Sunday, December 9
16-LED NIGHT RIDER
Description
The bi-directional sequencer uses a 4 bit binary up/down counter (CD4516) and two “1 of 8 line decoders"
(74HC138 or 74HCT138) to generate the popular Night Rider display. A Schmitt Trigger oscillator provides the
clock signal for the counter and the rate can be adjusted with the 500k pot. Two additional Schmitt Trigger
inverters are used as a SET/RESET latch to control the counting direction (up or down). Be sure to use the
74HC14 and not the 74HCT14, the 74HCT14 may not work due to the low TTL input trigger level. When the
highest count is reached (1111) the low output at pin 7 sets the latch so that the UP/DOWN input to the counter
goes low and causes the counter to begin decrementing. When the lowest count is reached (0000) the latch is reset (high) so
that the counter will begin incrementing on the next rising clock edge. The three lowest counter bits (Q0, Q1, Q2) are
connected to both decoders in parallel and the highest bit Q3 is used to select the appropriate decoder.
to Index
555 SCHMITT
Circuit Diagram
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