Hi all,

As a part of a project, I have been tasked to create a 2x2 array of lightbulbs (or any other form of signal emitting device) based on a passive matrix, such that I am able to control the output of the bulbs via a PC.

I have gleaned this much so far:
1) I need a USART compatible PIC to 'talk' to my PC for me
2) I need some programme in C language to read the input
3) I need 4 lightbulbs

This is really all I have at the moment, and I will appreciate any form of insight whatsoever regarding how I can go about making such a circuit/program. I have nil knowledge in electrical engineering and circuitry, plus very very basic knowledge of C programming, so please be gentle.

Many many thanks to all!

 

A significant amount of information is missing. Why is there a PIC involved? What do the indicators indicate? What means do you intend to use to maintain the state of the indicators? Are you fixed on lightbulbs? If so, what is the voltage and output requirement?

 

Why do you need any of that? If your PC has a parallel port all is solved. You heaps of I/O on there to control your whole house. If it doesn't have a parallel port then you can buy them very cheaply. Possible cheaper than all those other parts.

 

A significant amount of information is missing. Why is there a PIC involved? What do the indicators indicate? What means do you intend to use to maintain the state of the indicators? Are you fixed on lightbulbs? If so, what is the voltage and output requirement?

The use of a PIC was something my friend told me about; I took it for granted that it would be necessary though I am not completely clear about its function. The setup is supposed to demonstrate that I am able to use a passive matrix to control individual cells of an array by means of an input from a PC, and so I have settled on lightbulbs for sake of visibility. I have not planned what lightbulbs to use as I did not think they would be of significant importance... yet. :s

 

Why do you need any of that? If your PC has a parallel port all is solved. You heaps of I/O on there to control your whole house. If it doesn't have a parallel port then you can buy them very cheaply. Possible cheaper than all those other parts.

This thing about a parallel port is new to me. How do I use it, and how can I connect it to my passive matrix (which I also do not know how to set up)?

 

I would use LEDs instead of light bulbs; they are easier to control with logic-level signals. I'm not quite sure what you mean by a passive matrix; I would start by drawing out the circuit of the 2x2 matrix of LEDs (and current-limiting resistors) and figure out what kind of signals you need to control it.

As for using the parallel port, Microsoft makes that harder with each version of Windows. There are drivers out there that let you directly access the pins from a user-mode program.

/mike

 

I would use LEDs instead of light bulbs; they are easier to control with logic-level signals. I'm not quite sure what you mean by a passive matrix; I would start by drawing out the circuit of the 2x2 matrix of LEDs (and current-limiting resistors) and figure out what kind of signals you need to control it.

Exactly. Light bulbs would be no good.

As for using the parallel port, Microsoft makes that harder with each version of Windows. There are drivers out there that let you directly access the pins from a user-mode program.

/mike

Very very easily fixed..... Give Bill Gates the flick and use Linux. SOOOOOOOOOOO much better

 

Ok, LEDs it is then, thank you! I can't find a good schematic diagram, but basically a passive matrix is one where the wires are connected in a grid pattern. I will need to send a signal up a specific horizontal wire and through to a specific vertical wire, which will be shared by only one LED. I assume resistors will have to be placed such that when the wires are activated, the current flows through the LED?
Sorry I can't make it any clearer. Basically, I think the problem resolves to how I can send signals up the wires I choose from a computer. As to how Linux and parallel ports come into the picture, I am still quite lost.

 

Help wanted, please!

 

This is a well solved problem that you have seen done a million times.

Standard LED scrolling displays connect their bulbs in a matrix to individually light the proper LED at the proper time.

Here is a link to a project that does what you want. (It uses many more than 2x2 LEDS but you can go as big or small as you want)
http://www.jbprojects.net/projects/led/