From: sebastiasebas@gmail.com   
      
   El dilluns, 22 octubre de 2018 16:48:23 UTC+2, default va escriure:   
   > On Sun, 21 Oct 2018 16:50:20 -0700 (PDT), sebastiasebas@gmail.com   
   > wrote:   
   >   
   > >Hi - I got a brand new solar cell "Eco Line ES10M36".   
   > >   
   > >In my garden, under full sun it provides 21 volts and 500 mA,   
   > >and under big shadow it gives 18 volts and 30 mA.   
   > >   
   > >Load is a 24 volt bulb lamp in series with the Fluke.   
   > >   
   > >As the voltage margin is small, I want to detect the intensity   
   > >to determine if there is sun or not.   
   > >   
   > >What electronic circuit would you recommend to do it ?   
   > >   
   > >If I place 2 resistors conected in serial,   
   > >the voltage drop will have the same small margin the cell has ...   
   > >   
   > >Thanks.   
   >   
   > Use a voltage comparator - basically an op-amp with an open-collector   
   > output for driving a little bit more current.   
   >   
   > The 18-21 volts could be easily discriminated (down to a few   
   > millivolts) but you'd need something like a precisian reference that   
   > doesn't fluctuate with the panel's voltage output.  That could be as   
   > simple as a zener diode or just use a 3 terminal regulator to power   
   > the indicator circuit and reference against a voltage divider.   
   >   
   > (bearing in mind  that if you have a 5 volt regulator, for instance,   
   > the comparator may be destroyed if you try to plug 18 volts into one   
   > of the comparator inputs, the voltage divider takes care of that but   
   > another diode to clamp the voltage at a safe level would also be nice)   
      
   mr Default : there must NOT be a 5 Vcc regulator : the circuit has to get   
   voltage from the solar cell, which is the only power available on site.   
      
   Thanks. Ceba.   
      
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