ledmicrocontrollernpnpnptransistors
Let me first say I'm new to electronics. 🙂
So, my question is will this circuit work? I'm trying to light up a 2 lead bipolar LED using 2 pins on a microcontroller.
My theory is when the mcu pin 1 is high Q1 is saturated giving voltage, and when pin 2 is low Q4 is saturated connecting the circuit to ground and allowing LED1 to light up. And LED2 will light when pin 1 is low and pin 2 is high.
Am I on the right track? Or am I over-complicating this even? I do that a lot 🙂
Try holding the wire in an insulating holder - say on the end of a toothpick or wooden chopstick etc. Results are likely to be different.
You should provide a circuit diagram of EXACTLY what you are doing BUT if pin 6 is "floating" normally then your body will pick up mains hum capacitively from the surroundings and couple it into the pin. ALL input pins must ALWAYS have defined conditions if you want defined operation to happen. If you don't want defined operation then you can connect them any way you wish :-).
Change your load-driving PNP for a P-channel MOSFET. Also, you want a pull-up resistor on the gate of that MOSFET to ensure it switches itself off when the NPN switches off.
The NPN should also really have a pull-down on its base to keep it off when its input is HiZ or disconnected.
This is a circuit I use all over the place:
Best Answer
In your schematic, the PNPs need to be on the high side, and NPNs on the low side, all in the appropriate direction (+ → -). But you are overthinking it; using the MCU's standard push-pull outputs (which you've almost reconstructed in your schematic) with opposite levels will light the LED assuming the output voltage is high enough for the LEDs, and you can use alternating polarities to turn it the combined color.
simulate this circuit – Schematic created using CircuitLab