[moved] how to convert pwm to 0-10v output

[PRIYADHARSHINI PALANISAMY]

Hi all
I want to convert the PWM signal 0.8v - 4.5v to 0 to 10v .here i have attached my schematic .it gives
10V output for 0.8V
and 10V output for 4.5V ..

 

[KlausST]

Re: how to convert pwm to 0-10v output

Hi,

i´d prefer R2 to 10k for better PWM frequency attenuation.
for even better attenuation connect a 1uF across R3

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With PWM 0.8 - 4.5V you mean Low and High level?
With 0..10V you mean analog voltge?

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You didn´t say this, but you want to reverse output? Instead 10V...0V you want 0V...10V?

if so: then you have two ggod options.
1) either you make the second stage non inverting (bu you need a negative voltage for offset correction
2) or you make the first stage inverting.

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Btw: the 0.8 and 4.5 depend on supply voltage. If you don´t want this, then use an anlog switch. Switching between 0V and 10V for example. Then you don´t even nedd the OPAMPs.


Klaus

 

[PRIYADHARSHINI PALANISAMY]

Re: how to convert pwm to 0-10v output

Thanks for your reply Klaus.
my PWM input is continously varying one.
If i make first stage as inverting..the output of first stage should be -0.8v....then output of second stage will be
(vin + - vin -)*gain
(i.e) (-0.8-0.8)*2.7=4.32 v..but i need 0v for 0.8v.

and any other option to eliminate the 0.8v supply at second stage of opamp???
how can i add a offset to an opamp?

 

[Audioguru]

Re: how to convert pwm to 0-10v output

You forgot to tell us the PWM frequency so we can see if the input filter works.
If the filter works then when the DC input to the first opamp is +0.8V then the output of the second opamp should be close to 0V.
When the DC input tor the first opamp is +4.5V then the output of the second opamp should be close to +11.16V.

 

[KlausST]

Re: how to convert pwm to 0-10v output

Hi,

there are countless solutions.

one is:
first stage inverting. Gain -1, In+ = 2.25V (converts 0.8 ... 4.5V to 3.7V ...0V)
second stage inverting: gain -10/3.7; In+ = 2.70V (converts 3.7V ... 0V to 0V ... 10V)

Mind that the LM324 is not a Rail to Rail output one.

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For further discussion please give informations requested in post 2 and 4

Klaus