Do only 4 of those 10 outputs (Q0-Q9)contain the numerical information
Of course. It's just that it only counts up to four bits worth. The
There are a lot of different ways to count to 16 -- it's just that four
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This is what I'm seeing:
So, the 4017 is a bcd decade counter. But it has a decoder that decodes
Yes.
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There is no "bcd" (binary coded decimal) involved in the 4017. It's a
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What has slowed me down a bit is a sort of assumption I've had aboutOn Thu, 30 Jun 2011 20:59:21 +0100, Richard<none@ntlworld.com> wrote:
On 30/06/2011 20:08, Michael Black wrote:
On Thu, 30 Jun 2011, Richard wrote:
Well, I thought I'd better read the MC14017B notes. :c)
It says: " The ten decoded outputs are normally low, and go high only
at the appropriate decimal time period".
I've little idea how this explains how the counter is used to display
a count with (say) 7 segment LED displays.
It isn't, you're using the wrong device.
The 4017 would work if for each digit you had 10 LEDs, labelled 0-9.
ONly one LED would go on, to indicate the count between 0 and 9. Once
upon a time, the readouts were like that, Nixie tubes that 10 distinct
numbers in an envelope, and a BCD decoder would turn the BCD into one of
ten distinct outputs to turn on the needed digit.
The 4017 is a bcd decade counter and a bcd to "1of10" decoder in the
same pacakge. Since it doesn't output BCD, it won't work for thise project.
7 segment readouts don't work that way. There are 7 segments, but for
each number you have to turn on a number of those segments. Hence there
are BCD to 7segment decoders, which take the BCD code and turns it into
the outputs that will turn on the needed segments to display the
matching number on the 7segment readout.
These are not the same thing. If you want to drive a 7segment readout,
you need a bcd output counter, then a bcd to 7segment decoder. The 4017
is useful as a simple decade counter, and for things where you need an
distinct indicator for each of the distinct digits 0-9. There are lots
of uses for that.
There are lots of bcd counters that will do what you need, and I assume
one can still get BCD to 7segement decoders.
Once upon a time, these things were common enough that one could find
devices that had the counter, decoder and even a latch between the two
in a single package, one company even put it in the same package as the
readout. But they were expensive.
Michael
So, the 4017 is a bcd decade counter. But it has a decoder that decodes
the bcd, such that only one of the 10 outputs is hot at any given moment
or time.
As the count progresses, each clock step leads to the next output going
hot. So, in 10 pulses, every output has been hot at some time, and the
cycle repeats. In theory then, to make one Johnson decade counter IC
control a single 7 segment LED, you would need a further decoder that
assigns the appropriate series of LEDS that are to be turned on, for
each of the 10 inputs possible. But, that is just not done. The 4017
was not envisioned to run 7 segment LED displays. Will run a nixie tube
though with suitable driver.
That's what I understand at this point.
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You got it!
It could be viewed as a 4 bit counter followed by a BCD-to-decimal decoder.
AAMOF: you can not! You have 4 outputs outputting BCD and your 7-segment
1) a 7-segment display has 7 inputs (one for each segment) while the
A traditional approach for a counter/decoder setup withOn 30/06/2011 22:03, John Fields wrote:
On Thu, 30 Jun 2011 20:59:21 +0100, Richard<none@ntlworld.com> wrote:
On 30/06/2011 20:08, Michael Black wrote:
On Thu, 30 Jun 2011, Richard wrote:
Well, I thought I'd better read the MC14017B notes. :c)
It says: " The ten decoded outputs are normally low, and go high only
at the appropriate decimal time period".
I've little idea how this explains how the counter is used to display
a count with (say) 7 segment LED displays.
It isn't, you're using the wrong device.
The 4017 would work if for each digit you had 10 LEDs, labelled 0-9.
ONly one LED would go on, to indicate the count between 0 and 9. Once
upon a time, the readouts were like that, Nixie tubes that 10 distinct
numbers in an envelope, and a BCD decoder would turn the BCD into one of
ten distinct outputs to turn on the needed digit.
The 4017 is a bcd decade counter and a bcd to "1of10" decoder in the
same pacakge. Since it doesn't output BCD, it won't work for thise project.
7 segment readouts don't work that way. There are 7 segments, but for
each number you have to turn on a number of those segments. Hence there
are BCD to 7segment decoders, which take the BCD code and turns it into
the outputs that will turn on the needed segments to display the
matching number on the 7segment readout.
These are not the same thing. If you want to drive a 7segment readout,
you need a bcd output counter, then a bcd to 7segment decoder. The 4017
is useful as a simple decade counter, and for things where you need an
distinct indicator for each of the distinct digits 0-9. There are lots
of uses for that.
There are lots of bcd counters that will do what you need, and I assume
one can still get BCD to 7segement decoders.
Once upon a time, these things were common enough that one could find
devices that had the counter, decoder and even a latch between the two
in a single package, one company even put it in the same package as the
readout. But they were expensive.
Michael
So, the 4017 is a bcd decade counter. But it has a decoder that decodes
the bcd, such that only one of the 10 outputs is hot at any given moment
or time.
As the count progresses, each clock step leads to the next output going
hot. So, in 10 pulses, every output has been hot at some time, and the
cycle repeats. In theory then, to make one Johnson decade counter IC
control a single 7 segment LED, you would need a further decoder that
assigns the appropriate series of LEDS that are to be turned on, for
each of the 10 inputs possible. But, that is just not done. The 4017
was not envisioned to run 7 segment LED displays. Will run a nixie tube
though with suitable driver.
That's what I understand at this point.
---
You got it!
What has slowed me down a bit is a sort of assumption I've had about
counters. I've been thinking that a counter is a counter is a counter.
When in fact you cannot just select any counter for your needs. When I
say mixing oranges and apples, this is what I am referring to. You do
that when you try to treat all counters the same. When seeking to use 7
segment LED displays not all counters have outputs that are suitable.
The 4017 is not suitable, because although it is a decade counter it's
outputs are "1in10" type and there is no "1in10" to 7 segment LED
decoder available. If there was it could be a substitute for a counter
whose outputs are BCD. People mentioned that, but when starting out
things sometimes just pass you by.
I don't think there is any BCD in the 4017 because it's a ring counter.
So, whatever decoder that is in that IC, (the outputs are "decoded
outputs")it's not decoding BCD to 1in10. I don't think so. I don't know
what is decoded.
I've learned something. Thanks for all contributors. Rich
Aaah, maybe I'm on the right track and fully decoded counters like 4017