Subject:
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Re: Light sensor initialization time?
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Newsgroups:
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lugnet.robotics.rcx.java
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Date:
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Thu, 27 Sep 2001 20:52:56 GMT
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Viewed:
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2836 times
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I suspect this is due to the fact that the first
sample from the sensor is actually being obtained
while the sensor's reservoir capacitor is still charging.
Why don't you try a simple test, actually two tests;
1.
Initialise as passive sensor
Wait 1 second
Run your code
2.
Initialise as active sensor
Wait 1 second
Run your code
You may find that the results will differ
because the sensor has already settled down
in the second case, but will still be charging
in the first case.
JB
In lugnet.robotics.rcx.java, Martin Egholm Nielsen writes:
> Hellow!
>
> Here a little fact: the first reading on the light sensor
> _just_ after you have activated it is too high. It seems
> like one has to wait a little after activating the sensor.
> The following program shows it rather nicely:
> ____START OF CODE____
> import josx.platform.rcx.*;
>
> public final class WeirdLight implements SensorConstants {
>
> public static void main( String[] args ) {
> Sensor.S2.setTypeAndMode( SENSOR_TYPE_LIGHT,
> SENSOR_MODE_PCT );
> Sensor.S2.activate();
>
> // Uncomment the following to make it behave as expected
> //try { Thread.sleep( 500 ); } catch ( Exception e ) {}
>
> int val = Sensor.S2.readValue();
>
> LCD.showNumber( val );
> try { Thread.sleep( 1500 ); } catch ( Exception e ) {}
>
> Sensor.S2.passivate();
> } // main
> } // WeirdLight
> ____END OF CODE____
>
> If you include the first sleep command the value is as
> expected.
> When I ran the program I got the following results: 79-80
> _without_ the sleep, and 33-35 (black tape) with the sleep.
>
> Regards,
> Martin E. Nielsen
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Message is in Reply To:
 | | Light sensor initialization time?
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| Hellow! Here a little fact: the first reading on the light sensor _just_ after you have activated it is too high. It seems like one has to wait a little after activating the sensor. The following program shows it rather nicely: ____START OF CODE____ (...) (23 years ago, 27-Sep-01, to lugnet.robotics.rcx.java)
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