From: gherold@teachspin.com   
      
   On Tuesday, May 14, 2019 at 11:22:42 AM UTC-4, default wrote:   
   > On Tue, 14 May 2019 07:19:09 -0700 (PDT), George Herold   
   >  wrote:   
   >   
   > >On Monday, May 13, 2019 at 10:22:59 PM UTC-4, AK wrote:   
   > >> Electronic can be quite frustrating.   
   > >>   
   > >> I put together a circuit for a laser alarm.   
   > >>   
   > >> It does not work.   
   > >>   
   > >> There is no way to tell if a design will be successful even if you follow   
   the authors exact directions.   
   > >>   
   > >> I will keep plugging away and reading Practical Electronics for Inventors.   
   > >>   
   > >> :-)   
   > >   
   > >Hmm, Well a common pitfall when starting in electronics is to copy all   
   > >of some circuit.  Plug it in and find it doesn't work.   
   > >A better approach would be to build up one little part of it.. make sure   
   > >you know how that little part is supposed to work, and confirm it's   
   > >working as expected.  (Or not and go figure out why.)   
   > >Then add the next little piece.   
   > >   
   > >Do you have an oscilloscope?   
   >   
   > Here is the schematic   
   > https://cdn.makezine.com/uploads/2013/11/laseralarm.jpg   
   >   
   > He's using the 555 as a simple latch to turn on the buzzer until the   
   > toggle switch resets it.   
      
   OK, I haven't used a 555 in decades, and have mostly forgotten how it works.   
      
   Maybe he could try a comparator and a S/R flip flop.. Or   
   just a comparator to LED + resistor.   
      
   George H.   
      
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