This question is probably Electronics 101. I am not sure if questions this basic should be asked in this forum. If there is another site that is more appropriate, please point the way.
Attached is a solar path light schematic that I'm having a hard time understanding. In this circuit during daylight hours, the solar cell is charging the batteries and the LED is turned off. When the solar cell is no longer providing current, the LED comes on with the batteries providing current.
What I don't understand is why the transistor Q2 does not come on (and it shouldn't because we don't want the LEDs on during daylight hours) when the solar cell is providing current. I don't see why there's not enough current through Q2's emitter and base to turn that transistor on. Isn't there current through the emitter, base, through R3 and back to the solar panel?
Now don't get me wrong, I'm not saying the circuit is not correct. I am ONLY saying I don't understand why it works. Here is the website's explanation which I'm having trouble grasping:
Apparently I need to be spoon-fed this explanation because I still do not see why "this prevents current from flowing into the base of transistor Q2.
Attached is a solar path light schematic that I'm having a hard time understanding. In this circuit during daylight hours, the solar cell is charging the batteries and the LED is turned off. When the solar cell is no longer providing current, the LED comes on with the batteries providing current.
What I don't understand is why the transistor Q2 does not come on (and it shouldn't because we don't want the LEDs on during daylight hours) when the solar cell is providing current. I don't see why there's not enough current through Q2's emitter and base to turn that transistor on. Isn't there current through the emitter, base, through R3 and back to the solar panel?
Now don't get me wrong, I'm not saying the circuit is not correct. I am ONLY saying I don't understand why it works. Here is the website's explanation which I'm having trouble grasping:
Anybody might ask, "What keeps the LEDs from turning on during the day?"
The answer is that the current provided by the Solar CD seeks out any open path. Most of the current flows directly from the Solar CD and into the batteries. But a small amount of current flows through 2.2k resistor R1, where it meets the higher resistance of 10k resistor R2. An even smaller amount of current flows through R2; the rest of this current flows into the "base" lead of transistor Q1, which "turns on" Q1, creating an open path for current to flow through 2.2k resistor R3 and then through Q1 from collector to emitter. This prevents current from flowing into the base of transistor Q2. If current flowed into the base of Q2, the LEDs would turn on.
Apparently I need to be spoon-fed this explanation because I still do not see why "this prevents current from flowing into the base of transistor Q2.