Push to toggle mute circuit for Amazon Echo microphone

Thread Starter

SoundBlaster

Joined Jul 19, 2017
3
I found that the mute button of my Amazon Echo is handled in software, this can be easily overridden by malware:
http://blog.trendmicro.com/trendlab...an-silently-record-your-audio-video-and-more/
So you could manipulate it in such a way that when you push the mute button it actually starts to record the full conversation. Would it be so costly in hardware that Amazon took the risk to invade privacy by choosing a software method of muting?

There is enough space in the Echo to add additional components so thought of modding it by hooking the existing push button and LED to a separate hardware mute circuit using the 3V of the board. I have searched the internet and these forums but could not find a suitable design. Who can help me to find a good solution?

Screen Shot 2017-07-18 at 11.15.38 .png
 
Last edited:

AnalogKid

Joined Aug 1, 2013
8,705
Completely dead kill mute the audio, or just attenuate it a lot? 3 V is not a lot when it comes to fully enhancing a small signal MOSFET like a 2N7000 placed directly across the microphone, maybe with a small build-out resistor. It is more than enough for a small bipolar like a 2N4401, but the signal attenuation will be asymmetrical - the negative half cycles won't be attenuated as much as the positive half cycles.

ak
 

Thread Starter

SoundBlaster

Joined Jul 19, 2017
3
Welcome to AAC!
Do you have room for an alternate action DPDT switch? You don't need double throw, but I didn't see any single throw variants.
Thanks but I would like it to keep it internally, not hacking an extra switch on it.

Completely dead kill mute the audio, or just attenuate it a lot?
The whole purpose is that no sound can be recorded if muted, so it is good enough if it is attenuated under the level which the ADC can sample.

Will one of these solutions work?
https://electronics.stackexchange.com/questions/4060/make-a-momentary-switch-control-a-toggle
 

AnalogKid

Joined Aug 1, 2013
8,705
The first three schematics are all variations on the same theme, and what I had in mind. Also, you can replace the two inverters with two transistors if you don't want a half-used 14 pin package in the works. 1/2 of a CD4013 does the same thing, but again there is the space of a half-used chip. A 3.3 V battery might be a bit low for a 2N7000/7002. Whatever the toggle circuit is, you need an additional element to mute the audio. With luck this is three MOSFETs plus some Rs and Cs.

ak
 
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