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Activities/Turtle Art/Using Turtle Art Sensors (view source)
Revision as of 22:04, 19 December 2012
, 22:04, 19 December 2012→Voltage-current relationship
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.
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.
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.