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Microphone Recommendations?

posted Jun 29, 2016 18:34:15 by BrandonMoore
Hello there, I am currently searching for a good mic to use with my movi board. It will be used inside a Motorhome/RV so it will be tucked away somewhere and the mic will be sitting on a countertop or something of the like. I need a mic that has about a 20-25 ft pick up radius. I have been looking but cannot find anything that works for my needs and doesn't require phantom power. Any help would be appreciated, thanks.
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8 replies
GeraldFriedland said Jun 30, 2016 02:50:13
Well, microphones for this distance usually need an amplified signal, that's why they all require phantom power. Too bad MOVI's onboard microphone doesn't work for you.

Without knowing much about your setup, an amplified microphone like this one:
might be worth giving a shot.

You can power it with MOVI's external power supply (by using the microphone power jack in series with the Arduino power plug). However, you will need to build a small attenuator circuit to attenuate from line level to MOVI's microphone jack level. This is described by the "external microphone" topic posts in our forum.

Maybe that helps...
[Last edited Jun 30, 2016 02:54:36]
avatar said Jul 06, 2016 19:22:55
I just did a test of the MOVI board running the Example program (SimpleDebug). I tested the program using the built in microphone with a Television on an its output volume set higher than a normal conversation level. I also had an air conditioner running for an added challenge. The MOVI Boards built in microphone did pretty well if I spoke to it from about 1 foot away although after the Arduino command and the recognition beep it could take several seconds for the voice recognition to trigger the response to a sentence. After several tests. I turned the power off and connected an Audio-Technica Shotgun Microphone ATR6550 to the external Microphone port. This Microphone is powered by a single AA battery and has two positions one for near and one for far sensitivity. Note: Before I connected the Shotgun Microphone I tested the Mics output voltage with a Multi-meter set to AC voltage, Even when I yelled into it I never saw more than about 350 mV on either power setting. So I figured it would be ok for the MOVI A13 chips inputs without needing the two attenuation resistors and a capacitor. The results of this test were good. Them MOVI responded much faster and more accurately at distances of two to five feet. That's not bad for such a noisy/semi normal environment.
[Last edited Jul 06, 2016 19:24:02]
GeraldFriedland said Jul 07, 2016 14:11:33
That sounds good indeed!

it could take several seconds for the voice recognition to trigger the response to a sentence

Playing with the threshold will help that problem. Try adding

(Or 15 or 20) after the train() command.
[Last edited Jul 07, 2016 14:11:48]
Connor Cook said Aug 24, 2016 14:40:32
I am attempting the same sort of thing that the first commenter was. After looking at the microphone you suggested ( ), I was able to figure out how to power the microphone through the Arduino, but I don't know how to connect the other part of it to the attenuator circuit and then to the MOVI board itself and have it be used instead of the original microphone on the board.

Any help is appreciated.
Dylan said Aug 25, 2016 05:05:16
There is a long discussion about a powered external microphone here:

Look at the response from Gerald in response #9. I built one based on those specs and it works well. In theory, plugging in a microphone into the microphone jack disables the internal microphone. There is currently some question as to whether or not that is happening completely or not as a few of us are experiencing some odd side effects using an external microphone. Regardless, this is a good place to start to build a circuit as describe in that thread.

Connor Cook said Aug 25, 2016 11:23:51

Did you use the Adafruit DGC microphone that was linked in the post? I have an external microphone with two power connections, which I would connect in series to power the microphone, then it has two wires. I don't know how to connect these wires to the attenuator circuit, and then attach that circuit to the microphone jack.

My question is how to physically connect these things. A picture of your set up would be extremely helpful.
Dylan said Aug 25, 2016 17:07:37
I used the one recommended by Gerald in that thread:

Gerald is very particular about the type of mic that is used and prefers that we use one with the same MAX9814 chip that MOVI has onboard, hence the adafruit mic. It might be worth the $7.95 plus some effort in building a box for it for the piece of mind that you'll get the best possible support from the Audeme guys. For the box, I used one of those slide top mint boxes lined with some plastic salvaged from an old ribbon cable. Be aware though, the mic is smaller than you will imagine looking at the pictures - the way adafruit laid it out, it is very difficult to find screws and nuts that are small enough to secure the mic to the box, and to drill holes precisely enough right beside the large hole for the electret itself.

A useful photo would be difficult to take because the solder points are all barely visible. It kind of looks like this:

|       GND|---------------------------------------------------- To Arduino GND ----------------------\
|       Vdd|---------------------------------------------------- To Arduino 5V                        |
|      Gain|               (long 8-10 foot cable)                                                     |
|       Out|---------------------------------------------------- To "Line in" on attenuator circuit   |
|        AR|                                                     To GND on Attenuator circuit  -------/

Mic lvl out on the attentuator circuit gets split and soldered to both the tip and the center ring on a 3.5mm stereo plug. GND on the attenuator circuit goes to the final ring (called the Sleeve I believe). I may have overdone the grounds the way I did it there; I'm no electronics expert.

I actually used a mono jack that looks like this:

and used a mono to stereo converter because I was able to just barely solder the two resistors and capacitor inside the mono jack housing so it's all compact and neat. This isn't for the faint of heart though, it's extremely tricky and you need to have a really good electronics place you can source a tiny capacitor from if you want to do it this way.

I hope that helps a bit.
[Last edited Aug 25, 2016 17:14:44]
Connor Cook said Aug 25, 2016 18:46:07
Thanks Dylan, that was super helpful. However, I think I am going to try a pre-amped microphone and attenuate it. I am trying this at my job and I really don't want to break anything.
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