5x7 LED matrix fixed display

[Englishman in Ankara]

Maybe I'm trying something too simple, but I couldn't find what I need
on the 'net...

I want to display a fixed message on a 5x7 matrix LED panel. Actually a
few (6 or 7) side by side.

The only circuits I can find are for SCROLLING displays.

Is there a simple way of driving a multiplexed LED display? maybe using
simple logic not PIC or microprocessors.

Any ideas would be appreciated...

 

[Pooh Bear]

Maybe I'm trying something too simple, but I couldn't find what I need
on the 'net...

I want to display a fixed message on a 5x7 matrix LED panel. Actually a
few (6 or 7) side by side.

The only circuits I can find are for SCROLLING displays.

Is there a simple way of driving a multiplexed LED display? maybe using
simple logic not PIC or microprocessors.

Any ideas would be appreciated...

You'll need a processor. I'd use an 8051 family part most likely.

Oh, unless you really mean a *fixed* message in which case just connect the
leds that make up the characters to some power and leave the other ones
unconnected.

Graham

 

[mmm]

Maybe I'm trying something too simple, but I couldn't find what I need
on the 'net...

I want to display a fixed message on a 5x7 matrix LED panel. Actually a
few (6 or 7) side by side.

The only circuits I can find are for SCROLLING displays.

Is there a simple way of driving a multiplexed LED display? maybe using
simple logic not PIC or microprocessors.

Any ideas would be appreciated...

maybe a bunch of shift register connect in a circular fashion can do the
job, break the connection to load the new datas, plus some counters and
decoders plus some mixed gates to connect all.

but the question is :

using discrete logic you need lot of chips, using a micro you put inside
the micro the 'data memory' and the all logic to do the refresh and
you need only the led drivers outside the micro.

I tought that at slow speed micro almost always beat discrete logic, my
pcb maker charge lot of money and a single micro is soooo small !

 

[Frank Bemelman]

You'll need a processor. I'd use an 8051 family part most likely.

Oh, unless you really mean a *fixed* message in which case just connect the
leds that make up the characters to some power and leave the other ones
unconnected.

Those displays are a matrix, 5+7 -> 13 pins. You need a character
rom, and a lot more rubbish.

It's like you say, a job for a microcontroller. Or single leds,
or just a piece of cardboard with some holes in it

 

[Spehro Pefhany]

maybe a bunch of shift register connect in a circular fashion can do the
job, break the connection to load the new datas, plus some counters and
decoders plus some mixed gates to connect all.

but the question is :

using discrete logic you need lot of chips, using a micro you put inside
the micro the 'data memory' and the all logic to do the refresh and
you need only the led drivers outside the micro.

I tought that at slow speed micro almost always beat discrete logic, my
pcb maker charge lot of money and a single micro is soooo small !

Here's an example circuit and firmware using an older PIC type
microcontroller. Lewin used discrete LEDs but it would work fine with
an LED array.

http://www.zws.com/products/picxie2/index.html

 

[petrus bitbyter]

Maybe I'm trying something too simple, but I couldn't find what I need
on the 'net...

I want to display a fixed message on a 5x7 matrix LED panel. Actually a
few (6 or 7) side by side.

The only circuits I can find are for SCROLLING displays.

Is there a simple way of driving a multiplexed LED display? maybe using
simple logic not PIC or microprocessors.

Any ideas would be appreciated...

If I understand you well, you need to drive six or seven 5x7 displays. So
you have to control 72 or 84 lines. Even if you combine the long side, it
will be 37 or 42. Now you have several possibilities:
- You can consider it a challange to build it in logic. Not my choice and I
guess you should not have posted here if it was yours.
- You can use a pretty big micro or a smaller one with additional logic.
Requires a kind of development system and some programming skills.
- You can use a PLD. Same requirements as for a micro.
Neither of the possibilities seems attractive as you need either big,
expensive components or a lot of cheaper ones. So I advise to chop the
display in smaller parts and use one micro for two or three matrices. This
way you need only two or three relative cheap micros that all run the same
program although with a different display list. You still need a kind of
development system but it can be build cheap. Both examples, designs and
software are available free on the net.

petrus bitbyter

 

[Pooh Bear]

Those displays are a matrix, 5+7 -> 13 pins. You need a character
rom, and a lot more rubbish.

I was thinking he could make a discrete matrix maybe.

It's like you say, a job for a microcontroller. Or single leds,
or just a piece of cardboard with some holes in it

I tend to the latter solution too !

Graham

 

[Luhan Monat]

Englishman in Ankara wrote:

Is there a simple way of driving a multiplexed LED display? maybe using
simple logic not PIC or microprocessors.

No.

 

[Donald]

Englishman in Ankara wrote:




No.

Of course it can be done with simple logic.

Lot and LOTS of simple logic chips !!!


