Turtle Art sensor xo 1.75 range voltage

[Frederick Grose]

On Sat, Jun 2, 2012 at 12:59 AM, John Watlington <wad at laptop.org> wrote:

>
> On Jun 1, 2012, at 9:24 PM, forster at ozonline.com.au wrote:
>
> >> We should test the calibration again.
> > Walter, Guzman
> >
> > Testing with TA140
> >
> > It looks like the 1.75 audio circuit was changed between the
> preproduction and the ramp unit 1.75's
> >
> > Testing on SKU199 and SKU204, the impedance has gone from 1k to 4k and
> the calibration is all wrong on 204
> >
> > (TA calibration should be OK for the moment on preproduction SKU199)
> >
> > Can laptop.org please confirm that there was an audio redesign between
> SKU199 and SKU204? Is the SKU204 design now stable or can we expect further
> changes?
>
> Yes, there was a redesign which increased the resistance between the Mic
> voltage source and the mic jack
> from roughly 1K to roughly 3K for improved microphone performance.    All
> production XO-1.75s use the SKU204 circuitry.
>

See
http://wiki.laptop.org/go/XO1.75_B1_C1_Changes


>
> > Is the input protection the same as the 1.5: "The XO-1.5 is protected by
> a resistor,(1/16W 470 ohm SMD0402) and a pair of diodes to ground and to
> +3.3V which should protect -6V to +9V continuously, and up to higher
> voltages for shorter periods of time."
> http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors#Specifications
>
> Yes, the protection circuitry is the same as used on 1.5.
>
> Chers,
> wad
>
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