|
|
On Sat, 22 Apr 2006 10:32:24 -0500, John Fields <jfields@xxxxxxxxxxxxxxxxxxxxx>
wrote:
>On Sat, 22 Apr 2006 22:39:05 +0800, budgie <me@xxxxxxxxxxx> wrote:
>
>>On Fri, 21 Apr 2006 22:22:00 GMT, Rich Grise <richgrise@xxxxxxxxxxx> wrote:
>>
>>
>>>>> Did you notice Ra for 50%? Zero. The chip will try to discharge the
>>>>> power supply. ;-)
>>>>
>>>> It had crossed my mind as odd. :) I didn't think that through though...
>>>
>>>I guess it's just from all of these billions and billions of years of
>>>experience. ;-) Or maybe because I had tried it once, so I already knew
>>>the answer, and was just tweaking you. ;-)
>>>
>>>I was seriously curious how the program would deal with it, and I guess
>>>it's another example of why computers will never replace people. ;-) ;-)
>>>
>>>One time, I think (it's kinda lost in the mists of time) I actually used
>>>two resistors with a diode in series with one of them in place of Rb, and
>>>got pretty durned close to 50%, but I like the one-resistor, schmitt-
>>>triggeroid version more, I think. :-)
>>
>>There is a "standard" circuit for achieving 50% duty cycle with a 555, and it
>>does include a diode. Used it once before I decided 555's were crap.
>
>---
>Well, let's see...
>
>For way less than a dollar you get an astable or a monostable
>multivibrator, a couple of comparators with a nice internal pretty
>much isothermal voltage divider that you can mess with if you want
>to, a totem pole output that you can get a couple hundred milliamps
>out of, an open collector NPN, and a RESET input.
>
>And... you can get them anywhere, everybody makes them, and they're
>not likely to stop making them anytime soon.
>
>And... you can get it in CMOS.
>
>Crap you say? LOL!
Crap repeatability.
|
|