Electronics > Beginners
Beginner Project Fun - Voltage divider + 3 separately switched LEDs and a buzzer
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fedaalis84:
Just wanted to share some fun I had with this little project & my very first intentional circuit.
My initial concept was to connect 3 LEDs (each @ 15mA and their corresponding voltages) to a button, and when each button is pressed, the corresponding LED would light up and make a noise on the buzzer/speaker.
Step 1: Measure the voltage drop across each LED @ 15mA using a bench power supply.
Red: 2.09V
Yellow: 2.14V
Green: 3.01V
Step 2: Create a voltage divider, using my 5.07V phone charging pack as the power supply, to obtain the necessary voltage and current for each LED...
This is what I came up with:
I used a wacky combination of 100 ohm & 10 ohm resistors in and not in parallel to obtain similar resistance ratings between each node.
This was a great success! And I got similar voltages & current to what I was expecting.
Step 3: Build the circuit (No pic cause I tore it down before thinking to take one).
FAIL!!!!!
Problem? The buzzer has its own VERY HIGH (~5.2M) innate resistance... Completely slipped my mind to even think of that.
Step 4: Completely re-evaluate the circuit.
Ultimately I wound up with this:
Which is basically the same circuit with NO voltage divider, and a 100ohm resistor in parallel prior to the buzzer.
BINGO!!! Works & each LED is at least limited in voltage and current enough not to blow out (But dissimilar to my desired current):
20mA on the green LED & 32mA on the yellow & red.
Overall, fun project...
Nobody I know personally would care - LOL. So figured I would share here...
[Update] - I realized now that a 330 ohm resistor in parallel with the buzzer would provide a better current across the LEDs. Now I get ~10mA in the green LED circuit, and ~13mA in the red & yellow circuits.
Wimberleytech:
Hey, that's great! When I started in electronics, there were no LEDs. I would do similar things with small incandescent bulbs, toggle switches, and mechanical buzzers. Keep it up!!
fedaalis84:
Too cool! Thanks Wimberleytech!
I am addicted. I have gone nuts on tools that far exceed my capacity to use them yet. Lol.
LEDs/Breadboards are NICE!!!
Originally I got hooked on this trying to fix a broken stereo (which I utterly destroyed with my poor technique and a cheap soldering iron).
But I think I have more fun learning about basic circuits and Ohm's law, and eventually want to start trying to get a handle on KVL & KCL.
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