So I'm pretty new at this, so I'm sorry for any dumb questions/statements.
I'm trying to build a puzzle box where you activate a circuit with a reed switch using a hidden magnet. Activating this circuit needs to make a sound and make 2 LED's light up. I'm using a 9V battery, 2 green LEDs (no datasheet available, no multimeter of potentiometer either. But the operating voltage range is 2.9-3.6 V at 20 mA) and a mechanical buzzer rated at 2-4 V at 20 mA.
So here is my thought process: 2 LEDs with a voltage drop of about 3V, will leave about 3V for my buzzer (well in the operating range if the LEDs happen to drop more/less). Since all of the components are using 20 mA, I can safely put them in series. The only thing I'm not sure about, is the current that will flow through. I know you normally would place a resistor in front of the LEDs to limit the current, because the LEDs are basically a dead short, but will the buzzer do the same job?
- Is this possible: all of them in series without a resistor? Will this have any effect on the brightness/sound level?
- if not, can I just put the 2 LEDs in series with a resistor (needs about 140-150 ohm resistor in front of it) and those LEDs in parallel with the buzzer (with a 300 ohm resistor?
- If both of them are wrong, what's the solution?