Inexpensive Lightweight Speech Recognition

Well, the blanks did anyway. I know I could have just ordered this from a board house and been done with it, but what fun is that :) I am going to be using a toner transfer method to create the board layouts. I have not decided on which etching method I will use. In the past I have readily utilized Ferric Chloride. I am looking at other options however that may have less of an environmental impact. One possible solution is to use cupric chloride which can be reused. There is a nice article on it here http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/?ALLSTEPS

Before I jump into mixing chemicals listed on a website, I plan on talking to a friend of mine who is a chemistry professor at the University of Alaska to see what he thinks about the above solution and if it really is "more friendly".

For those who are not familiar with toner transfer PCB etching, http://www.dr-lex.be/hardware/tonertransfer.html

Those of you out there may say "why bother with all this, why not just order them?" Part of that is cost, I can etch many PCB's for a few dollars in components. The other reason is that this is a hobby and how I spend my free time. I enjoy the entire process of creating an object and much of it is about the journey. Without the journey, you don't learn. Learning is where the most enjoyment comes from.

I will get images up later after the board is etched as well as the results of the initial testing.

Cheers!

I am curious to know if a multiplexer could be used along with a set of external band pass filters could be used to create the same effect as the commonly available IC's on the market. By having each filter go high if the tones are "heard" and then stepping through them in a circular pattern with a simple looping binary counter could we create enough points that can be used to differentiate very subtle differences in the audio world around the "ear" ?

For those not familiar with band pass filters I recommend reading https://en.wikipedia.org/wiki/Band-pass_filter

For those not familiar with a Multiplexer or MUX, I recommend reading https://en.wikipedia.org/wiki/Multiplexer

The counter could be powered by either a micro-controller or you could create one using several flip flops and a clock pulse.

If you look at the above links, you can see the simplicity of this sort of system. No idea if it will work, but I am making a note here to remind myself to give it a try :)

In initial tests using a spectrum analyzer I was able to differentiate between several different sound occurrences based upon the spectrum of each of those components. I was considering the way that the chip I am using captures the audio. It occurs in such a way that it uses a round robin approach in order to scan the spectrum, each a few ns apart. This might be useful when trying to capture words directly as well as other sounds as in a word, there is definitely a progression of different tones that go together to create a recognizable phonetic.

After looking at the wiring that needs to be done, I decided that using a veroboard would be mildly annoying. In the spirit of DIY I have decided to try etching a simple double sided PCB. I took a look at the current free software offerings both in price and "in spirit" and gave several of the PCB tools out there a quick try.

Eventually I ended up using EAGLE, it simply had the parts libraries already there. I did look at several other tools including but not limited to KiCAD, Ftritzing, and Circuitmaker. They all have their ups and downs. After the board is etched and tested, I will be uploading the PCB files used.