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Driving 165 led with a pic or more?!

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gabi68

New Member
Hi to all,

I need to make a circuit to blink, move 165 leds. Take a look at that picture and tell me which is the best approach.
My sign has:
- 60 leds - big ellipse - blink, fading;
- 47 leds - for OPEN word - blink, fading, moving (sort of);
- 59 leds - for 16 TILL LATE word (same as above);
I would like to use a mcu (16 or 18 series) or more but I don't know for sure how circuit look like. I also need 12 V to power up that sign.
Any advice will be appreciated.

Regards
Gabi
 

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Nigel Goodwin

Super Moderator
Most Helpful Member
Using a 13x13 matrix you can drive 169 LED's using 26 I/O pins - obviously you would also require 13 low-side drivers, and 13 high-side drivers.

Fading is probably the most difficult part.
 

DirtyLude

Well-Known Member
It sounds like you don't need to control them all individually, so this isn't hard at all. If all of the LEDs in the 3 groups are doing the same thing at the same time, all you need is 3 i/o's.

If you took away the lines in that diagram, I think I'd have a hard time figuring out what it's supposed to say, though.
 

kpatz

New Member
Do you need independent control of every LED, or can some be combined? For example, if the oval will be made up of "chasing" lights, you could connect every 3rd or 4th LED together so you only need 3-4 I/Os to control them.

How about the words/letters? Are you fading/flashing each word, each letter, each LED within the letter? Combining these into a single circuit where possible will save I/Os as well. Like, if you wanted the entire word "OPEN" to flash on/off/fade as a single unit, those LEDs could be controlled with a single I/O.

If you can determine the flashing/fading patterns you want, the circuit can be vastly simplified over using a 13x13 matrix.

Fading can be done with PWM. No biggie there.
 
My thoughts tend towards the use of hardware on this. Interesting hardware to investigate:

18f1330 - 3 hardware pwm
PCA9635/9685/9698 - NXP line of 16 and 40 bit led drivers (I2C)

Standard GPIO expanders and shift registers also an option, if fading in and out is the only requirement.
 

gabi68

New Member
It sounds like you don't need to control them all individually, so this isn't hard at all. If all of the LEDs in the 3 groups are doing the same thing at the same time, all you need is 3 i/o's.

If you took away the lines in that diagram, I think I'd have a hard time figuring out what it's supposed to say, though.
Yeah now I can see what you mean. First I try to fill up a character with led's but I don't know how to controll all that leds. Do you have a solution for making more readable.

Gabi
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Yeah now I can see what you mean. First I try to fill up a character with led's but I don't know how to controll all that leds. Do you have a solution for making more readable.

Gabi
If you don't want the LED's individually addressable, it makes it MUCH simpler.

But I was imagining it building up the image one LED at a time, like it was been drawn with a pen.
 

gabi68

New Member
Do you need independent control of every LED, or can some be combined? For example, if the oval will be made up of "chasing" lights, you could connect every 3rd or 4th LED together so you only need 3-4 I/Os to control them.

How about the words/letters? Are you fading/flashing each word, each letter, each LED within the letter? Combining these into a single circuit where possible will save I/Os as well. Like, if you wanted the entire word "OPEN" to flash on/off/fade as a single unit, those LEDs could be controlled with a single I/O.

If you can determine the flashing/fading patterns you want, the circuit can be vastly simplified over using a 13x13 matrix.

Fading can be done with PWM. No biggie there.

I was thinking:
1.- chassing for ellipse;
2.- flashing each letter for OPEN - stay lit;
3.- flashing each character 16 till late - stay lit;
4.- repeat 2 and 3.

Maybe to fill up each character will make sign more readable. But again I don't know how circuit look like.
Can you post a shematic design for both - if have time.

Regards
Gabi
 

kpatz

New Member
Here's a version of the image with the LED channels numbered.

You'll see the ellipse has each LED numbered 1-3. All the LEDs labeled 1 would be connected together, all those labeled 2 connected together, and 3 connected together. Thus the ellipse would need 3 I/O pins on the microcontroller. The software would cycle each of the 3 lines one at a time sequentially to get the chasing effect.

