Counter Down 129-0 with Seven Segment need some help

Discussion in 'The Projects Forum' started by shiroi, Oct 15, 2012.

1. shiroi Thread Starter New Member

Oct 12, 2012
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Hi everyone, pleased to meet you all

im new here, i given a task by my lecturer to make Counter down from 129 to 0 but well i have really some problem but first actually i already have a counter down, but it's counter from 15-0, idk how to get it so it can count from 9-0 pls help me, mybe some advice how to get that? or mybe i need to change my IC? this is my picture

2. donpetru Active Member

Nov 14, 2008
186
25
You need to change tactics to achieve circuit. For example, try to build a counter with 2 pieces CD4026 (see image below):

3. MrChips Moderator

Oct 2, 2009
12,635
3,454
Replace the 74193 with 74192. Read the datasheet on how to cascade 74192 counters.

4. shiroi Thread Starter New Member

Oct 12, 2012
5
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thank you mr chips and don

now i have 3, 7 segment, but i cant set the number i want. it's only counter from 9-0
wonder what happen strangely not count from 15 again, my question is how to set the number so i can like i want? thank you

5. MrChips Moderator

Oct 2, 2009
12,635
3,454
Did you read the data sheet?

Connect TCU of U1 to UP of U2.
Connect TCD of U1 to DN of U2.

Connect TCU of U2 to UP of U21.
Connect TCD of U2 to DN of U21.

6. shiroi Thread Starter New Member

Oct 12, 2012
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ahh my mistake, now it's 999 trying to figure it out now thankyou

7. MrCarlos Active Member

Jan 2, 2010
400
134
Hello shiroi

But you mentioned in your original message that the counter is down from 129 to 0.
What you did not mention is what to do when that counter reaches zero.
Stop ??
Continue cyclically counting from 129-0 ??

If this counter is going to stop when it reaches zero should be detected when it reaches zero and at that moment you stop pulses reach the first counter, the one that count units.

But if the counter must be cyclically from 129 to 0 it is necessary to detect when the counter reaches 999 and then instantly reprogram it to 129.

regards

8. shiroi Thread Starter New Member

Oct 12, 2012
5
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my lecturer never said if it should Continue cyclically or not, mybe i will ask someone

now mine can count from 129, but it seems i need to load it manually (Change Low to high) so it will counter normally and when it's end to counter 129-0 it will start again from 999

1. how to change the LOAD automatically so i dont need to do it manually?
2. how to "counter again"/Stop it when it's finish to count from 129-0 ?

Thank you

9. elec_mech Senior Member

Nov 12, 2008
1,513
193
One way to do this is to trigger the load pin on each 74192 when the count goes from 000 to 999. Since your current design will never be above 129, you can look at the output of the MSB or the middle 74192 since neither should ever be 9.

From here, you need to figure out how to read a 9 and send a signal to the load pins.

One way is to use logic gates with diodes or transistors as shown here: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diodgate.html. You can also simply use IC logic gates if your professor allows it.

I don't want to just give you the answer, so think it over, try something out, and ask questions once you've tried a solution.

10. takao21203 Distinguished Member

Apr 28, 2012
3,578
463
Well I give the answer (one possible solution): Add comperators for 999, AND them together and route that to the tristate input of transceivers which in turn preset the counter. It will make the circuit quite large and will keep you busy for a while.

If that's too much effort, don't use TTL gates at all. I have not looked into the details if the counter is presetable.

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11. MrCarlos Active Member

Jan 2, 2010
400
134
Hello shiroi

According to the rules should be no entry without a defined level either high or low.

The 7-segment display's require limiting resistors, one per segment.

The attachment circuit could meet the requirements to develop yours.
analyze it and give me your opinions.

regards

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12. MrChips Moderator

Oct 2, 2009
12,635
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Good point. He is doing a simulation so he cannot see the smoke.
It will be a different story when he wire this for real.

13. MrChips Moderator

Oct 2, 2009
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Take a look at TCD of U21 and see when that changes state.

14. ScottWang Moderator

Aug 23, 2012
4,930
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If you wish to use the number count down from 129 to 0, then you can use CD4510 Decimal UP/Down Counter with preload.

