# Help rebuilding High School project

Discussion in 'General Electronics Discussion' started by Dan91, Oct 21, 2015.

1. ### Dan91

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Oct 21, 2015
Hi all, when i was in high school for my electronics class i build an electronic dice using an astable, counter and NAND gates going into LED's. (This is about 7 years ago now) I have the diagrams and everything still that i made and built it too and i would like to rebuild it to have on my desk kind of thing.
I was hoping someone might be able to help me by looking at the diagrams help me figure out what kind of counter chip ext I need. Thanks!

So far i know i need the following

2) Some cables to connect it all
3) Nand Gates
4) 555 astable
5) LED's
6) a switch
7) a powersupply of some sort (would it be possible to use a battery?)

link to the pictures of my school book

Its been so long since i did it i hardly remember anything i'm also trying to figure out which LED's the numbers at the end refer too i have a feeling its this http://imgur.com/sUYZZSy . thanks.

2. ### Martaine2005

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May 12, 2015

I believe that this circuit is from www.talkingelectronics.com
There are 100s of circuits online to choose from.
The output on pin 3 is definitely different to yours. But the dice is just a random number.
The supply is a pp3 9v battery.

Martin

3. ### Dan91

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Oct 21, 2015
hi martaine thanks for the help. I didnt get the circuit from any site i sat down and had to work it out for myself thats why it most likely doesnt match anything on a site. Will that counter chip fit in my design do you think? as i cannot remember the model of the chip i designed it around. thanks.

4. ### BobK

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1,688
Jan 5, 2010
Did your project light the lights in the same pattern as you see the spots on a die, or did it just have 6 lights to indicate 1 through 6? The circuit Martin posted does the latter. I would prefer the former if I were building it.

If you want to update to the modern world, a microcontroller is the way to go. A single chip, + 1 capacitor + 7 LEDs + 7 resistors would be all the hardware you would need with a micro.

If you don't know what I am talking about, look at the faces of a die. All the numbers can be made by lighting a different set of the LEDs in this pattern:

Code:
```        O             O

O      O      O

O             O
```
Bob

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5. ### Dan91

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Oct 21, 2015
It did light them in the correct order and sequence yes. just like in your code. I dont really want to update to the modern world i know their is most ikely an easier way to do it but i kind of want to just rebuild what i did for my project
At the end where the nand gates go off to the numbers in the diagrams the numbers represent the LEDS in the layout below.

Code:
```O (1)                      O(4)

O(2)          O(7)      O(5)

O(3)                      O(6)```

6. ### Martaine2005

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May 12, 2015
Yes, sorry. That circuit is random with each switch press...
But like I said, there are loads of circuits online.
Keep with DISCRETE. Micro's will own us soon...
I will post a few circuits as I find them that seem like your half of a schem!!

Martin

7. ### AnalogKid

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Jun 10, 2015
The circuit in post #2 can be the starting point for a dice display. That circuit runs at a constant speed until the switch is released, then stops dead. Another variation is a "Wheel of Fortune" circuit that emulates a rotary game wheel in that it starts out fast, then slows down to a halt. Some prefer this kind of visual effect.

Either way, once you have something that spits out 6 states you need to adapt that to 6 light patterns. While this can be done with gates, it is easier to mess with if you use small signal diodes (1N914, 1N4148, etc.). Assign a reference number to each LED, make a table listing which LEDs are to be lit for each of the 6 counter states, and connect each LED to its assigned counter outputs with diodes. For example, the upper right LED would be lit for numbers 4, 5, and 6, so it would have one diode to each of those counter outputs. This is called a diode-OR circuit.

ak

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8. ### BobK

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Jan 5, 2010
That is why we have to own them first.

Bob

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9. ### Martaine2005

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May 12, 2015
I forgot to say..Diode steering.
I wasn't sure if it would work with the random pattern.

Martin

10. ### AnalogKid

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Jun 10, 2015
It's not a random pattern, just a pseudo-random system because the clock is so fast relative to the time it takes for a human to press and release a button. There are 6 4017 outputs and 7 LEDs. Thee only real problem with this approach is the low output current of the 4017. At 20 mA per LED, a 6 needs 120 mA.

ak

11. ### Dan91

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Oct 21, 2015
Ive been researching this tonight i believe that the counter is actually a 7490? This is because i believe my diagram is showing pin 3 and 8 together and pin 2 and 9. On the 7490 it resets to 0 when pin 2 and 3 is high this will happen when the counter gets to 6
pin 9 is QB and pin 8 Is QC then pin 12 is QA which i then allow to flow into my Nand gates. Does this make sense?
Code:
```QD    QC    QB    QA
0    0    0    0
0    0    0    1
0    0    1    0
0    0    1    1
0    1    0    0
0    1    0    1
0    1    1    0```

12. ### Martaine2005

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May 12, 2015
With a 4017, I normally put a transistor at every output used to power more than the original.

13. ### AnalogKid

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718
Jun 10, 2015
Looks good so far. What ever decoding or diode-ORing you do, you have to account for the counter 0000 state Your table has 7 states and a die has 6. As it is now, your circuit might stop on 0000 and make no display.

ak