IVP wrote:
> could I have suggestions for controlling an LM317 please
>
> In the attached diagram, the 10k pot is used to set the voltage
> of the HV PWM outputs
>
> What I need to add is a modulation control, which simulates
> the pot being rotated left and right. The pot will stay, modulation
> is just another mode

Instead of modulating the high side voltage of the PWM, how about folding
that into the duty cycle so that you can always run with a fixed high
voltage, 33.5V in your case?  Instead of linearly dropping half that, for
example, in the LM317, reduce the duty cycle by half instead.

How will these PWM signals be used?  What are they driving?  Is the ultimat=
e
load only going to "see" the average value?  If so, then all modulation can
be combined into a duty cycle value.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.