LED forward voltages have large production variations, and 20 mA is probably too bright with any modern LED. Be prepared to adjust that resistor. VCEsat is smaller than 0.7 V; you probably read the VBEsat value instead. And while these voltages are specified as negative values for PNP transistors (because the current flows in the other direction), the LED calculation still must use the absolute value for the voltage drop. 1 ohm is nothing; you could just as well leave it out. What is the current at which the relay is specified to blow up, i.e., the absolute maximum rating? How much current does the sensor need? You should be able to use a P-channel MOSFET with low RDS(on), such as, for example, the DMP2066, IRLML6401, or FDN338P.
↧
