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PDA 05 5/30/03 11:35 AM Page 105
Figure 5.50
Average distance Chapter 5 / The Electronics
versus voltage.

must be determined. The voltage levels representing distance will
vary slightly from unit to unit. A small survey of randomly selected
devices was conducted and data gathered are shown in Figure 5.50.
The columns Distance and Average Voltage in the sample data pro-
vided can be used as a look-up table.

Using the average of the voltage measurements for the four samples,
the following graph was produced. The data points indicate the aver-
age values, and the line shows the best fit equation calculated.
The equation derived that best fits the average voltages is given as:
Distance (cm) 27 (Voltage) 1.1. This equation can be used for
calculating the distance to an object by simply entering the voltage
measured and calculating the distance in centimeters. The preceding
formula is provided for reference only; while it is shown to be quite
accurate, part-to-part variation must be considered.

Ambient Light

Tests have shown the GP2D12 to be highly immune to ambient light lev-
els. Incandescent, fluorescent, and natural light do not appear to bother
it. The only instance where we were able to get it to falsely measure was
when a flashlight was pointed directly into the sensor’s receiver; even a
few degrees off center is enough for the sensor to ignore it.

IR Light
The GP2D12 uses a modulated IR beam to guard against false trigger-
ing from the IR component of incandescent, fluorescent, and natural
light. Tests with several kinds of IR remote controls have shown that
even with two or three remotes pointed at the GP2D12, the unit still
functions normally.

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