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Line 11: − If using a stereo plug it is the tip (usually the red wire) plus the earth.+ − + − + − + Line 25:
Line 25: − + − + − 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. Impedance 140k ohms to a 0.6V bias.+ − + − + + + + + + + + + − + − Measurement range is 750 ohms to 14k ohms, resistances less than 700 ohms report as 700 ohms, greater than 14k ohms report as 14k ohms. Accuracy is around 5% with respect to the full scale voltage measured across the resistor, this translates to round 50 ohms at bottom scale and 2k ohms at top scale. (A series protection resistor of around 700 ohms would give a measurement range of 0 - 13k ohms and protection against +-8V inputs.)+ + + + − + − 2k ohms to open circuit. (Still buggy, click stop to clear bug.)+ + + + Line 420:
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Activities/Turtle Art/Using Turtle Art Sensors (view source)
Revision as of 03:58, 21 November 2013
, 03:58, 21 November 2013→XO-1.75
Standard 3.5mm 2-pin switched mono microphone jack; selectable 2V DC bias; selectable sensor-input mode (DC or AC coupled); selectable +20dB boost.
Standard 3.5mm 2-pin switched mono microphone jack; selectable 2V DC bias; selectable sensor-input mode (DC or AC coupled); selectable +20dB boost.
On the XO-1, mono data is measured, the left channel, the tip (usually the red wire). The XO-1.5, XO-1.75, XO-3 and XO-4 can read both the left and right channel. (Currently on the XO-1.75, XO-3 and XO-4 stereo input is disabled).
The XO1 is protected at the input by a 5V zener diode. The allowable input is -0.5V to 5V. Inputs outside this range will cause excessive current and damage. Even a single 1.5V battery can cause damage if connected reverse polarity.
The XO-1 is protected at the input by a 5V zener diode. ([http://wiki.laptop.org/go/File:XO-1_Schematics.pdf 1]) The allowable input is -0.5V to 5V. Inputs outside this range will cause excessive current and damage. Even a single 1.5V battery can cause damage if connected reverse polarity.
The XO1.5 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. Similar protection is planned for the XO1.75.
The XO-1.5 ( [http://wiki.laptop.org/go/File:XO-1.5_Schematics_rev_G.pdf 2] [http://wiki.laptop.org/go/File:XO-1.5_Schematics_rev_I.pdf 3] [http://wiki.laptop.org/go/File:XO-1.5_Schematics_rev_M.pdf 4] )and XO-1.75 (XO-3 and XO-4 presumably too) are 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.
For the XO1, the 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.
For the XO-1, the 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.
<b>If applying an external voltage to the XO1, it is highly recommended that test leads be made up with a microphone plug and an inbuilt series resistor. 680 ohms is the suggested resistor value, it gives a reasonable input range while still allowing the use of the full resistance range of the XO1.</b>
<b>If applying an external voltage to the XO1, it is highly recommended that test leads be made up with a microphone plug and an inbuilt series resistor. 680 ohms is the suggested resistor value, it gives a reasonable input range while still allowing the use of the full resistance range of the XO1.</b>
<i> 680 ohm series resistor on a 3.5mm audio plug</i>
<i> 680 ohm series resistor on a 3.5mm audio plug</i>
Test leads with a zener diode and series resistor would expand the safe range for the XO1.5 and XO1.75.
Test leads with a zener diode and series resistor would expand the safe range for the XO1.5, XO1.75, XO-3 and XO-4.
Damage can also be caused by applying voltages between the grounds of any of the external sockets.
Damage can also be caused by applying voltages between the grounds of any of the external sockets.
==Voltage Mode==
==Voltage Mode==
===XO1===
===XO-1===
One channel, 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. Impedance 140k ohms to a 0.6V bias.
[[File:Voltage sensor.jpg]]
[[File:Voltage sensor.jpg]]
===XO1.5===
===XO-1.5===
0.17V - 3.0V, impedance 15k ohms to a 1.7V bias. (Still buggy, click stop to clear bug.)
Two channels, 0.17V - 3.0V, impedance 15k ohms to a 1.7V bias. (Still buggy, click stop to clear bug.)
===XO-1.75===
Two channels, -0.3V to 3V, input impedance 4k ohms to a 3V bias, (models SKU204+ *) . At the time of writing, as a workaround to a bug with dual channels, apply the input to both channels, only a mono reading is available.
(* A small number of pre-production laptops were built with -3V to +3V input range and input impedance 1k ohm to a +3V bias, eg. model SKU199. Turtle Blocks V141 and previous is correctly calibrated for these laptops but not for production laptops)
===XO-4===
Two channels, 0 to 3V. At the time of writing, as a workaround to a bug with dual channels, apply the input to both channels, only a mono reading is available.
