PWM to DC +/_ 10 volts

Discussion in 'The Projects Forum' started by paulepc, Apr 2, 2014.

  1. paulepc

    Thread Starter Member

    Apr 2, 2014
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    I am trying to convert a pwm signal from a JR radio control receiver to plus/minus 10 volt to drive a motion controller. the input to the controller has 120K ohms impedance. 12 bit sampling frequency 2 kHz

    My curent setup is wire from the receiver channel to a R-C low pass filter, and feeding that into a NE5534AP op amp.
    the R-C filter seems to look ok on the scope although the voltage drops from about 3.5 to .5 volts.

    I have been days trying to solve this problem. Can someone give me some guidance please. I have a very basic knowledge of electronics.

    Thanks
     
    Last edited: Apr 2, 2014
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    This may be a start.
    Max.
     
  3. paulepc

    Thread Starter Member

    Apr 2, 2014
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    Thanks for the reply.
    Is this for generating a PWM, as I have already got the PWM coming from the receiver.

    Paul
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    PWM to analogue conversion.
    Max.
     
  5. paulepc

    Thread Starter Member

    Apr 2, 2014
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    I just looked at the data sheet, it looks really complicated, My goal is to drive 10 axis bruges servo motors wirelessly I have 2 axis working so far but hard wired. So decided to look into wireless control.
    I'll do some reading on the chip to see if I can get my head around it.
    Paul
     
  6. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    There was no chip in the PDF, only a way on page two to calculate the lowpass filter. What is your PWM clock frequency, and can you post your schematic?

    ak
     
  7. paulepc

    Thread Starter Member

    Apr 2, 2014
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    On my calculation it is either 22 or 44 kHz
     
  8. paulepc

    Thread Starter Member

    Apr 2, 2014
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    Sorry forgot to put the schematic
     
  9. paulepc

    Thread Starter Member

    Apr 2, 2014
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    Can anyone help out here?
    Paul
     
  10. abhaymv

    Active Member

    Aug 6, 2011
    104
    4
    Not sure if this will help, but this is what I'd do:

    Feed the PWM (I assume 0-5V) to an op amp configured as a level detector. Configure the level to be detected as 2.5 V. This should give you a +/- 10 V output if you adjust the supply voltages to the op amp.
     
  11. paulepc

    Thread Starter Member

    Apr 2, 2014
    55
    0
    Thank you. I think there will be a waveform coming out of the op amp do you use a rc low pass filter?

    Do you have a schematic you could share?

    Paul
     
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