Key things to know:
=== Threshold ===
- Starts at 1.0v, and 0.1mA
- Best at 1.2V, and 10mA
- Effective resistance at that = 120 ohms
- Long term life is reduced above 10mA.
- R = (Vapp - Vforward) / Iforward
- R = (4.1 - 1.2) / 0.010 = 290 ohms !
=== Threshold adjustment ===
- Threshold can be adjusted by putting resistor in series:
- === or, redrawn so it make sense to a newB ===
- BUT NOTE ... values are not 2.2K and 2.2K (which don't make sense).
- Instead (for example) R2 could be 240 ohms (2.4V / 0.01 A) ... and R1 would be 170 ohms (4.1-2.4)/0.01.
- This would mean total circuit resistance (when LED on) of 250 ohms (170 + parallel 240 and 120) so total circuit current of 4.1/250 = 16mA. R2 gets V/O = 2.4/240 = 10mA of the current, and the LED gets 2.4/120 = 6mA of the current.
