Please help with some basic info on controlling an LED matri

[Justin98TransAm]

Hey guys, me again. Thanks for the help on my previous questions, now I"ve got another.

I want to controll a 7x23 Segment LED matrix. I need to be able to have the matrix perform 1 of at least 3 "Programs" depending on a triggered voltage. like, if input 1 sees 12 volts to do one thing, if input 2 sees 12 volts do another thing and so on... My questions are, What is the easiest controller to use, how do you program the controller, how do you "switch" between programs, can a controller control brightness of the led? That's all I can think of at the moment, any help would be greatly appriciated.

Thanks,
Justin

 

[Someone Electro]

You wod have to use an high curent multiplexer.

 

[Justin98TransAm]

You wod have to use an high curent multiplexer.

which one shold I use? I'd like to be able to have 3 different programs run triggered by inpuit voltage on 3 different inputs, but I'd also like to be able to use the array as a scrolling sign. Is this possible?

 

[bonxer]

When asked what is the easiest controller to use, the answer of course is the one that is used by the most people you know so you can get help. The preferred microcontroller around here is the PIC from Microchip. It will take a while to learn, but it can most likely handle what you want to do. There are diagrams on how to make your own programmer, and places to buy them pre-made. Then you are going to need to obtain a PIC. The 16F877 is a standard one to use. You could use a 16F871 which is the same thing but less memory and a little cheaper. These have 33 I/O pins. You could have your 23 column controls, 7 row controls, and 3 inputs. It would fit the physical pin requirements, but there's no room to grow. You could have no additional inputs or outputs without some modifications. Anyway, once you get a programmer, the first logical place to start is to get a tutorial that will show you how to blink a single LED. Then from there, blink 8 LEDs at the same time, which will be a really really simple modification. From there, blink 24 LEDs. Then change it so it only does 23 LEDs. Then once you've got that idea down, put different patterns on each of the 23. Once you're comfortable with that, you can strobe them. One control signal will activate row 1, then you load your 23 LED patterns. Turn off row 1, activate row 2, then load the 23 LEDs with the second line of your image, 3rd, 4th, etc. The amount of time that they are on and off will control their brightness. If they are on for a longer period than they are off, they will be brighter. As for the inputs, it would just be a simple IF / THEN / GOTO to determine which patterns get sent to the 23 column outputs.

This will take a long time for a beginner to do, and most likely you will have to code just about everything from scratch. There will be lots of learning, but we're here to help.

 

[Justin98TransAm]

sweet Thanks for the help. how much are we talking for a pre made programmer, and chip? i'd rather have the one with more memory. Is there a way to load a "font" so that if I wanted to scroll text i wouldn't have to program each LED for the text?

 

[Someone Electro]

An PIC can only deliver 25mA per pin i od use an multiplexer to light more LEDs at once

 

[pittuck]

sweet Thanks for the help. how much are we talking for a pre made programmer, and chip? i'd rather have the one with more memory. Is there a way to load a "font" so that if I wanted to scroll text i wouldn't have to program each LED for the text?

Pre made programmer = £15 to £150

Home made, no idea.

As for fonts, EEk. ur best bet would be some i2c EEPROM to store the info (can store the whole extended ASCII set on some EEPROMS). Chose ur font on windows and take a screengrab of all the letters and work out the point positions yourself.

Some other people may have other ideas...

 

[Someone Electro]

heres the whole thing alredy build realy cheap. (has LEDs whith multiplexers to drive them)

**broken link removed**

All you need is an PIC to contole it.

 

[Justin98TransAm]

heres the whole thing alredy build realy cheap. (has LEDs whith multiplexers to drive them)

**broken link removed**

All you need is an PIC to contole it.

Cool, but I've alredy got the LEDs mounted in the form that I need them, I just have to hook up all the transistors to form the matrix (fun stuff) then as this thread states, I gotta learn how to control the whole thing

 

[bonxer]

how much are we talking for a pre made programmer, and chip?

The 877 chip itself will be around $7 to $10, depending on where you get it. Programmers can range from $12 for an ultra cheap "maybe it will work" model up to hundreds for an official thing from Microchip, Inc.

