From: gherold@teachspin.com   
      
   On Wednesday, May 15, 2019 at 3:59:27 PM UTC-4, Phil Hobbs wrote:   
   > On 5/15/19 2:23 PM, Look165 wrote:   
   > > A bad friend which act only in one way !   
   > >    
   > > Phil Hobbs a écrit le 15/05/2019 à 20:05 :   
   > >> On 5/15/19 1:26 PM, Look165 wrote:   
   > >>> For an alarm, do you care to 10ms for instance ?   
   > >>>   
   > >>> Phil Hobbs a écrit le 15/05/2019 à 19:20 :   
   > >>>> On 5/15/19 1:14 PM, Look165 wrote:   
   > >>>>> Yes, it can.   
   > >>>>> A photodiode takes time to turn on or off, about the same a LDR takes.   
   > >>>>> LDR are reversible, standard photodiodes are only one way.   
   > >>>>>   
   > >>>>> Cursitor Doom a écrit le 15/05/2019 à 16:30 :   
   > >>>>>> On Wed, 15 May 2019 11:15:18 +0200, Look165 wrote:   
   > >>>>>>   
   > >>>>>>> A LDR reacts in some ms when the light's  wavelength is in the   
   > >>>>>>> operating   
   > >>>>>>> range.   
   > >>>>>> You really can't beat a photodiode, though.   
   > >>>>>>   
   > >>>>>>   
   > >>>>>>   
   > >>>>>>   
   > >>>>>>   
   > >>>> A fast photodiode will respond in picoseconds.  Even slow ones are in   
   > >>>> the tens-of-nanosecond range if used with the right transimpedance amp.   
   > >>>>   
   > >>>> They're also highly linear and stable, neither of which is true of CdS   
   > >>>> cells.   
   > >>>>   
   > >>>> Cheers   
   > >>>>   
   > >>>> Phil Hobbs   
   > >>>>   
   > >> Of course not, but you gave Bad Info about photodiodes, who are sort of   
   > >> friends of mine. ;)   
   > >>   
   > >> Cheers   
   > >>   
   > >> Phil Hobbs   
   > >>   
   > >    
   > Along with a lot of other stuff, they've been paying my bills since    
   > 1983ish.  Friends don't come a lot more faithful than that. ;)   
   It's terrible PC-wise to say, but it's important to be    
   biased when it comes to photodiodes. :^)   
      
   George H.    
       
   >    
   > Cheers   
   >    
   > Phil Hobbs   
   >    
   > --    
   > Dr Philip C D Hobbs   
   > Principal Consultant   
   > ElectroOptical Innovations LLC / Hobbs ElectroOptics   
   > Optics, Electro-optics, Photonics, Analog Electronics   
   > Briarcliff Manor NY 10510   
   >    
   > http://electrooptical.net   
   > http://hobbs-eo.com   
      
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