Homebrew PCBs

I you an op amp, some circuit I found on the 'Net. Seems to work pretty good, but doesn't have variable frequency. I would be interested in seeing your circuit.

--- In Homebrew_PCBs@yahoogroups.com, "awakephd" <a_wake@...> wrote:
>
> Richard, what kind of circuit do you have in mind for the PWM? If you're wanting to do something with discrete ICs rather than a microprocessor, I put together a PWM controller that allows for variable frequency as well as variable pulse width (true PWM) -- and it only requires 2 op-amps or comparators, so it can be made with a single chip (not counting the drive circuitry). This may be a common design -- I may have re-invented the wheel! -- but I couldn't find anything like this when I was needing this circuit. I specifically wanted something that generated true PWM, but allowed me to vary the frequency so that I could choose the best frequency at which to run for a given application. Let me know if you're interested.
> 
> --- In Homebrew_PCBs@yahoogroups.com, Richard Spelling <rls@> wrote:
> >
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> > Went to bed tired and annoyed I couldn't easily find a slower gear motor
> > for the laminator.
> > 
> > Dreamed about building a magical speed controller that would let me run
> > the existing motor infinitely slow.
> > 
> > Realized I could use "temporal kinetic and thermal stabilization" since
> > it's a worm gear motor.
> > 
> > I.E., I build a standard PWM controller but set the frequency real
> > sloowwwwww.
> > 
> > Imagine having the speed turned down real low. Along comes a pulse. The
> > motor spins up and turns the worm screw a revolution or two, then spins
> > down. The board advances a fraction of an inch. An in-determinant amount
> > of time later, along comes another pulse.
> > 
> > Yes, it's "jogging" the board forward and not continuous motion, but
> > between jogs it sits between the rollers long enough for the heat to
> > transfer through the paper.
> > 
> > I'm thinking about 10Hz.
> > 
> > Whatcha think? Just another crazy idear from Richard?
> > 
> > Now I just need to build the board.
> > 
> > Wait a second, I need my laminator to build the board to fix the laminator!
> > 
> > 
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