Asked — Edited

Sound Activated Led.One More Time

Hey guys up for discussion: I am looking to have a single .wav file trigger an LED. This is for my Gargantuan project. I’d like to have the sound effect of his cannon trigger the LED in his cannon. I want this seperated from all other sounds. I.e no other sounds should activate this LED.

I looked thru Rich’s tut on using the mic, but I want to isolate to one wav file. Any ideas suggestions would be greatful.



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Ok I’ll take a look in the morning... I think my brain is fried for tonight! Thanks.


Lol understandable. You’ve been unstoppable!

You can have a script run with the soundboard. That can control the led.


There needs to be fried egg emoji! LOL!

I'm speeding along because my 6 year old comes home from school asking "...Is it done yet, is it done yet?" stress

Quick question. I connected up a LED to the EZB and noticed that the LED is fainter on the PWM setting at 100% , I even removed the resistor to get more brightness. But then was somewhere Rich had mentioned his Tip120 & Tip122 Transistor Switching Circuit.

Will this pull up voltage to get a brighter LED?


As long as you are over the forward voltage threshold (usually 3V for Blue LEDs and 1.9V for Red LEDs) all that matters in terms of brightness is the current you are putting through the LED. 3.3V is fine for any LED, increasing the voltage won't make the LED brighter.

Keep in mind the output of the EZ-Bv4 digital pins is limited to 10mA of current to drive an LED.

You can certainly use a simple 2N3904 or 2N2222 transistor connected to the EZ-B digital pins and to the LED in order to put more current through it. Please make sure you know the max current for your LED in particular. Most 5mm LEDs are 20mA max. Use the ohms law calculation V=IR to calculate your resistor value.

R= V/I R = 3.3V/20mA = 165ohms

200ohms would be the closest common value if you are connecting to 3.3V power from the analog input section of the EZ-B.

So yes, you can get the LED brighter using a transistor circuit.


Thanks Jeremie. I’m connecting to D23 so I can use pwm. It’s a full 7.4volts. But when I connect the led from Riches tut on sound to control brightness/falloff on the LED I get a substantially dimmer LED than if I control it with pwm directly from that control. I’ve used a 220 ohms resister using the supplied fv and mA rating. But you have reminded me that the signal will be no more than 10ma and these LED are rated at 20mA. I’m going to try building his TIP 120 transistor board ( since I already have several here at the shop) to see if I can get it up.

****edit Rich’s Tip 120 board worked amazingly well. LED is now at full brightness. Now just need to explore isolating one sound bite with the cannon led light and decay.