Then I numbered each character in the sign. All the LEDs in a given character would be connected together and tied to an I/O pin on the microcontroller.

So to address the ellipse as 3 chasers and the 15 characters individually, you'd need 18 I/O pins, so you'd probably need a 24-pin or larger PIC.

You could use multiplexing, Charlieplexing or wiring the LEDs in inverse parallel to reduce the total number of pins needed, or use helper ICs such as decade counters, serial-in-parallel-out shift registers or decoders.

You'll need transistor circuits to provide enough current to power the LEDs as well.

To make the characters more readable, use more LEDs to fill in the gaps. Since you're addressing by character, you won't need more I/O pins to do this, just more current.

How big is this sign going to be?
 

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Wilksey

Member
Could the "chasing" effect be made from switching on / off alternate LED's?
This could, using the right helper IC's take up 2 I/O pins, by bank switching.

The lettering could again be driven from helper IC's to 1 or 2 I/O pins (depending on if you wish to keep the "OPEN" seperately flashing from "16 Till Late") and to make the "flash" you could use a fast PWM cycle.

165 LED's would need to be sourced and sinked via transistors to a suitable PSU.

You would need to use a "chain" system, where 1 transistor would drive up to a max of say 8 LED's and then continue on this logic, but the transistor inputs could be driven from the same uC O/P input in theory.

Could get messy, unless you are designing a PCB, I made a similar sign, not quite like yours, using IDC Ribbon cable, didn't turn out as neat as originally planned.
 

gabi68

New Member
Could the "chasing" effect be made from switching on / off alternate LED's?
This could, using the right helper IC's take up 2 I/O pins, by bank switching.

The lettering could again be driven from helper IC's to 1 or 2 I/O pins (depending on if you wish to keep the "OPEN" seperately flashing from "16 Till Late") and to make the "flash" you could use a fast PWM cycle.

165 LED's would need to be sourced and sinked via transistors to a suitable PSU.

You would need to use a "chain" system, where 1 transistor would drive up to a max of say 8 LED's and then continue on this logic, but the transistor inputs could be driven from the same uC O/P input in theory.

Could get messy, unless you are designing a PCB, I made a similar sign, not quite like yours, using IDC Ribbon cable, didn't turn out as neat as originally planned.
By mistake do you still have schematics for that sign?

TIA
Gabi
 

gabi68

New Member
Here's a version of the image with the LED channels numbered.

You'll see the ellipse has each LED numbered 1-3. All the LEDs labeled 1 would be connected together, all those labeled 2 connected together, and 3 connected together. Thus the ellipse would need 3 I/O pins on the microcontroller. The software would cycle each of the 3 lines one at a time sequentially to get the chasing effect.

Then I numbered each character in the sign. All the LEDs in a given character would be connected together and tied to an I/O pin on the microcontroller.

So to address the ellipse as 3 chasers and the 15 characters individually, you'd need 18 I/O pins, so you'd probably need a 24-pin or larger PIC.

You could use multiplexing, Charlieplexing or wiring the LEDs in inverse parallel to reduce the total number of pins needed, or use helper ICs such as decade counters, serial-in-parallel-out shift registers or decoders.

You'll need transistor circuits to provide enough current to power the LEDs as well.

To make the characters more readable, use more LEDs to fill in the gaps. Since you're addressing by character, you won't need more I/O pins to do this, just more current.

How big is this sign going to be?
Sign dimensions: 300mmx200mmx??
Do you have schematics or a design or maybe a list of components ?


TIA
Gabi
 

Mr RB

Well-Known Member
Well in the interest of finding a SIMPLER problem to solve, you could do it this way;
Etched Door lit by LEDs - Hacked Gadgets - DIY Tech Blog

You could use 3 sheets of clear acrylic, engrave the signage, then light each sheet from the side. With a diiferent set of LEDs. You can have 3 different colours, 3 different flashrates etc, and it will be TONS easier to make and I think will look much better too.
:)
 
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