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Les langues disponibles
Les langues disponibles
Optics
Fibroptonic
Ref : 202 012
1 Purpose
To detect a variation in the light intensity using a photoresistor.
2 Precautions for use
The resistance of the photoresistor reduces when it is illuminated. In sunlight, the
resistance is a dozen ohms; in darkness the resistance can exceed thousands of ohms.
The photoresistor R is installed in series with the potentiometer RV of 2.2 kilo ohms and a
resistance R0 of several hundred ohms. If U is the supply voltage on the terminals of the
assembly, the electrical power for the photoresistor is:
This power is maximum for RV = 0 and R = R0 thus Pmax = U^2/4 R0. As the maximum
power indicated by the manufacturer is 0.3 watts, we deduce that U must be less than (1.2
R0)^1/2 that is 12 V for R0 = 120 ohms.
3 Light
This part can be the subject of experiment sessions. The experiments suggested are easy
to implement and not very common; the results are immediate.
This part can be the subject of experiment sessions. The experiments suggested are easy
to implement and not very common; the results are immediate.
ENGLISH
FIBROPTONIC
sources
periodically. Measurement of periods
3.1 Equipment:
•
Photoresistor module
•
6, 9 or 12 V DC power supply
•
Oscilloscope
•
40 or 60 W light bulb operating on 220 V mains supply
•
Pocket torch (battery powered)
•
Neon indicator (stair opening type) operating on mains supply
•
Fluorescent tube light (classroom lighting, for example)
•
Mechanical stroboscope or a DC motor fitted with a cardboard disk pierced with
holes or slits.
or cinecolor Part no. 201 019
3.2 Set-up:
•
Power the photoresistor with 6 or 9 V DC between the 2 black and green outer
terminals. The 3 elements of the module being symmetrical dipoles, the connecting
DETECTION OF VARIATIONS IN
LIGHTING
whose
brightness
60
SHEET
08
varies
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