Data Sheet

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372. Siren Fading In and Out
Build the circuit to the left, turn on the switch (62), and you will hear a
low volume siren with the heart LED (69) and colorful LED (72) ashing.
Listen as the colors change on the colorful LED (72). Can you detect a
pattern? Turn off the switch (62) and the siren and LEDs will go off. In
this circuit you may have noticed that the siren fades out as the colorful
LED (72) turns green and blue but then the siren comes back when the
LED turns red. As discussed in project #97, green and blue light have
higher turn on voltages than red light. So when the colorful LED (72)
is red, there is just enough voltage left for the 3-in-1 (11) to function
correctly, but when the colorful LED (72) turns green and blue, there is
not enough voltage left for the 3-in-1 (11) to function.
373. Changing Voltage
Connect points C and D with the 100W resistor (41) in project #372.
Turn on the switch (62) and you will hear low volume gun shots and
machine gun sounds with the heart LED (69) and colorful LED (72)
ashing. Listen as the colors change on the colorful LED (72). Turn off
the switch (62) and the sounds will go off. If you had a voltmeter and
measured across the points D3 and D6 in this circuit, you would see
that there is about 2.7V powering the 3-in-1 (11) when the colorful
LED (72) is red, but only about 2.3V powering the 3-in-1 (11) when the
colorful LED (72) is green or blue. As discussed in the previous project,
2.7V is enough to enable the 3-in-1 (11) to function properly, but 2.3V
is not enough.
374. Changing Current
Connect points A and B with the 4-wire (4) in project #372. Turn on the
switch (62) and you will hear a low volume re siren with the heart LED
(69) and colorful LED (72) ashing. Listen as the colors change on the
colorful LED (72). Turn off the switch (62) and the re siren will go off.
If you had an Ammeter and measured the current coming out of node
D6 towards the battery module (91) you would see that there is about
60mA of current owing through the 3-in-1 (11) when the colorful LED
(72) is red but only about 10mA when the colorful LED (72) is green or
blue. As discussed in the previous project, 60mA is enough to enable
the 3-in-1 (11) to function properly, but 10mA is not enough.
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