I am working with a one battery Joule thief chip that can be controlled by the voltage on Pin 1. Voltage above .5 volts turns it off and lower voltage turns it on. Since a positive voltage would not turn it on, I added a PNP transistor to send positive voltage to the pin until a signal from a device turns the transistor off. Then the CDS can determine if it should light as shown in the circuit below:
I wanted to add motion detection to turn on the LED driver, but the PIR sensor module needs more than 3 volts to run properly. Although it sends about 2.4 volts to base of the PNP transistor, it is just turning it off. That part of the circuit has worked well.
Using the same logic for a low input signal, I figured that the reverse would work with a NPN transistor. Should I set the base to ground or the positive battery? I am afraid that a higher voltage through the 4.7 K resistor will end up on the battery bus as both circuits have the same common.
Thanks!
I wanted to add motion detection to turn on the LED driver, but the PIR sensor module needs more than 3 volts to run properly. Although it sends about 2.4 volts to base of the PNP transistor, it is just turning it off. That part of the circuit has worked well.
Using the same logic for a low input signal, I figured that the reverse would work with a NPN transistor. Should I set the base to ground or the positive battery? I am afraid that a higher voltage through the 4.7 K resistor will end up on the battery bus as both circuits have the same common.
Thanks!