Re: Voice annunciated test box circuitry

From: Robert Monsen (rcsurname_at_comcast.net)
Date: 02/18/05 

Date: Thu, 17 Feb 2005 21:58:35 -0800

mirach wrote:
> Thanks guys for the great responses . I could actually get by at
> present with 128 individual numbers. (we currently arnt working on the
> units with 256 wires). Some of the involved electronics is beyond my
> scope of knowlege, so im not against paying someone to put a couple of
> these together if a price could be worked out that we both could live
> with. I could even send you the empty boxes probably 8"Wide by 6"
> high by 2" deep. and they would probably be assembled without the plug
> (we can wire the actual plugs) so basically its making the boards and
> chips work then I can take it from there. I like the idea of a portable
> device ,this is the way our current light boxes are and it would be a
> plus to be portable. I had originally wondered if you might be able to
> get 128 small cheap 1 or 2 second voice chips that could each be
> triggered by a voltage when that wire is touched . But I may be
> dreaming on that one :) . I was originally thinking of these chips
> replacing the LEDs currently in the boxes. That may be too simplistic
> of an idea since im not sure whats avialiable. Let me know what you
> think guys. And again Thank You
>

The voice chips are fairly expensive, so I think getting a slew of them
won't be practical.

I spent some time attempting to redeem myself by coming up with a simple
way to input your 256 signals.

One simple way would be to use a 16x16 grid of NPN transistors, arranged
in rows and columns. The collectors of all the transistors in a
particular row would be wired together. All of the bases in a column
would be connected together, in such a way that all the bases in a
column could be driven by raising a single pin for that column.

The plug pin you want to identify is then grounded. The others are left
to float.

Now, by powering the columns one by one (through a 1k resistor), you can
find the grounded plug pin by noticing which row goes to 0, using the
column number as the low address byte, and the row number as the high
address byte. If no emitter is grounded, the row will be near logic 1
due to the diode action of the collector.

You can walk through the rows by asserting them one at a time, and then
reading the result with a microcontroller. Once you find the row that is
low, you know the row and column address, and can thus tell the voice
chip which digits to say.

The voice chip will be expensive to run in terms of power, particularly
if you want volume. However, using an earplug would make it a lower
power device, thus allowing for the ability to carry it around.

How big are the plugs? 

-- 
Regards,
   Robert Monsen
"Your Highness, I have no need of this hypothesis."
     - Pierre Laplace (1749-1827), to Napoleon,
        on why his works on celestial mechanics make no mention of God.

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