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Gadget Freak
Gadget Freak Case #240: MEMS Mics Up Telescope
5/9/2013

Jerald Cogswell mounted a precision MEMS microphone in a satellite dish's focal point so it can feed its signal to an amplifier that enables simultaneous recording and monitoring via headphones.
Jerald Cogswell mounted a precision MEMS microphone in a satellite dish's focal point so it can feed its signal to an amplifier that enables simultaneous recording and monitoring via headphones.

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William K.
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Platinum
A much cheaper source for the reflector.
William K.   6/11/2014 12:46:06 PM
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The comment about a reflector being available for a fairly high price brings to mind what I have observed locally, which is that typically the satelite system reflectors are discarded when the system is removed from an installation. While the electronic portion is recovered the reflector and mount are not. So if one is able to spot such an item the price is "free", which makes the project a lot less expensive. Of course in some states the policy may be quite different, but here in southeastern Michigan the used equipment does not get re-utilized by the company.

 

And when I first saw this posting it did look quite familiar, and then I realized that it is a re-posting of a previous post. It is a good one, certainly worthy of recycling.

Cadman-LT
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Re: Hmm
Cadman-LT   6/17/2013 6:48:38 AM
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78RPM, ok I get it. You made a quality one. I also get the microscopic function....spyware. hehe 

78RPM
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Re: Hmm
78RPM   5/18/2013 11:21:07 PM
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Yes, Cadman-LT, there are similar products you can buy. Some of them are light weight and made of plastic.  But read the customer reviews.  Poor quality in most cases, as you would expect for less than $40.  Hey, but they only address the sonic telescope.  What about that microscopic function, eh? Mount the MEMS mic in a pen.  

I had two goals for this project beyond listening to insects and distant wildlife.  I wanted to make a truly high fidelity microphone preamp and amp that could be deployed for other uses.  The quality through the Bose headphones is amazing. I really think you could use this mic and preamp in a music recording studio. Second, I wanted to encourage hobbyists and engineers to use SOIC devices in their prototypes.  I offered an introductory method in the article.  Aside from Schmartboard products, you are encouraged to solder smaller components than DIP packages for your projects.

Jerry Cogswell

Cadman-LT
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Hmm
Cadman-LT   5/17/2013 10:22:37 PM
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I thought they already had a product similar to this. Possibly the difference with this is that you can aim it at a specific location?

armorris
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Re: Great Project
armorris   5/15/2013 2:21:04 PM
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78RPM,

Thanks for your compliment. Your project requires just as much engineering savvy as any of my projects. I look forward to seeing more from you. I'm guessing that you are a retired electrical engineer like me.

The editor just gave me permission to reveal my next project. It is a "Groan Detector". A woman was referred to me whose husband was stricken with a stroke, such that he is completely paralyzed and can do nothing but groan or make an "aaaahhhh" sound when he needs help. The live-in nurse who cares for him can't always hear him when she sleeps or is away from his bedside. The woman asked me to design a device that would remotely signal the nurse, even if she is sleeping when the patient groans for help, yet reject background noise and music, including the patient's favorite radio program.

I built the device she asked for and sent it to her. She is thrilled with it. I feel that other people, especially nursing homes would find such a device useful.  

Rob Spiegel
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Blogger
Re: Great Project
Rob Spiegel   5/15/2013 1:32:39 PM
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Hey Andy, thanks for getting involved in the Gadget Freak conversation. Feel free to talk about your upcoming gadget. It certainly won't hurt to drum up some pre-publication buzz.

armorris
User Rank
Platinum
Re: Great Project
armorris   5/14/2013 6:31:01 PM
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Hi 78RPM,

It's good to hear from you again and put a face and a name to the handle "78RPM". I might try playing around with those MEMS microphones. I have another Gadget Freak project on the way. It's been submitted for a while and may be the next one. Coincidentally, my next GF article uses a noise-cancelling electret microphone. I don't know if the editor would want me to reveal it before it's published. Yours is a nice project. Keep up the good work.

78RPM
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Re: Great Project
78RPM   5/14/2013 5:38:05 PM
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Hi, armoris, I look forward to another Gadget Freak project from you. There's a lot of good engineering savy there.  I had two grade school friends who liked to play with my dad's Wollensak tape recorder.  They both became radio DJs.

You're correct that removing the pole mount greatly reduces the weight. I didn't have trouble holding just the reflector but a cameraman is busy enough with running the camera action. If he doesn't have a sound person he will want a tripod -- one sturdy enough to hold the reflector in wind. That's a lot of equipment for one person if you are hiking into remote areas so you will need an assistant.  It would be interesting if someone who reads application notes would arrange a few MEMS mics in an array to achieve high directionality. They would need to make a custom circuit board but the reflector could be a fraction of the size.

Another idea would be to mount the mic in a pen barrel and use it to find mechanical noise like squeaks. These MEMS mics have been used to monitor the condition of bearings.

armorris
User Rank
Platinum
Re: Great Project
armorris   5/14/2013 2:05:30 PM
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When I was a teenager in the 60's, my neighbor, who was an electrical engineer and a ham, built a parabolic microphone using a small surplus radar antenna. He loaned it to me for a while and I had a lot of fun with it. I put a crystal microphone on it, connected to my toy reel-to-reel tape recorder and I could hear and record whispers from a couple hundred feet away. I imagine a satellite dish, although easily available, would be pretty heavy. I have one in my junk bin from when I upgraded to HDTV. It's too heavy for me to hold in my hand for very long. I would use a tripod for such an antenna. Removing the pole mount would reduce the weight some.

Great project, though.

William K.
User Rank
Platinum
The audio microscope.
William K.   5/12/2013 7:34:21 PM
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Not only is this a great project, with an excellent recording and a multitude of other uses, but also, this is one of the few gadget freak things that has worked for me. I have played with sensitive microphones and the usual challenge is background noise, which this system doesn't seem to have, at least not on that recording. Now I need to build one for myself. And yes, those sattelite dishes are available as discards almost every week, if one keeps their eyes open and pays attention.

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