Analogue to PWM signal converter

Discussion in 'The Projects Forum' started by fjulianelli, Jul 5, 2013.

  1. fjulianelli

    Thread Starter New Member

    Jul 5, 2013
    2
    0
    Hello all,

    I'm working on a project and I'm facing a problem on my next task. I need to convert the analogue output of a dual pot device to a PWM signal to be read by an other device. Both signals voltage are 5v and the PWM frequency is 250±20 Hz.
    ANALOGUE SIGNAL ----> (ANALOG to PWM CONVERTER DEVICE) ----> PWM SIGNAL

    Does anybody knows witch microcontroller could I use to build this converter?

    Thanks in advance!
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    What is the nature of your signal? I mean, do you want a voltage-to-duty cycle converter? Do you have a schematic?
     
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  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,978
    744
    It can be done with a dual 555 (556) by varying the dc voltage on the control pin(11) this alters the 1/3 to 2/3 reference thresholds, and controls the speed of the pwm pulses,

    or you could use an LM331
     
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  4. fjulianelli

    Thread Starter New Member

    Jul 5, 2013
    2
    0
    Wayneh and Dodgydave, thanks for your reply!
    Attached here are the source analog signal graphic and the expected PWM signal graphic.
    Both signals are 5v DC.

    Best Regards.
     
    Last edited: Jul 5, 2013
  5. donpetru

    Active Member

    Nov 14, 2008
    186
    25
    You have to make an application with a microcontroller so that you can better control the variation of input-output circuit measurements. But to do this you have to precisely calculate input-output transfer function. Then you can make application with a simple microcontroller like: Attiny25, 45 or 85 (choose attiny85 because it has more flash and the price is the same ~~ 1$).
    If you can not handle, ask and I'll help you.
     
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  6. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,039
    287
    At such a low frequency, you can do this with a few op amps. First generate a 50 % duty cycle square wave. (a 555 timer will work fine. Run this through an integrator to obtain a triangle wave. Combine the triangle wave and the MODULATING analog signal in a simple adder. Take the output of the adder and apply it to a COMPARATOR The output of the comparator will be a PWM signal. This is how some A.M. broadcast transmitters have done this for a couple of decades. :)

    Eric
     
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  7. donpetru

    Active Member

    Nov 14, 2008
    186
    25
    Even if he chooses analog circuit solution or choose the solution with microcontroller, in both cases must be drawn input-output transfer function (to get a better result).
    The disadvantage of analog solution (example, with operational amplifiers) is that: after calculating the transfer function should be explored poles component values ​​function to correct small non-linearity function that will undoubtedly exist. This operation involves many components bonding and delaminate to find more accurate solution, when all this can be replaced by more modern optimization software.
    It's his choice, but think carefully.
     
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