Turtle Art sensor xo 1.75 range voltage

[John Watlington]

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.

> 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