Machine Independent Storage Idea...

Dave McGuire mcguire at neurotica.com
Sat Dec 9 17:42:02 CST 2006


On Dec 9, 2006, at 11:45 AM, Chuck Guzis wrote:
>> Actually My first draft was a 555. By the time all the  
>> requirements were met,
>> the component count had gotten out of hand. 7420,555,7438,handfull
>> of descretes... a single 20 pin package a crystal and a transistor  
>> didn't
>> seem like overkill.
>> And it would handle the creeping feature bloat My projects suffer  
>> from ;^)
>
> I happened to mention this to a customer yesterday who sells
> computerized scales and the like.  His comment was that a PIC was
> very competitive with a 555, when one considered the external
> discrete component count and glue--although he admitted that a number
> of his products still use lots of 555s.

   I can see that being the case when you need multiple related pulse  
trains or something like that...but to replace a single 555, I find  
this very difficult to believe.  I've designed both into commercial  
products in the last few years...Sure, PICs are super cheap, but 555s  
in thousand-unit quantities cost less than a dime.  As for the  
discrete components...Assuming you're running the PIC in internal  
oscillator mode (which saves you a crystal and two capacitors), you  
need a pullup resistor to MCLR, while a typical 555 oscillator  
circuit needs one or two resistors and a capacitor...so a capacitor  
and possible additional resistor.  Add in the step of having to  
program the PIC (and maintain the codebase, documentation, etc)...no  
way.

   It seems to me that many of these types of attitudes stem from the  
"if it's old, it's bad, and if it's not new, it's old" mentality that  
has been adopted by the obedient mass of consumers.

           -Dave

-- 
Dave McGuire
Cape Coral, FL






More information about the cctech mailing list