- Joined Nov 10, 2018
Hello, it is another of these days that I am trying to resolve the obvious. Something that should work immediately it does not. I am trying to blink the two leds alternatively using a pnp transistor for one of them. The pnp does not fully turn off. When one of leds (the one connected straight to the 555 output) is on the other is also on but a little less, it fades a little but it does not turn off completely. I used both configurations as you can see, one is on the emitter side and the other on the collector. Both of them the same, I tried lower resistor for the pnp base down to 820Ω with no luck. Transistor is 2N2907. If I use the 2N2907 and led alone though (without the other led connected) it works, it switches off, and with a resistor from its base to ground it switches on, perfect. Why when it is connected to another load (like the led without pnp) it does not switch off? It looks like the led without the pnp "steals" all the current from the pnp and does not let it switch off completely but this does not make any sense since they are just two components connected in parallel.
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