December 4, 2013
OK, here’s my project:
I’m putting this sound board into a helmet I’m making for Comiccon. (let’s say Darth Vader for the sake of simplicity)
Now in order to simulate Vader’s voice, I’m running the audio output pin through a mini guitar effects processor (Korg Pandora Mini: http://www.korg.com/us/products/effects/pandoramini/ ) and I’m trying to take what’s coming out of the Pandora (either from the stereo headphones or the mono ¼" Jack/TRS outputs) and put it in a speaker that’s also going to be hidden in the helmet, projecting forward or downwards.
I have 3 models of small speakers, including 2 from SparkFun (COM-09151 and COM-10722) and 1 in between those. I also bought the Small Surface Transducer (COM-10917) to try to see if I can use the resonance/vibrations of the plastic helmet as a sound-conducting device.
Now, I also have purchased the (BOB-11044) Mono Audio Amp Breakout with TPA2005D1, as I was foreseeing that the Pandora probably needed help to increase the gain in order to have enough volume out of the speaker.
Finally, everything is powered by 4xAA new Energizer rechargeable (1.25V) in a Battery Holder (PRT-12083). Measured ~5.0V on my meter.
I connected everything successfully, but here’s my PROBLEM: Whenever I start getting enough volume, I get INSANE FEEDBACK.
Now I understand that this is caused by the speaker going back into the mic, and so on, creating the infernal loop. This happens even if I put a good distance between the speaker and the mic, and if the speaker projects away from the mic.
When I use the headphones (instead of the amp+speaker) on the Pandora, it works flawlessly. Plenty of volume. So I infer that any gain problem would be AFTER the Pandora.
I feel that if I increase the gain on the Sound Detector or the Mono Audio Amp, it will just amplify the feedback… (didn’t try it, but that’s my guess, as changing the volume knob on the Pandora has that effect. Right now, feedback starts at volume 8/10 on the Pandora)
So… What can I do to eliminate this feedback, and keep a tiny footprint?
Is there a small board that eliminates high frequencies? (LP filter? EQ?… other techniques?)
Thanks for any help.
Will do test the Gate and report, once I receive the stuff.
Well, weirdly enough, best response I get with a white LED is when I connect it to the AUDIO out…
(with the power source being 4x AA 1.2V NiMH rech. batteries outputting 5.1 V at the meter…)
So the ENV and GATE outputs are of no use for me (and why I bought this board in the first place…)
However, the mike is extremely sensitive and of surprising quality (compared to similar cheap Chinese eBay boards), and the same goes for the cleanliness of the signal and amp path. Kudos for that!
Another bad side is the mike picks up ALL and ANY slight noise generated by touching the PCB or any friction on it.
This can render it useless for some applications. I’m trying to see if I can desolder it and put it back 1 mm or 2 away from the PCB, as it now seems to be in touch with it… hence maybe picking up more vibrations than it should… Will report if this works out. Also purchased the standalone Electret Capsule (BOB-09964) that has longer leads, in case I’m having too much trouble reconnecting the one that came with the board (which has very short leads, at it should…).
But in any case, this board is worth the money and is of great quality.
Just be aware of its limitations…
OK, got one of those… Am trying to connect it.
I see the 2 minuscule solder pads on one end, but is there a + and a - or it doesn’t matter?
Also: will this be more or less sensitive to signal than the mini speakers you sell here?
Just a heads up…
These things totally stink of badly formulated rubber.
Strong chemical scent that completely fills the room.
Almost makes my eyes water.
Reminding me of Mount Doom.
(hey, it rhymes!)
Hopefully, as time goes by and I air them out, the stench will die.
Otherwise, it’s a REALLY good price for a keyboard pedal!
Lovely!!! Thanks again!
Will do test the Gate and report, once I receive the stuff.
Is this microphone the same as for the Breakout Board for Electret Microphone (BOB-09964) you sell?
(100 - 10,000 KHz)
VERY USEFUL !!!! Thanks! (gotta love Sparkfun for that!)
So it looks like I should use 4x AA (1.2V) rechargeable batteries… =total of 4.8V.
Unfortunately, 4xAA alkaline would be 4x1.5v = 6V, which is too much for the Sound Detector (Hookup Guide says max is 5.5V)
Any other options for power source? It can’t be much bigger that 4xAA, and can’t be attached to a wall or computer (goes in a helmet)
Otherwise, here are the optional solutions I can see: (feel free to suggest more ideas…)
1) I could use a white LED with a purple screen in front of it, to achieve the desired effect. But…
Should I go for a normal brightness white LED with a Vfwd as close to 2V as possible (which I’d have to order, but my time is limited),
or, could I use this Super bright white LED that I have, which is Vfwd=[3.2 - 3.4]V and 20mA (18,000 MCD) ??
Update: upon a search on eBay and a few sites, this kind of low-voltage white LED seem very rare…
2) I have also purchased your “LED - Assorted (20 pack)” (COM-12062), which includes basic blue LEDs which were described by notexactly as: “Very bright at 9 mA (2.00 V over 220 Ω resistor)”. If I find a suitable color screen to go in front of it, maybe that could also do the job… Would that likely react well if plugged straight on the ENV output? (with a resistor in between?)
3) I could modify the Sound Detector circuit by increasing the Gain (changing the R3/R17 value on the board as per the Hookup Guide) to try to get more signal out of this board… but not sure if it would give more V…
Not sure how I would implement a buffer or additional gain for the LED though.
Would I just put some Amp between the ENV output and the LED ?
(I also purchased at the same time the Mono Audio Amp Breakout (BOB-11044) which is TPA2005D1-based, would that board work for that or is there a better board?)…
And by buffer you mean like a resistance between the Amp and the LED ?
Sorry, I’m not an electrical engineer, just a hobbyist with a basic understanding of stuff and good learning skills.
(which is why I love Sparkfun so much!!)
So if anyone has pointers to similar applications and how-to’s, please mention it!
, it’s definitely worth paying a bit more to get quality tools. Not having that spring jutting out is already an improvement, of course :)
Each blade is actually a tiny little Samurai Katana blade!!! Beware!
Can anyone tell me what kind of current and voltage is coming out of the ENVELOPPE output please?
I’d like to use it to drive the Violet LED (COM-12704) that is 30 mA and [3.0 - 3.6]V
Will that be ok right out of the box, or will I need something in between.
(I plan on powering the Sound Detector with either standard rechargeable (1.2V) 4xAA batteries, or 3xAA (1.5V) premium alkaline)
e wondering: These should fit the 12mm holders listed below. Or at least in theory.
The Practical Working Voltage for these is actually 1.15 V., so using 3 of these probably would’ve been better.
Not sure about the mAh rating though… But would really like to know as well.
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