Single character LED Sign and Clock

In case anyone is interested, I've made some progress on my single character LED sign project. Last week I received some fabricated pcb's from batchpcb (damn they do nice work), and have set out to turn my led sign into a time piece.

More details here:

**broken link removed**

https://projects.dimension-x.net/archives/105

The boards do look nice. It is nice to see that I am not the only thrifty body out there.

Hi Your PCB looks nice to mee too. But I don’t have such a chance to make a board like that. All I do in VERO boards.

I got a super LED these days red colour ones which requires very limit current to operate unlike other ordinary red colour LED’s.

I’m making my own LED matrix board these days on the VERO board. I’m Very tired.
It consists of plenty LED’s as soon as I finish I will show you.

Still the column driver is a problem for me. At the moment I’m doing it with 4017.
It requires additional 10 transistors too.

I’m thinking whether to shift to ULN series or another type of driver IC to drive my columns which has the same RESET & CLOCK pins as 4017.

Hi,
Do you spray on the PCB? Or it is green in color original?

Gayan,
you might want to consider using a ULN2803 in place of discrete transistors, and sacrificing the extra bits on the 4017, so you can match up 8 and 8. Also take a look at the Allegro A6841 - it is a shift register and a high power current sink rolled into one.

i tried using the 4017 in a 24 led matrix, I tied the 4017's clock line to the latch clock for of a 595 register I was using as the row driver. each time I latched new data to the row driver, the 4017 would activate the next column, resetting when it reached column 4. problem is, I didn't bring the reset line to the microcontroller (ran out of pins), so the 4017 would start up in random states, there was also no way to 'skip' a column if I needed to. I switched to using a 74HC139 2 to 4 decoder so I can choose which of the 3 columns are active. danger here is a software malfunction could result in multiple columns being active at the same time, possibly burning out the row driver.

A while back I did some pondering on a modular LED matrix based on high output superflux LEDs (800mA per column), as well as a controller board for it. the article may be of some help to you:

https://projects.dimension-x.net/archives/49

bananas,

the green is called a solder mask - I'm not sure if it is sprayed on or a dip coating. I don't know what color the pcb substrate is - most of the open areas on my design are filled with a ground pour, so you can't really see the substrate at all.

Hi JustDIY thanks for your information.

That’s what I wondering the ULN series.
ULN 2803 is an OCTAL driver is there any DECADE driver in the ULN series (Ten Outputs)?

Because I must avoid using four IC drivers instead of three. I have 30 columns.
I must bare the column drivers from three IC’s with minimum components.

The 4017 works well for me but it requires additional 10 transistors + 10 resistors.

no, you won't find ten, at least not in a power driver IC. Allegro or maybe it was Micrel used to make a 16 bit driver, similar to the 8bit driver.

Gayan Soyza said:

Hi JustDIY thanks for your information.

That’s what I wondering the ULN series.
ULN 2803 is an OCTAL driver is there any DECADE driver in the ULN series (Ten Outputs)?

Because I must avoid using four IC drivers instead of three. I have 30 columns.
I must bare the column drivers from three IC’s with minimum components.

The 4017 works well for me but it requires additional 10 transistors + 10 resistors.

Click to expand...

How are you doing it now with 3 ICs? What 3 ICs? A '4017 and what other 2 ICs? What matrix configuration, 30 by what?

Sorry. Forgot to say;

"JustDIY -- nice job, nice board"... "Very pretty"...

gayan,

hows about just adding two more columns, then you have a 32 bit wide matrix - use two 16 bit drivers and you've saved a chip (from 3 to 2)

I couldn't find the micrel/allegro part, but TI has a 16 bit serial load parallel out register:

https://focus.ti.com/docs/prod/folders/print/sn74ls673.html
https://www.electro-tech-online.com/custompdfs/2007/06/sdls195.pdf

the parts are still listed as "active" but the datasheet is dated 1985, no free samples either

you could go with something like an i2c bus device, maxim makes lots of led driver chips with 16 or more outputs.

How much were the PCBs?

Did you not consider etching your own?

Hero999 said:

How much were the PCBs?

Did you not consider etching your own?

Click to expand...

1) They were about $10 each.

2) I cover that about 1/2 way through my article.

Mike said:

How are you doing it now with 3 ICs? What 3 ICs? A '4017 and what other 2 ICs? What matrix configuration, 30 by what?

Click to expand...

All three IC's are 4017.4017 x 3 = 30 outputs.

Matrix Size 30 x 7 I'm using 7 bits from PORTB.

Thanks justDIY. I referred to the shift registers 8 bit and 16 bit ones but still the additional transistors is a problem.

Gayan Soyza said:

All three IC's are 4017.4017 x 3 = 30 outputs.

Matrix Size 30 x 7 I'm using 7 bits from PORTB.

Click to expand...

A 3 chip solution (no transistors) for a 30 x 7 matrix is certainly a challenge. I hope you don't rule out the Micrel MIC5821 or Allegro A6821 though.