Elenco LIGHT - Manual (Page 73)

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Project 159 Photo Control
Project 160 Resistance Director
Set the lever on the adjustable resistor (RV) all the way towards the
press switch (S2). Turn on the slide switch (S1), and push the press
switch. The color LED (D8) will light for a while and then slowly turn off.
The brighter the light on the phototransistor (Q4), the shorter the color
LED stays on.
You can replace the color LED with the red LED (D1) or the white LED
(D6).
Move the lever on the adjustable resistor (RV)
across its range and watch the brightness of
the white and color LEDs (D6 & D8).
Replace either LED with the red LED (D1) and
compare it too.
You can also replace one of the battery
holders (B1) with a 3-snap wire, and compare
the LED brightnesses at lower voltage.
The adjustable resistor can be
adjusted from about 200 ohms to
about 50,000 ohms.
The white LED is a super-bright
LED, so will be brighter than the
others at comparable resistance.