PWM with variable duty cycle on a chip? 
Author Message
 PWM with variable duty cycle on a chip?

Hi,

I am working on a project with a data acqusition board.  I need the
ability to send an analog voltage to a device (or devices) and be able
to adjust the duty cycle of a PWM voltage from about 25% to 100%.

I tried using a 555 timer, but it is somewhat unstable.  Does anyone
know of a device which will perform this function, or have any other
methods to try?

thanks,

-avery



Sun, 24 Sep 2000 03:00:00 GMT
 PWM with variable duty cycle on a chip?

Hi Avery,

Take a look at http://www.ionet.net/~bschwabe/BasicStampll/v2pwm.gif.
Hope this helps.

Good Luck
James Page

Quote:

> Hi,

> I am working on a project with a data acqusition board.  I need the
> ability to send an analog voltage to a device (or devices) and be able
> to adjust the duty cycle of a PWM voltage from about 25% to 100%.

> I tried using a 555 timer, but it is somewhat unstable.  Does anyone
> know of a device which will perform this function, or have any other
> methods to try?

> thanks,

> -avery



Sun, 24 Sep 2000 03:00:00 GMT
 PWM with variable duty cycle on a chip?

Quote:

>Hi,

>I am working on a project with a data acqusition board.  I need the
>ability to send an analog voltage to a device (or devices) and be able
>to adjust the duty cycle of a PWM voltage from about 25% to 100%.

>I tried using a 555 timer, but it is somewhat unstable.  Does anyone
>know of a device which will perform this function, or have any other
>methods to try?

>thanks,

>-avery

After searching myself for a Voltage to PWM converter on a single IC,
that provided a 0% to 100% duty cycle adjustment and a BASE-FREQUENCY
greater than 25kHz with absolutely no luck (Hard part was the
BASE-FREQUENCY).  The only thing I found even close from LINEAR
TECHNOLOGIES was a variable speed cordless drill driver with a
BASE-FREQUENCY of 5kHz.

  I designed my own that will go from 0% to 100% with an input voltage
ranging from 0V to 5V and provides a BASE-FREQUENCY of about 31kHz on a
single IC.  (Dual OP-Amp)

http://www.ionet.net/~bschwabe/BasicStampII/0000.html

http://www.ionet.net/~bschwabe/BasicStampII/v2pwm.gif

...There is also another version that I have that will operate down to
2.5V (BF=34kHz)that I haven't posted yet.  If you are working with 3V
logic I can provide it to you.  The above method (v2pwm.gif) fails to
oscillate at about 4.5V supply voltage.



Mon, 25 Sep 2000 03:00:00 GMT
 PWM with variable duty cycle on a chip?

Quote:


> >Hi,

> >I am working on a project with a data acqusition board.  I need the
> >ability to send an analog voltage to a device (or devices) and be able
> >to adjust the duty cycle of a PWM voltage from about 25% to 100%.

> >I tried using a 555 timer, but it is somewhat unstable.  Does anyone
> >know of a device which will perform this function, or have any other
> >methods to try?

> >thanks,

> >-avery

Try a regulating PWM IC, like a SG3524. Feed your analog input to the
compartor input (pin 9)  Carrier freq is determined by a resistor and a cap.


Mon, 25 Sep 2000 03:00:00 GMT
 PWM with variable duty cycle on a chip?

Harris make a 8pin SPI driven Digital PWM - cdp68hc68w1 - check their web
site

Tony D.
Newcastle, UK



Thu, 28 Sep 2000 03:00:00 GMT
 
 [ 5 post ] 

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