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Pure Logic Gates Basketball Scoreboard

Alexander Venus

New Member
Hi im new to this forum and i really need some help. My professor gave us a project to make a scoreboard. The materials to be uses are lm555,74ls90 and decoder ic. Im stuck on the first step because our professor didnt explain clearly. I just know that we need 4 buttons for 1 point 2 points and 3 points. I really need some help and if you can provide a schematic, it will be greatly appreciated. Thank you!
 

dknguyen

Well-Known Member
Most Helpful Member
https://www.electronics-tutorials.ws/counter/bcd-counter-circuit.html

Not sure what the 555 timer is for. Unless your scoreboard is supposed to have a timer.

Your description of needing 4 buttons to do those things doesn't seem quite right since you only need one button to increase the score. Are you sure the three other buttons are supposed to be for something else?

You never said if you're building a full scoreboard or only one digit on the scoreboard. Maybe some of the buttons are to reset the score to zero? Or some of the buttons are for the other team?
 
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dknguyen

Well-Known Member
Most Helpful Member
Thats what im asking our professor :3 what if we exclude the 555? Will the link above satisfy my needs?
That link is should be good enough to get you close to the end. It's defnitely good enough so you have a good idea of what you need to do.

I don't know about the 555 because I don't know what exactly your professor is expecting but I'm assuming he gave it to you for a reason. The 555 seems to be only be needed if you want the scoreboard to be counting something on it's own (like the game time).
 

Alexander Venus

New Member
Ok will try to digest the information in the tutorial. Hopefully i can build a schematic from there. Thanks! Will do a feedback once I encountered a problem or finished it
 

dknguyen

Well-Known Member
Most Helpful Member
Ohhhhhh I see. The 555 timer is so you only have to push the button once for multi-point shots. So for a three-pointer shot you only have to hit the button once instead of three times. Worry about the single one-point per button press version first with reset button. Don't forget to read the device datasheets. Once you get that working you can replace the button with a 555-timer controlled by a button.
 
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dknguyen

Well-Known Member
Most Helpful Member
Yes, the 555 timer is for that. It's not obvious to me though how you would get just a single 555 timer to count X number of times and then stop. How many 555 timers were you given? Just one? Or two?

With two, you would wire each 555 timer in a monostable configuration to transmit a delayed pulse. Each 555 timer sends a signal to the BCD counter to increase the score, but that same signal also triggers the next 555 timer. You also give each 555 timer a button that can also trigger it.

So when you push a button, it immedietely increases the score by 1. But since the 555 timer is also triggered, the 555 timer will send another pulse shortly after to increase the score by 1 again. But this pulse also triggers another 555 timer, so that 555 timer increases the score by 1 again, etc.
 
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Alexander Venus

New Member
Based on the instructions, we can use the materials as much as we needed. Say we need three different 555 for the three buttons then we can do that
 

dknguyen

Well-Known Member
Most Helpful Member
Do the 555 timer last. just focus on a button for +1 point first. Much easier to test.
 

dknguyen

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Most Helpful Member
The LCD part with +1pt button is much easier to test and having it makes the 555 part easier to test. The 555 part alone is less impressive and harder to test when it is alone and obviously you dont want to build everything and test it all at the same time because then it is difficult to debug.

So get the LCD part with the +1pt button working perfectly before doing the 555 timers.
 
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AnalogKid

Well-Known Member
Most Helpful Member
It's not obvious to me though how you would get just a single 555 timer to count X number of times and then stop.
Based on the instructions, we can use the materials as much as we needed. Say we need three different 555 for the three buttons then we can do that
Here is how to do it with three (or four) 555's:

555#1 is the clock (astable) oscillator. This sets how fast the multi-point changes happen. I suggest 2 Hz.

555#2 is a monostable that enables 555#1 for 0.75 seconds. This lets two clock pulses go to the 7490. The instant the clock 555 is triggered, its output goes high; that increments the 7490 by one count. 1/4 second later the 555 output goes low. 1/4 second later (1/2 second total) the clock output goes high again, and the 7490 sees a 2nd clock edge. The last 1/4 second is for margin in case some of the circuits are running a bit short or long.

555#3 is a monostable that enables 555#1 for 1.25 seconds. This lets three clock pulses go to the 7490.

One button goes directly to the 7490 for single-point changes. For consistency, this can be 555#4 acting as a switch debouncer.

The three signals are combined in a NOR gate before going to the 7490 clock input. This is because the 7490 increments its count on the negative-going edge of the clock signal.

ak
 
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absf

Active Member
Here's a reproduction of the description of ak's circuit idea. I purposely left out the single step pulse for you to fill in the blank. Hope this is not Homework or else the Mod would delete the schematic if he sees fit.

Allen
 

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AnalogKid

Well-Known Member
Most Helpful Member
absf - thanks for the effort, but you're not quite there yet. The monostables have to hold the astable 555 in reset to guarantee that it always starts with a complete cycle. In other words, the gating has to come before the astable, not after it.

ak
 
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JimB

Super Moderator
Most Helpful Member
Hope this is not Homework or else the Mod would delete the schematic if he sees fit.
Of course it is homework, the OP said:
My professor gave us a project to make a scoreboard.
As for deleting it, no, I don't think so.
But what this moderator will do, is move the thread to the Homework Help forum.

JimB
 

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