74LS192,74LS193 are the binary UP/DN counters, but you need a decimal UP/DN counter, it can be count up to 9, and count down to 0 through preload function.

CD4026 is a good IC, but you can't use it at here, because you need a preload function, CD4026 didn't have the function.

1. You need to use CD4510 with preload 129 function.
2. You need to add a checking circuit to check when the 129 is coming, then reload the 129 to the output of the counter.
You need the AND gate function to do the jobs, you can use logic IC 74LS08 AND gate.

The AND gate that you can use as 74LS08,74HC08,74LS11,74HC11.

CD4510.
http://www.datasheetcatalog.org/datasheets/150/109581_DS.pdf

74LS08
http://www.datasheetcatalog.org/datasheets/70/375337_DS.pdf

Parts search engine:
http://www.datasheetcatalog.org

15. elec_mech Senior Member

Nov 12, 2008
1,513
193
74LS192 is a BCD counter (what you are referring to as a decimal counter) while 74LS193 is a binary counter. Both of these have a preload function.

I think you are referring to post #2 which was a suggested solution from another member, not the OP.

It should be clarified CMOS and TTL don't usually play well together, so if the OP ops to use the 4510, he'll need to replace his other ICs with CMOS equivalents and change his power supply from 5VDC to 6-15VDC.

Ditto - excellent catch Mr. Carlos.

Ah, read MrChips's excellent observation above very carefully. This will solve your reset issue without the need for extra parts and could be used to help you stop your circuit.

16. ScottWang Moderator

Aug 23, 2012
4,930
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Thanks elec_mec, it's my fault.

yes.

If using the same IC series is better and easier, that's true, but when you know how to connected CMOS and TTL together, then you will have the different feeling, I changed to use CMOS from TTL was over 20 years, using TTL just for some cases.

I think when CMOS connecting to TTL is easier, but when TTL connecting to CMOS, the TTL should be add pull up resistor, if he use CD4510 that he doesn't need to change the Power, because CD4510 also can working at 5V very well, I'm not sure why you said that it should be change and increase the power.

17. elec_mech Senior Member

Nov 12, 2008
1,513
193
Whoops, you are right. I need to double-check the datasheets before I type. For some reason I have 6-15VDC in my head - I think I'm mixing up CMOS with ULN2003 vs ULN2004 chips (been working with those lately).

I shall have to try mixing CMOS and TTL together as you suggest. Lately I've just stuck with CMOS so I wouldn't be forced into using a 5VDC regulator, but I have a lot of TTL chips on hand I'd hate to not use. Thank you for the advice.

18. ScottWang Moderator

Aug 23, 2012
4,930
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I don't like to use the TTL, because they are eating too much current, I also had some TTL series in my hand, but almost for the labs and testing.

I studied EE from the old tube age, so like as Tube, CRT, TTL that's what we have to learn in the school, when I get into a industrial company to deisgn the counter, timer, controller etc, since then I have to use CMOS for my work, and also have to use much more caps and resistors to avoid the noise affecting the counters, timers, because they were working in the factory, they have much much more machines could damage the work of counters, in that kind of the bad environment, RC filters is very important.

You can look something good for the logic IC interfacing.

74HCxx and 74HCT and TTL Series Related Application Details. 74HCxx and 74HCT and TTL Series Related Application Details.

The voltage of the Logic's level.
The CMOS families [74ACxx, 74HCxx, 74AHCxx, and 74Cxx] have different input and output switching levels than the TTL logic devices [74Fxx, 74Sxx, 74ASxx, 74LSxx, and 74ALSxxx].
http://www.interfacebus.com/voltage_threshold.html

Last edited: Oct 17, 2012
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19. shiroi Thread Starter New Member

Oct 12, 2012
5
0
thank you takao and everyone else, my task now is finished, not perfect but i think it's good enough to get submitted. im using TTL and Comparator as takao suggested. i have a question

is it possible to get my LSB counter from 9? mine always counter from 0,9,8. i'm using IC 7447 and 74192 and a comparator

20. elec_mech Senior Member

Nov 12, 2008
1,513
193
I'm not sure what you are asking. Could you elaborate and explain what it is you want the circuit to do?

Posting your current schematic would help.