PDA

View Full Version : Advice on Teensy audio input voltage



nyarlathotep
05-03-2013, 08:19 AM
I'm interested in using a small microphone with a Teensy 3.0, roughly like the Arduino Wind Instrument (http://www.instructables.com/id/Arduino-Wind-Instrument/#step1).

First, what voltages do the Teensy 3.0 input pins want? I'm aware the Teensy 2.0 like normal Arduino 5V inputs just fine. The IRemote thread (http://forum.pjrc.com/threads/15121-IRremote-lib-on-Teensy-3-0) suggests the Teensy 3.0 like 5V inputs too, yes? I presume analog pins should range from 0-5V too, yes?

Second, any recommendations for small microphones good at dealing with low frequencies? I'm wanting to FFT anything from human speech to dance music, not sure if I should use a microphone with a larger range.

ploveday
05-03-2013, 10:13 AM
The Teensy 3.0 is a 3.3V device, and its inputs are not 5V tolerant, so make sure you're not using anything 5V without appropriate precautions.

As for the analogue in, well you can't exceed 3.3V, but you can provide a different (lower) Vref should you need to.

nyarlathotep
05-03-2013, 11:56 AM
Alright, I suppose the IR receivers can simply be fed 3.3V from the Teensy's 3.3V power pin. For microphones, there are many boards that supposedly want no less than 4 V, but the ISD1820 (http://www.eimodule.com/download/EIM353_ISD1820_Module_Manual_V01.pdf) takes 3.3V happily.

PaulStoffregen
05-03-2013, 03:56 PM
Most IR receiver modules have open collector output. Many IR modules can run from 3.3 volt power. But even if you have one that must run on 5 volt port, the output is zero and whatever voltage the pullup resistor makes. Just connect the pullup resistor to 3.3 volts.

Those little microphones output only a tiny voltage. Usually an amplifier is needed to increase to something an A/D can read. With Teensy 3.0, you might try using the internal reference which makes the input 0 to 1.2 volts. Just use less gain on the amplifier if the signal is too large.