# How to limit 4029 BCD counter?

Discussion in 'The Projects Forum' started by MrEARTHSHAcKER, Jun 20, 2013.

1. ### MrEARTHSHAcKER Thread Starter New Member

Jun 20, 2013
10
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Hello everyone,

I was wondering how to limit 4029 counter to count only to 9?

Do I need additional logic to detect 9, or I can combine something with the jam inputs?

Thank you!

2. ### absf Senior Member

Dec 29, 2010
1,869
510
One way to do it is inhibit the input when reaching the count of "9".

If you want it to reset to zero on the count of "9", then use the PE input and connect A B C D inputs to Gnd.

Allen

• ###### 4029 count to 9.PNG
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Last edited: Jun 20, 2013
3. ### Dodgydave AAC Fanatic!

Jun 22, 2012
7,601
1,260
You can use the counter in Decade mode by keeping pin 9 low , then when the counter gets to the 9th clk, pin 7 CO will go low so you can use that output to feed pin 2 on the CD4011 chip U2a, and omit the other gate U2b.

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4. ### MrEARTHSHAcKER Thread Starter New Member

Jun 20, 2013
10
2
@absf
I've drawn the signals for your schematics but I don't understand how do we limit the counting using that logic. Shouldn't we have something connected to PE so it enables storing data from jam inputs?

Plus:
Can you guys give me a brief explanation of how these two mods: binary and decade, differ from each other? Binary counts normally 0000,0001,0010,0011 up to 1111 and resets to 0000. And what does the decade one do?

5. ### Wendy Moderator

Mar 24, 2008
21,413
2,946
BCD (Binary Coded Decimal) counts from 0 to 9 in binary. A decoder (such as the 7447 or the 4511) will decode this into a 7 segment display, which we can read easily.

6. ### MrEARTHSHAcKER Thread Starter New Member

Jun 20, 2013
10
2
However, 4029 says "binary/decade". Does binary go up to 16?
Also what is maximum for decade mode?

7. ### absf Senior Member

Dec 29, 2010
1,869
510
That's why I said "one way of doing it"........

If you want it to reset to zero using PE, then it would count 0...9, 0...9 repetitively, is that what you want? Can you show us how you did it?

Allen

Last edited: Jun 20, 2013
8. ### absf Senior Member

Dec 29, 2010
1,869
510
In binary mode, it counts from 0-15, i.e. binary 0000-1111.
In decade mode, it counts from 0-9, i.e. binary 0000-1001.

Allen

9. ### MrEARTHSHAcKER Thread Starter New Member

Jun 20, 2013
10
2
Don't get me wrong Allen. I had no intent to say your solution was wrong.
This is my first practical work ( making a stopwatch counting down ) so I am not good enough to understand some things.

So what I want to do is to make the counter can't go above 9. Because if I want an user to be able to set the timer to some value, and count down from that value, it would be good to disable counting higher that 9 ( since 7-segment display can't show it ).

While looking at your schematic and thinking about Dodgydave's comment, I thought of something. If I connected 6th and 14th pins to AND gate (to detect number 10 ) which would be connected to another AND gate, with another pin connected to a clock signal, and whose output would be connected to PE, I would be able to detect number 10 but directly reset counter to 0000. The only problem... if I did this, it would make 7 segment display show strange stuff for a part of the second since I would be letting number 10 "happen" and there would be some time-gap between counting number 10 and resetting it.

Btw.
Thank you, Allen, for explaining me the thing with decade counter.

10. ### absf Senior Member

Dec 29, 2010
1,869
510
In your original post, you said counting to 9. So that's why I am guessing you wanted to count up. If only you've said you wanted to count from 9........

Do you have a circuit simulator like multisim or proteus or TINA 9.0 or a breadboard to try out your ideas. Actually I've never used the 4029 before but it was in my proteus database so I just go ahead with simulating it. I didn't download the datasheet and that's why I didn't know what the B/D stands for until Dodgydave told me about the decade mode. It suddenly hits me that B/D stands for binary/decade.....

BTW CMOS AND gate is 4081. Your idea might work but you have to try it out. Or else you'll never be sure. I'd try it here with my SIM when I have extra time available...

Allen

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11. ### MrEARTHSHAcKER Thread Starter New Member

Jun 20, 2013
10
2
I have tested it in Multisim, and it works nice.

However, after understanding the meaning of decade counting, I see that it serves my needs perfectly, as it counts only to 9 and it saves me from adding any additional logic for limiting.

Thank you everyone for support, especially Allen

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12. ### tavish New Member

Nov 12, 2014
8
0
I think you just keep pin 9 low, but i'm not positive.