;-0

 

[Spehro Pefhany]

Of course it can be done with simple logic.

Lot and LOTS of simple logic chips !!!


;-0

Lots? I think only a few.

1 - 1/6 hex ST inverter plus two passives (clock oscillator)

1 - HC4017 connected as divide by 7

7 high side drivers driven by 0..6 of 4017 (discrete or hex inverter
1/6 of ST inverter plus p-channel MOSFETs)

7 low drivers driven by 0..6 of 4017 (discrete- n-channel MOSFETs)

1 resistor per column (5 x number of characters)

1 1N4148 diode per illuminated LED


That adds up to 3 ICs, 14 MOSFETs, 1 + 5*n resistors, and from 1 to
35*n 1N4148s, plus a capacitor or two.



Best regards,
Spehro Pefhany

 

[petrus bitbyter]

Of course it can be done with simple logic.

Lot and LOTS of simple logic chips !!!


;-0

There is an easy way. Take a shiftregister that adresses one column per
display at a time. Tie the rows to Vcc via a resistor. A clock will drive
the shiftregister and all leds light up. But as you have a fixed text you
can blackout all unwanted LEDs by a felt-tip or a sticker. It's not my
prefered solution but it's the most simple one I can imagine. Per display
you need a shiftregister and a gate to controll it. As the logic may not be
able to drive the LEDs, you may need some buffers. You can use one clock to
drive all shiftregisters. Even then, chipcount and boardspace are high
compared to one micro/two displays. (I'm sure one micro/three displays is
also possible.)

petrus bitbyter

 

[John Fields]

Of course it can be done with simple logic.

Lot and LOTS of simple logic chips !!!

 

[Luhan Monat]

There is an easy way. Take a shiftregister that adresses one column per
display at a time. Tie the rows to Vcc via a resistor. A clock will drive
the shiftregister and all leds light up. But as you have a fixed text you
can blackout all unwanted LEDs by a felt-tip or a sticker. It's not my
prefered solution but it's the most simple one I can imagine. Per display
you need a shiftregister and a gate to controll it. As the logic may not be
able to drive the LEDs, you may need some buffers. You can use one clock to
drive all shiftregisters. Even then, chipcount and boardspace are high
compared to one micro/two displays. (I'm sure one micro/three displays is
also possible.)

petrus bitbyter

Ok, you missed it then. Tie each anode line to vcc via an appropriate
resistor. Tie all cathodes to ground. Block out unwanted LEDs with
felt-tip marker.

Viola!

 

[Luhan Monat]

Ok, you missed it then. Tie each anode line to vcc via an appropriate
resistor. Tie all cathodes to ground. Block out unwanted LEDs with
felt-tip marker.

Viola!

Ooops, Voila!

 

[petrus bitbyter]

Ooops, Voila!

--
Luhan Monat: luhanis(at)yahoo(dot)com
http://members.cox.net/berniekm
"Any sufficiently advanced magick is
indistinguishable from technology."

Yeah, you're right. You don't need any shiftregisters at all. Suppose you
mean you posted it before? So I missed it, which is pretty common. Sometimes
even miss my own postings. ISPs newsservers tend to be lousy. Can of course
look for special newsprovider but hate to pay something twice. Voilà.

petrus bitbyter

 

[Pooh Bear]

Ok, you missed it then. Tie each anode line to vcc via an appropriate
resistor. Tie all cathodes to ground. Block out unwanted LEDs with
felt-tip marker.

Viola!

Violins !

And sure that'll work fine. ;-)

Graham

 

[Luhan Monat]

Yeah, you're right. You don't need any shiftregisters at all. Suppose you
mean you posted it before? So I missed it, which is pretty common. Sometimes
even miss my own postings. ISPs newsservers tend to be lousy. Can of course
look for special newsprovider but hate to pay something twice. Voilà.

petrus bitbyter

By 'missed it' I only meant that you were damn close. I would not have
seen it myself were it not for your posting.

As a 'technical improvement' on the solution, the OP could set up a 2
amp power supply an 'blow' selected LEDs like fuses. Then, the ones
left would form the characters without wasting current on unwanted LEDs.

 

[[email protected]]

Maybe I'm trying something too simple, but I couldn't find what I need
on the 'net...

I want to display a fixed message on a 5x7 matrix LED panel. Actually a
few (6 or 7) side by side.

The only circuits I can find are for SCROLLING displays.

Is there a simple way of driving a multiplexed LED display? maybe using
simple logic not PIC or microprocessors.

Any ideas would be appreciated...

maxim 7219 can drive 5x7 matrix displays

 

[Donald]

Simple, Cheap, easy to build. Pick two.

 

[Spehro Pefhany]

maxim 7219 can drive 5x7 matrix displays

I think generating the SPI signal for the 7219 might be even more
unpleasant than generating the drive signals directly.


Best regards,
Spehro Pefhany