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Activities/Turtle Art/Using Turtle Art Sensors (view source)
Revision as of 19:26, 6 November 2010
, 19:26, 6 November 2010no edit summary
The OLPC XO can measure external inputs with its microphone jack
The OLPC XO can measure external inputs with its microphone jack
Specifications
==Specifications==
Standard 3.5mm 2-pin switched mono microphone jack; selectable 2V DC bias; selectable sensor-input mode (DC or AC coupled)
Standard 3.5mm 2-pin switched mono microphone jack; selectable 2V DC bias; selectable sensor-input mode (DC or AC coupled)
If using a stereo plug it is the red wire plus the earth.
If using a stereo plug it is the red wire plus the earth.
It is protected at the input by a 5V zener diode and has a measurement range of 0.3V to 1.9V. The allowable input is -0.5V to 5V Inputs outside this range will cause excessive current and damage.
It is protected at the input by a 5V zener diode and has a measurement range of 0.4V to 1.85V. The allowable input is -0.5V to 5V. Inputs outside this range will cause excessive current and damage.
Addition of a 150k ohm series resistor would (I expect, no guarantee) give a reduced sensitivity in voltage mode (0-4V) but allow inputs to +- 100V without damage. Input impedance in resistance, volume and pitch modes is much lower but a 1k ohm series resistor should still allow inputs to +-12V.
Addition of a 150k ohm series resistor would (I expect, no guarantee) give a reduced sensitivity in voltage mode (0-4V) but allow inputs to +- 100V without damage. Input impedance in resistance, volume and pitch modes is much lower but a 1k ohm series resistor should still allow inputs to +-12V. If applying an external voltage, it is highly recommended that test leads be made up with a mictophone plug and a series resistor.
==Voltage Mode==
Measurement range is DC 0.4V to 1.85V. Voltages less than 0.4V report as 0.4V, voltages greater than 1.85V report as 1.85V. Accuracy is around 3% of full scale.
==Resistance Mode==
Measurement range is 750 ohms to 16k ohms, resistances less than 750 ohms report as 750 ohms, greater than 16k ohms. Accuracy is around 5% with respect to the voltage measured accross the resistor, this translates to round 50 ohms at bottom scale and 2k ohms at top scale.
==Pitch Mode==
Pitch Mode is set up for the internal microphone but can be accessed through the microphone jack. 2V DC bias is on, AC coupled, +20dB boost is on. The resolution is +-8Hz