home *** CD-ROM | disk | FTP | other *** search
/ NetNews Usenet Archive 1992 #27 / NN_1992_27.iso / spool / sci / electron / 19032 < prev    next >
Encoding:
Text File  |  1992-11-17  |  1.8 KB  |  38 lines
  1. Newsgroups: sci.electronics
  2. Path: sparky!uunet!melpar!doherty
  3. From: doherty@melpar (Kevin Doherty)
  4. Subject: Re: 555timer/flasher
  5. Organization: E-Systems, Melpar Division
  6. Date: Tue, 17 Nov 1992 12:03:36 GMT
  7. Message-ID: <Bxv061.157@melpar>
  8. References: <ahs1h2a@rpi.edu> <1992Nov14.222449.15544@cis.ohio-state.edu> <1992Nov16.111214.1@levy.fnal.gov>
  9. Lines: 27
  10.  
  11.   that is a circuit i have memorized:
  12.                     
  13.                                            vcc
  14.                                             |
  15.                              +----------+   |      
  16.                       +------+ 1      8 +---+---/\/\/-+       
  17.                       |      |          |   |    r2   |
  18.                       | +----+ 2      7 +---|---------+
  19.            d1    r3   | |    |          |   |         |
  20.          +-|>|--/\/\/-|-|----+ 3      6 +---|-+-/\/\/-+
  21.          |       +----|-+    |          |   | |  r1
  22.          |       |    | | +--+ 4      5 +-x | |
  23.          |     --+--  | | |  +----------+   | |
  24.          |     --+--  | | +-----------------+ |
  25.          |    c1 |    | +---------------------+            
  26.          +-------+----+                                    
  27.                       |                                     
  28.                     -----                                  
  29.                      ---                                   
  30.                       -                                    
  31.  
  32.   it works by charging c1 to 2/3 vcc through r1+r2, then discharging c1 to 
  33. 1/3 vcc through r1 alone.  don't recall the r1/r2/c formulas offhand, but
  34. you should be able to figure them out from the above.
  35.   notice also: the duty cycle is set by the ratio of r1 to r1+r2.  you can't
  36. quite get a 50% duty cycle, although you can get close.  (actually with some
  37. circuit mods one can get any duty cycle desired)
  38.