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FUNCTION BLOCK
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DESCRIPTION
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- This circuit will count input pulses and output the number in binary.
- It is very useful for creating long timing periods.
- Also used to divide astable frequencies.
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CIRCUIT DETAILS
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There are 3 binary counters shown below. The only difference between them is the number they can count up to. These types are very simple and are known as ripple counters.
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Inputs
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Circuit Diagram, 7 stage
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- Clock - A low pulse on this input increments the sequence
- Reset - A high input will reset the counter to zero.
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Outputs
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7-stage binary counter (4024B)
The outputs Q1-Q7 carry the binary count from:
Binary = 000 0000 to 111 1111
Decimal = 0 to 127
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12-stage binary counter (4040B)
The outputs Q1-Q12 carry the binary count from:
Binary = 0000 0000 0000 to 1111 1111 1111
Decimal = 0 to 4095
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Circuit Diagram, 12 stage
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14-stage binary counter (4020B)
The outputs Q1-Q14 carry the binary count from:
Binary = 00 0000 0000 0000 to 11 1111 1111 1111
Decimal = 0 to 16383
(Note: Q2 and Q3 are not available outputs)
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Circuit Diagram, 14 stage
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CREATING TIMING CIRCUITS
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By connecting an astable to the clock input of a fixed frequency, the counter outputs can be used as timed outputs. For example, if an astable of 1 Hz is connected to the clock, then the outputs will go high after the following number of 1 second pulses:
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Q1 = 1 pulse
Q2 = 2 pulses
Q3 = 4 pulses
Q4 = 8 pulses.
Q5 = 16 pulse |
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Q6 = 32 pulses
Q7 = 64 pulses, (1 min approx)
Q8 = 128 pulses, (2 mins)
Q9 = 256 pulses, (4 mins)
Q10 = 512 pulses, (8 mins) |
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Q11 = 1024 pulses, (16 mins)
Q12 = 2048 pulses, (32 mins)
Q13 = 4096 pulses, (1 hour approx)
Q14 = 8192 pulses, (2 hours) |
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By adjusting the clock frequency, you can obtain longer and shorter delays, and by cascading them, (joining 2 counters in series with the last output from the first counter connected to the clock of the second) gain delays of days, weeks or even months.
Connect a driver and an output device to one of the outputs so it activates when that output goes high.
For Q7 to equal exactly 1 min, clock frequency = 1.067Hz
For Q11 to equal exactly 1 hour, clock frquency = 1.138Hz.
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PACKAGE DETAILS
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The counter packages and connections are shown below
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IMPORTANT: Try not to handle the pins of the IC too much. They do have protection diodes connected inside but CMOS types are very sensitive to static charge. |
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If possible use an IC holder so the IC can be removed easily and is not damaged from excessive heat while soldering. |
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LINKS
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Links to circuits using binary counters
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| Written by Phil Townshend - 2008 |
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www.edutek.ltd.uk - Working Electronics For Students & Teachers
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