From: ehsjr@verizon.net   
      
   On 3/14/2024 12:31 AM, UFO wrote:   
   >   
   > Been hearing that a lot for responses.   
   > Since the LED needs I guess 1.5V to be on,   
   > and can burn out with too much voltage, it   
   > did not seem to be a suitable option.   
      
   Here's a diagram:   
      
   +6V ---resistor---LED---ground   
      
   Assuming a red LED you need roughly 1.5 volts   
   applied to it. That means the resistor has to   
   drop about 4.5 volts. We want the current to   
   be 20 mA or less, so we'll choose 10 mA. The   
   formula to determine the resistance is R=E/I   
   where E is the voltage to be dropped and I is   
   the current through the LED. So R = 4.5/.010   
   That equals 450 ohms, and the closest standard   
   value is 470 ohms, which will work just fine.   
   A 1/8 watt resistor is the smallest trough hole   
   size and may be easier to fit in than a 1/4 watt.   
   It depends on what you have on hand that will physically   
   fit - the resistor will use only about .05 watt   
      
   The current through the LED does not have to   
   be exact - anything from say 2ma (often much   
   lower, depending on the LED) to 20mA will light   
   it up nicely.  If you want to use a white LED   
   you can. A white LED needs roughly 3.2 volts   
   so the resistor value changes to roughly 280 ohms,   
   which means using a 270 or 330 ohm standard size.   
   I'd use 330.   
      
   Ed   
      
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