I’m trying to light two 2.2V 20mA LEDs using a 9 volt battery, a PIR motion sensor and a transistor.
Wired as shown with 9 volts applied at the collector and the 3.3 volt signal from the PIR applied at the base of the transistor, the output is only about 2.6 volts which will only light one LED.
My idiot brain thought the PIR would output a signal when motion is present, then the transistor would act as a switch and I would get approximately 9 volts at the emitter. I could then use a resistor to knock it down to about 4 volts to light the two LEDs.
Apparently there is a large voltage drop at the transistor resulting in a 2.6 volt output.
- Does anyone know why I only get 2.6 volts coming out of the transistor?
- Any idea how I can correct this to get what I want?