==Resistance Mode==
==Resistance Mode==
===XO1===
===XO-1===
One channel, measurement range is 750 ohms to 14k ohms, resistances less than 700 ohms report as 700 ohms, greater than 14k ohms report as 14k ohms. Accuracy is around 5% with respect to the full scale voltage measured across the resistor, this translates to round 50 ohms at bottom scale and 2k ohms at top scale. (A series protection resistor of around 700 ohms would give a measurement range of 0 - 13k ohms and protection against +-8V inputs.)
===XO-1.5===
Two channels, 2k ohms to open circuit. (Still buggy, click stop to clear bug.)
===XO1.5===
===XO-1.75===
Two channels, zero ohms to open circuit. At the time of writing, as a workaround to a bug with dual channels, apply the input to both channels, only a mono reading is available.
===XO-4===
Two channels, zero ohms to open circuit. At the time of writing, as a workaround to a bug with dual channels, apply the input to both channels, only a mono reading is available.
==Pitch Mode==
==Pitch Mode==
== RC time constant ==
== RC time constant ==
IT IS RECOMMENDED THAT A SERIES PROTECTION RESISTOR BE BUILT INTO THE PHONO PLUG AND LEADS IF USING AN EXTERNAL VOLTAGE
IT IS RECOMMENDED THAT A SERIES PROTECTION RESISTOR BE BUILT INTO THE PHONO PLUG AND LEADS IF USING AN EXTERNAL VOLTAGE WITH THE XO-1
[[File:Rc cct.jpg]]
[[File:Rc cct.jpg]]
R = T/C
R = T/C
= 0.14 /(4x10^-6) = 35k
= 0.14 /(4x10^-6) = 35k
[[File:Rc-time.jpg]]
[[File:Rc-time.jpg]]
[[File:RC data to clip.jpg]]
[[File:RC data to clip.jpg]]
See also a similar experiment which uses the [[Activities/TurtleBots#Buti.C3.A1|USB4Butia]] board (in Spanish) http://youtu.be/eewFtOHX5-Q and http://youtu.be/KmNwC1qBhtA
==Voltage-current relationship==
Some devices including light bulbs have non-linear voltage current relationships. In this experiment, the V-I graph of a light bulb is drawn using the stereo input of the XO-1.5.
[[Image:VIgraph.jpg|250px]] [[Image:VI Turtle Art.png|400px]]
[[File:Turtle Art Activity VI.ta]]
The light bulb and resistor were chosen thus. The maximum measurable input of the XO-1.5 is +3V, at maximum you want approximately 1.5V across the resistor and 1.5V across the bulb, the bulb should be near full brightness. A 2.8V 0.85A torch/flashlight bulb was used. The estimated resistance of the bulb is V/I, 2.8V/0.85A = 3.3 ohms, chosing from resistors at hand, trial and error found 2.2 ohms was OK. The power rating of the resistor is V*V/R, 1.5*1.5/2.2 = 1.02W, a resistor of 1W or higher rating is required.
A laboratory power supply was used in this experiment. It is safest if its output is within the maximum allowable voltage range of the XO-1.5, -6 to +9V. Low cost options would include a selection of dry cells in varying states of discharge. It may be practical to construct a variable resistor using a pencil lead.
The X axis is voltage across the bulb, voltage2 - voltage, the Y axis is the current which is proportional to the voltage across the resistor or the L channel voltage.
See also http://youtu.be/37vJEUr5nRI and http://www.youtube.com/watch?v=_iSXHsGvLaY (in Spanish) for experiments plotting linear and nonlinear V-I relationships using the [[Activities/TurtleBots#Buti.C3.A1|USB4Butia]] board.
==The XO as an audio amplifier==
==The XO as an audio amplifier==
[[File:Beatfrequency.jpg]]
[[File:Beatfrequency.jpg]]
===Wavelength and the speed of sound===
Measure the wavelength and hence the speed of sound using 2 OLPC XO laptops, one runs Turtle Art the other Measure, inspired by http://www.ted.com/talks/lang/en/clifford_stoll_on_everything.html
http://www.youtube.com/embed/l3vKVTW1LQA
One laptop running Turtleart is used to generate a 3kHz audio tone. The second laptop, XO-1.5 or higher, graphs the output of 2 microphones with Measure. If the 2 microphones are at equal distance from the source then the 2 traces are in phase. Move one microphone by half a wavelength and the 2 traces are opposite phase.
This experiment is best with a XO-1.5 or higher with stereo input. If you only have a mono XO-1 then you could parallel the 2 microphones to the mono input and see how the amplitude of the summed signal changes as you move one microphone
===Gliding tone===
===Gliding tone===
Move the wire loop along the wavy wire but do not make contact.
Move the wire loop along the wavy wire but do not make contact.
The "Turtle Blocks" program monitors the resistance at the microphone input. To start playing, touch the wire with the ring once. Thereafter the program displays alerts every time you touch again. On reaching the opposite end of the wire, press the switch button and the program shows the player and resets for a new game.
[[File:Steady hand game.jpg]]
[[File:Steady hand game.jpg]]