[Wbo2] simple warning LED display

[James Holland]

If stoich is OK then that makes things a lot simpler, 2.5V is a 'standard' voltage and an LM139 can sink enough current for an LED. If you like I will sketch out a circuit that you could build on some veroboard.
  ----- Original Message ----- 
  From: Tommy 
  To: 'James Holland' ; wbo2 at diy-efi.org 
  Sent: Sunday, September 18, 2005 7:34 PM
  Subject: RE: [Wbo2] simple warning LED display


  Sorry James, and everyone else, but this is way over my head.  I have a very basic understanding of electronics.  Basically I know the difference between a resistor and a capacitor?.but not beyond that to any certainty.  The 15:1 doesn?t have to be precise, the led can trigger at stoich ~ 2.5v.  I only want the led to come on at this voltage or higher.  I shouldn?t be anywhere near stoich at WOT so if the light comes on, I know there is a problem, ie. Additional injectors failed, clogged filter, etc. 

   

  Operating temp?  Not a clue.  

   

  I was figuring this could be done in a simple circuit, but not so sure anymore.  Atleast simple to me.

   

  Thanks again

   

  -----Original Message-----
  From: James Holland [mailto:J_Holland at btopenworld.com] 
  Sent: Sunday, September 18, 2005 12:50 PM
  To: Tommy; wbo2 at diy-efi.org
  Subject: Re: [Wbo2] simple warning LED display

   

  I spoke too soon, I just had a look at the actual numbers. The difference between stoich and 15:1 is only around 0.025V which is around 1%, that would need a very high degree of accuracy, a precision reference, a comparator with a pretty good spec (LM139 maybe) and 0.1% resistors. It might be possible, what sort of operating temperature range are you aiming for?

    ----- Original Message ----- 

    From: James Holland 

    To: Tommy ; wbo2 at diy-efi.org 

    Sent: Sunday, September 18, 2005 6:02 PM

    Subject: Re: [Wbo2] simple warning LED display

     

    Consider using a comparator circuit, something like an LM319 would be OK. 

      ----- Original Message ----- 

      From: Tommy 

      To: wbo2 at diy-efi.org 

      Sent: Sunday, September 18, 2005 3:29 PM

      Subject: [Wbo2] simple warning LED display

       

      I?ve been on a search to find a very simple LED display for a wideband unit.  What I want is a simple 1 led warning light that will trigger when I get a lean voltage.  I don?t want to monitor the range all the time.   I just want a single led to come on with a AFR of 15 or greater.  A light that when at WOT, I?ll know something is wrong without having the interior of the car look like a disco club.  If anyone has any ideas, links, past projects, etc I would be very appreciative.

       

      Thanks

      Tommy

       

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