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Multiplexing and DeMultiplexing Answered

Hello, I first was wondering if anybody knew anything about Multiplexing? if so then you will understand my question here :)

So basically I have this crude diagram that will explain what i'm talking about: http://i.imgur.com/T0V5zV5.png?1

now my problem is I now have 9 control signal wires, is there any way around this?

Again if you know about multiplexing then you should hopefully understand my question, based on the diagram. 

thanks for the help :)


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mrn (author)2013-04-09

I apologize for the all the confusion.

Basically I need a grid of 64x64 64 rows and 64 columns, controlled by either 8 595's or 2 MAX7221's

the points on the grid are made up of some type of tiny valve, that regulates fluid.
So when the valve is activated, it is opened for a tiny fraction of a second, letting in a tiny amount of fluid, down a small tube.

as steveastrouk stated there is trade offs for using the 595's verses the MAX7221's
Pricing is a consideration also.

My very large problem at the moment however is a suitable valve, that is 1/8 of a inch
that can block fluid, about the consistency of water possibly a little thicker.

My first thought was a simple magnet and wire, where there would be a very tiny U shaped piece of copper wire, and above that a tiny magnet, ans so when the wire is activated(applied voltage) it gets attracted to the magnet above it, thus opening a small crevice for fluid to flow down the tube.

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steveastrouk (author)mrn2013-04-10

Copper wire isn't magnetic, so your coil won't attract it !
You will be shocked how much force it takes to pinch off the tube.

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mrn (author)steveastrouk2013-04-10

But you apply a voltage to the wire making a tiny electromagnet. right?
I know it isn't a coil however, from a simple test I did, it still works well.


I wont be pinching the tube, instead think of a flapper, sitting on the top of the tube, and when it opens, fluid flows into the tube.

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steveastrouk (author)mrn2013-04-10

Try it, see how much force the tubes take to close. A coil needs a core to work efficiently

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caitlinsdad (author)mrn2013-04-09

So I take it this was all about building the ultimate bartending bot without your parents finding out. That's 4096 solenoid valves you're looking at controlling. $$$ or whatever your currency is.

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mrn (author)caitlinsdad2013-04-09

Actually I wont be using solenoids, as you mentioned the high price. But instead what I mentioned above the U shaped wire and magnet.

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caitlinsdad (author)mrn2013-04-09

How did you intend to unstick the wire from the magnet to drop the wire so it closes your opening again? You have to have a good seal to block the liquid.

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mrn (author)caitlinsdad2013-04-10

when the voltage is let go the wire will drop back down, ill be using a material that is super light and flimsy so that the weight of the wire will push it back down.

However as you mentioned sealing this from the liquid would be hard.

there is no way that this will block fluid, I don't think anyways.

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caitlinsdad (author)mrn2013-04-10

Which brings us back to your original question. Why do you have 9 control wires? Each with a different number for each stage of your muxing demuxing? What are they for and what are you using to provide the control signals? It comes down to what you are doing. How did it change from LEDs to control valves? If it is an idea you want to discuss, fine, but it is hard to help if you can't specify what you are trying to do which shows you don't know what you want to do.

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mrn (author)steveastrouk2013-04-07

Isn't this specific to controlling a LCD segment display?

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mrn (author)steveastrouk2013-04-07

But I will need several of these, each with there own control signal though, wont I?

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steveastrouk (author)mrn2013-04-08

Your diagram shows 64 LEDs, the Max 7221 will drive 64 leds. If you want more, look at the datasheet it shows exactly what to do.

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mrn (author)steveastrouk2013-04-08

considering I will need several max's they are pretty expensive, what if I chained together several 74HC595's?

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steveastrouk (author)mrn2013-04-09

Much more work. Trade off effort against results. How many LEDs do you NEED ? There are other chips like the 7221. Look for them.

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caitlinsdad (author)2013-04-06

It would help to know what chips you are using? Something on a PC driving the display?

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mrn (author)caitlinsdad2013-04-07

I'll be using a parallel port, sorry for some reason the image I added isn't showing up.

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caitlinsdad (author)mrn2013-04-07

So you are pushing a byte out the parallel port. What is controlling the chips?

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mrn (author)caitlinsdad2013-04-08

what do you mean? do you mean power?

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caitlinsdad (author)mrn2013-04-08

I'm only trying to pin down what you are asking. Have you looked through all the other instructables to see how to drive an 8x8 LED matrix or even start with a smaller sized one? You need to know what other parts are necessary in your design like are you using a microprocessor or just trying to take a serial output to get a display pattern on your LED. What have you got and what are you trying to do?

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mrn (author)caitlinsdad2013-04-08

ill be using a parallel port and some either multiplexers or a shift registers

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caitlinsdad (author)mrn2013-04-08

the problem is we can't help you if we don't have a clue of what you are doing so it is hard to help you.. For example, in the most general terms, do you want to have a scrolling LED display driven by a C++ program or want to display a tweet through the parallel port or just want to make a nice visual display? Good luck.

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