View Full Version : HELP! with small problem please ***ALL FIXED***

11-27-2007, 07:54 AM
I built a 40ch 595 board.

I have written a sequence in 50ms blocks.

I have used the 'simple' and the 595 plugin..... however.....

All the chanells work but not smoothly.

If I flash 2 chanells at 50ms intervals.... every 10th one will skip. They do not 'pulse / flash' evenly.

I can test them....all 40 light up.... no problem.

The preview plugin skips every now and then also.

I am using a 800Mhz P3 computer with 256M RAM.

Is it this?

Do I need pull up resistors? ( Where do these go and what value?)

My power supply is 5.2V ant the plug pack and 4.8 V at the boards.

Any help greatly apreciated :)

11-27-2007, 08:38 AM
Have you set up the parallel port to EPP mode? I think that can cause the problems you are getting if not set to that.


11-27-2007, 09:06 AM
Thanks for the reply Kev.

Yep....EPP mode was set.

11-27-2007, 09:08 AM
What do the De-coupling capacitors do?

I have not put these in.

My 595 is of strip board construction.

Dan Ross
11-27-2007, 09:17 AM
If you built it like the co-op boards use the olsen595 plugin not the simple595 plugin.

11-27-2007, 09:30 AM

I have 5V on the 595 board.

The clk and data pins are putting 3.2V to the board.

Will this cause an odd miss in the lights?

Pull up resistors? I do not understand this.

Is it a pull down resistor between earth and the printer port out' , to stop a floating pin voltage?

11-27-2007, 09:30 AM
Also if your not using the computor for power supply make sure your power supply is filtered,also make sure you used a ground from parrel port to olsen.I didnt think I needed one because i was using the pc power but it would get a random spike.I put the ground on from pin 28 Works fine now.

11-27-2007, 09:32 AM
Yeah... using 595 plug-in.

I'm using a switchmode 5V power supply.

All earths are grounded together ( 5v switch mode and earth pins of the port. )

11-27-2007, 10:36 AM

I've put 2 1004 diodes in to the power line to the 595's..... dropping them to a 4v feed. I have 3.2 v from the port on the scope.

It may be a little better.

Still open to ideas :)

11-27-2007, 05:38 PM
I think I would put in at least a cap or two and see if it helps.

It might be your computer, XP I assume. I'm using a 1GHz with 384MBytes and it can barely handle 160 channels on two Serial and one Parallel port.

11-28-2007, 10:28 AM
The final fix to fully 'smooth' it all out was to upgrade the computer to a 2.4Ghz Intel with 512 RAM.

Is fast and does not miss a beat. :)

Thanks for all help...