrumentation schematic to me. If not most likely proprietary. Will you ever learn Dexter?
     
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  20. DexterMccoy

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    Why do you assume its an aircraft

    So all tachometer schematics are only aircraft schematics?
     
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