Please help me design a "Multi-digit counter"

Wifilee said:

The counter can count from 0 to 99 and count down from 99 to 0 . Once the reset button is pressed, the counter will reset to 00. If the counter counts from 0 to 9, one of the seven-segment displays should not display any character.

Hint: The control circuit contains 2 decade counters and 2 decoders.


If you all have any circuit diagram , please post it , or also can teach me how should i do. Thank you very much.

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Wifilee said:

Its more helpful for me , but i going to use decade counter ( 74190 ) and decoder ( 74LS47 ) ,can show another example ? Anyway , thank you very much.

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ericgibbs said:

hi,
The 74LS47 and the 74LS247 are the same pin outs.
Are you able to draw in the 74LS90's in place of the 74LS192.??

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Wifilee said:

what for 74LS14? This is fastest way ? No another way ?

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ericgibbs said:

The 74LS14 is to debounce the switch contacts so that you do not get multiple counts on the counter when you press the switches.

Are you able to buy 74LS14.??

I am drawing a new counter showing 74LS90's , I will post it later today.

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Mikebits said:

Is this a homework assignment?

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Wifilee said:

Cause i already bought 74190 IC.......

This is i found in other web ? Any comment for it pic ?

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Wifilee said:

yup , you know how to do it?

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ericgibbs said:

hi,
Look at this 2 decade UP counter, I will let you work out the 'leading zero' blanking of the 74LS147

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Wifilee said:

Thank you very very much , ermmm.....can i ask something ? If i don wan use 74LS14 ,i just want using simple logic gates...like OR, AND, NOT, NOR, NAND gates, can i solve it ? Need any calculation ? How to do?

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hdc090360 said:

As this is a homework assignment, it is not fair to you for us to do all the work. The samples Eric has given you should give you enough hints to complete it. Do you have the datasheets for the 74LS47 and the 74190? You can download them here **broken link removed**

Read them! Knowing the chips is the first step in designing with them.

If you are using switches for your count and reset inputs, then they have to be debounced. The circuit Eric used with a Schmidt trigger is the simplest available. There are many other solutions, but they involve more chips. The 74LS14 is a simple logic gate. It is a NOT gate. The only difference is that it doesn't have an analog region of operation. In other words it is pure logic. Google "debounce schematic" if you MUST use other logic.

Your up/down switch doesn't need debounce. Just make sure you wait at least 20mS after switching it before you press the count button ;-).

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Wifilee said:

Ok , i done the 2 digit counter circuit already , can you teach me or give me some information how to add reset button in circuit ? Need any calculation ? you no need show me ,just teach me , i will do myself . Thank you very much .

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ericgibbs said:

hi,
I have already shown you how to connect a RESET button, its called CLEAR on the drawing.

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hdc090360 said:

Have a look at this website.

Electronics Tips: Contact Bounce and De-Bouncing

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