# Simple Multiplication of 2, 4, 6, 8.....

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by ikelectro, Mar 30, 2013.

1. ### ikelectroMember

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I want to create a circuit (for my nephew) which will shows the multiplication of 2,4,6 and 8...but I'm able to do only for 2.......not for the other... here is the circuit

And the result is this [video=youtube_share;3_ivwx8NBrc]http://youtu.be/3_ivwx8NBrc[/video]

So How can I do the same also for 4,6,8???????
any suggestion?????

2. ### Diver300Well-Known Member

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You need a significantly more complicated circuit.

As I understand your circuit, it is counting up in 1s, so 1, 2, 3, 4, 5 etc, but blanking the display on the odd numbers so that it is only the even numbers that are shown. If you used the same approach to show the multiples of higher numbers, the display would be off for most of the time.

You are looking for a circuit that produces a fixed number of pulses each time the display is blanked. I suggest a 4017. The clock frequency for that should be much higher than the blanking frequency. The idea is that each time the display turns off, the 4017 is reset. The 4017 counts up until it is stopped. It is stopped when one of its outputs goes high, and that output is connected to a device that turns off the clock input to the 4017. An OR gate should work for that.

As the 4017 has a separate output for each value, you can set the multiplication value with a simple switch connecting any one of the outputs to the device the turns off the clock input.

Or use a microcontroller.

Or film the whole 0 - 99 sequence on the video and edit it to give the values you want.

3. ### ikelectroMember

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I don't want to use the micro.......
and about the 4017 I'll try that... plz stay in touch....

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5. ### ikelectroMember

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the 4017 is working fine in the simulator...... but I'm thinking how to reduce the time for the higher number of value.... If I am able to change the clock frequency more higher for higher number then the time may be the same for all number and of course I have to think about the diffident frequency for blanking input for different numbers.
Can you help in that case?????

6. ### MrAlWell-Known MemberMost Helpful Member

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Hello,

The simplest and most straightforward way is to make a multiplication table logic inside a programmable read only memory (PROM) of some type.
The code to program this is super simple, but you'll need a programmer of some type.
After you get the PROM programmed, you then simply input the two numbers to be multiplied, like 3 and 2 for example, and the output will be 6 of course.
There might be units already programmed out there for sale too.

Second in line is a dual presettable counter with a third standard 'up' counter. One counter is preset to 2 and the other to 3, an the up counter is set to zero. The two preset counters are clocked so that one clocks the other, with the up counting the clocks, and after their combined count gets to zero the up counter contains the multiplication. For the 2x3 example the up counter would contain a 6.

Third is the uC but i see you dont want to use one. That would be cake for one of these devices as you would not need any other chips other than the display driver.

Cute idea BTW, and i would like to see the two multiplicands being shown too, so the display would look like this:

"2 3 6"

or something like that. If you want to get a little more fancy you could add the signs too with small single LEDs in a line or an X shape:

"2 x 3 = 6"

7. ### ikelectroMember

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Hi MrAl,
Fisrt of I want to tell you that Im just 1 year old in electronics so I cant able to learn the micro or how prgm the ROM still now...

So I just want to stay in basic electronics for this project.....

Your second idea is much better for me to think....

Can you consider me to ask you for more elaborate description about the dual presettable counter...

and thank you for your interest in this......

8. ### Diver300Well-Known Member

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You could run the 4017 from a much higher frequency if you want. As it stops after the right number of counts, the upper limit is in the MHz range. If you run the 4040 clock from a higher frequency you can chose which output to give you the blanking at a frequency that looks nice.

9. ### MrAlWell-Known MemberMost Helpful Member

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Hi,

Here is a schematic that illustrates the concept. Make sense?

File size:
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10. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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2, 4 and 8 are just simple shifts (any power of 2 multiply). 6 is the tough one.

11. ### ikelectroMember

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Hi Diver300

Your idea is working nice... I'll post the video and circuit as soon as possible......

12. ### ikelectroMember

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