555 Oscillator and Running Lights - doc00020
This is a demo of the standard LED running lights that many know
of, the only thing different is that you can try out the project
The 555 clocks 4017 counter and it counts and Ten LEDs indicate
the counts. This can be used as a Sequential timer or for
generating staircase waveform.
Press the Red button below to turn on the circuit press it again
to turn off, i have put a new battery and did the wiring for
you. The Red LED will flash according to the state of the 555
output at pin 3. The decade counter-divider CD4017 has 10
outputs, for every low to high transition, rising edge, the
counter advances one LED. After going one full circle the the
first LED lights again and it goes on.....
You can vary the value of R2 using the controls below to
make LEDs run fast or slow. The frequency of oscillation of
astable 555 is given as f = 1.44 / ((R4 + 2 * (R2 +
R3)) * C3).
The 10 outputs have 10 green LEDs. The current thru the
LED is limited by R1, the current can be calculated like this
(9V - 1.6V) / 1K = 7.4mA this is within 20mA which is the
danger limit of the CMOS output. You want it to be bright use
transistors for every output.
The cap C1 is a filter and C2 is to prevent noise at pin 5
influencing the output as it is a control voltage point.
You can cascade or chain many more counters with the CO or carry
out pin 12 of 4017. The pin 15 reset is kept at low for
counting, on high it will reset the counter but is not used in
(i created some confusion with this sentence and i got muddled
up myself when answering some email from youngsters, as these
were things i did when i was a kid. Cascade means in
mathematical sense not in the "Bike Lights" sense. So when you
cascade - the first set of ten is "Units", the next stage is
"Tens" the next is "Hundreds" ... It becomes a Non-7-Segment Led
number display. The "Bike Lights" of greater than 10 LEDs can be
done with shift registers...)
555 Oscillator and Decade Counter xml
use iframe part for
your Webpage or Blog.
the above circuit in pdf format del00017.pdf
the cadsoft eagle source of the circuit del00017.zip
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