Is there a way to load a "font" so that if I wanted to scroll text i wouldn't have to program each LED for the text?

You will have to create and program your font once. Hardcoding entire frames, where you have to go through and manually draw a letter in a different position each time, would be extremely tedious. Instead, say for example that you just drew the letter A and stored that in memory. You could put this in an EEPROM as pittuck suggested, or if you've got lots of programming memory left (for this project, you will), you could just store your entire font library in the program code itself. To use it, you would just have an X variable and a Y variable. You just put in the location you want to display, load the address for your 'A' character, and call your 'Draw Letter' function.

 

[Justin98TransAm]

sweet, that's exactly what i'm looking for. Okay, so what programmer do you guys suggest? Do you have a favorite?

 

[Nigel Goodwin]

sweet, that's exactly what i'm looking for. Okay, so what programmer do you guys suggest? Do you have a favorite?

The P16PRO40, running either WinPicProg or ICProg (both free programs).

 

[pittuck]

my 'new' favourite is the ICD2 + BoostC C complier

lol, sparkfun order arrived hehe

 

[bonxer]

I use the Epic Plus programmer from microEngineering Labs, **broken link removed**. It costs a hundred bucks, which the price sux, but its what my group used in college, so I got one too. It always works. It programs a chip very fast. I've never had any problems with it. Plus they are pretty prompt at updating their software to program new PICs as they come out. This one is parallel port. They also make a serial port version.

**broken link removed** has a USB programmer for $60. I've never used it, but it looks decent.

https://olimex.com/dev/index.html has a bunch of different programmers. My only exposure to them is their PIC-PG2 programmer (which is teh sux) based on the JDM. My friend likes it because it's cheap. I hate it because it's slow. Painfully slow. Plus there are lots of reports that it doesnt work right on all computers. Their other programmers that have an external power jack look alright. I dunno about their speed though. Just stay away from anything that says it's JDM based.

Other people have links in their signatures that lead to places where you can get reliable PIC programmers and in-circuit debuggers too. Investigate a little, and you should be able to find a pre-made programmer you can buy that fits your budget and has the features you need.

 

[Nigel Goodwin]

It costs a hundred bucks, which the price sux, but its what my group used in college, so I got one too. It always works. It programs a chip very fast.

If speed is an issue?, my software WinPicProg is probably the fastest programmer available?, (it was also the first Windows based PIC programmer - many versions ago!). The slowest is probably the PicStart+ from MicroChip, they are pitifully slow!.

 

[pittuck]

this is what i have:

**broken link removed**

sorry, nigel, this is faster than urs although it comes at a price and the IDE is crap!

 

[bonxer]

If speed is an issue?, my software WinPicProg is probably the fastest programmer available?, (it was also the first Windows based PIC programmer - many versions ago!). The slowest is probably the PicStart+ from MicroChip, they are pitifully slow!.

I wouldn't think speed would be an issue either until I used that crappy PIC-PG2 programmer which took 4 minutes to program an 18F452!

 

[pittuck]

lol, try IC-PROG w/ 18F452

talking 50seconds... It programs all the memory where winpicprog only programs the 'sections' which need programming after doing a erasing.

I am not sure but by erasing the EEPROM goes right? And this way ICPROG can keep settings in EEPROM, BUT not run the risk of programs overflowing into old program space?

Of course, win pic prog if i remember correctly only verifies the programmed spaces? whereas IC-PROG then has to check all the program memory. So verify will be long also .

 

[Justin98TransAm]

cool. I have no problem spending 100 bucks for a good programmer. So i guess my main concern is that it's good, and that a lot of people here are familiar with it, becasue I'm going to need help

 

[Nigel Goodwin]

this is what i have:

**broken link removed**

sorry, nigel, this is faster than urs although it comes at a price and the IDE is crap!

Well the ICD2 ISN'T really a programmer :lol: , it's an 'In Circuit Debugger'.

I've never used one, but as it's driven by MPLAB I would presume it has the speed limitations of MPLAB?.

If it's programming the target device via a bootloader, bootloaders are fast - otherwise I don't see how it can be faster than WinPicProg?.