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rjanuary
06-06-2007, 07:08 PM
I just built an eight channel 595 board with built in SSR's. It runs flawlessly on a PC though has problems running off my laptop's parallel port. I heard there are differences in line voltages between the two. What's the easiest way to modify the 595 to work with a laptop?

Thanks in advance!

Richard

A Marchini
06-06-2007, 07:20 PM
I just built an eight channel 595 board with built in SSR's. It runs flawlessly on a PC though has problems running off my laptop's parallel port. I heard there are differences in line voltages between the two. What's the easiest way to modify the 595 to work with a laptop?

Thanks in advance!

Richard

Well there are many schools of thought on that.
My personal preference is to get a 74HC14 as a go between for the signals. It can buffer up to six lines and you only need 3 (unless you are doing a full parallel port in which case 2 chips will be needed). It would be connected to the 5V supply that your 595 is connected to.

Other ideas are adding a little voltage drop to your circuit input and reduce the operating voltage down from 5 volts.
I think all goes pretty well at 4.5 volts.

I am big on running the chips at 5 volts.

Tony

Macrosill
06-06-2007, 07:49 PM
Might also be the posrt setting in the bios. I ran into that problem when I first started. Try the different port settings before going crazy with other things. I think mine run in the EPP mode.

rjanuary
06-06-2007, 08:23 PM
Might also be the posrt setting in the bios. I ran into that problem when I first started. Try the different port settings before going crazy with other things. I think mine run in the EPP mode.


Appears that my laptop's Bios doesn't have an option to change the port settings. I have a HP Pavilion ze4400.

Richard

FireGod
06-06-2007, 10:15 PM
Build an adjustable voltage regulator. You can get all the parts from Radio Shack. The diagram of how to build it is on the back of the regulator package (LM317). The adjustable pot can be a 10k 10 turn pot that they will have at the store.

By dropping the voltage just a little it usually works fine.

wjohn
06-06-2007, 10:35 PM
Hi,

You have come across a common problem. Most of the the time it seems to be that the voltage coming out of the LPT port is not high enough to be seen as a Logic One by the 595/GRINCH ICs.

What I did, and it worked, was to change the voltage I run the board at. While the following section talks about the GRINCH controller, the premise is the same and can be applied to the 595. I used a variable power supply to find what voltage the contoller would operate consistantly from. FG's suggestion is correct, I used a LM317 as the regulator in my power supply. Using a variable resistor to start with, find the correct operating voltage, and then replace the variable resisitor with a fixed resistor of the correct value.

Some people have had issues with low voltage on their parallel port of their PC with the 595 in the past and I had a problem with my first GRINCH. My Dell PC only provides 3.32Volts on the LPT: port. This was insufficient to trigger the MBI5027-GN to see a logical high. The solution was to drop the supply voltage on the GRINCH to 4.6V DC and the MBI5027-GNs were fine. This will only happen with a very small number of PCs (and older laptops). Other uses have found that their MBI5027-GNs work fine with their PCs, without the need to adjust the GRICH’s voltage supply as they have a higher voltage on their LTP ports (closer to 5V).

David V. Fansler
06-06-2007, 11:39 PM
I found that if I used a 1.8k pull up resistor on the data 0 line and strobe line going to the input of a 74HC14 set the voltage where the schmit tigger would fire. You can see my schematic at http://www.dv-fansler.com/Computer%20Lights/Images/Olson-DVF-595.pdf
David

FireGod
06-07-2007, 12:09 AM
I found that if I used a 1.8k pull up resistor on the data 0 line and strobe line going to the input of a 74HC14 set the voltage where the schmit tigger would fire. You can see my schematic at http://www.dv-fansler.com/Computer%20Lights/Images/Olson-DVF-595.pdf
David

I also tried this on several laptops and it did not work on any of them.

David V. Fansler
06-07-2007, 04:03 PM
Ow! I have an IBM ThinkPad - your milage may vary????

I used an oscilloscope to determine the best value for my conditions.

P. Short
06-07-2007, 05:26 PM
There have been a number of different measures taken to solve problems with the 595 circuitry.

First, some people have discovered that the operation is sensitive to the parallel port mode in the PC. It seems that changing the mode (in the BIOS) seems to solve the problem. It's not clear why this works, and I have never heard of anybody putting a scope on it to solve the problem.

Second, I seem to recall people solving the problem by just adding pullup resistors on the control signals. Again, nobody has reported putting a scope on the controller to see what the exact problem is that was solved.

Third, some people have put pullup resistors plus the HC14 schmit-trigger buffer on the control/data signals. It worked for a few people, but not everybody.

Fourth, some people have solved a problem by reducing the supply voltage on the 595 chips (or whatever the chips are). This seems to solve their problem, but it is not clear how universal this solution is.

At one point in the past I used a scope to look at the signals coming out from three PCs (1 desktop, 2 laptops), and saw some different situations that may cause problems. Some of the problems were voltage level, which could have been solved by either using TTL-level chips or by reducing the voltage). But some of the problems were timing problems, where some of the signals had very long rise-times, to the point that they didn't reach final level before the next possible signal change.

The question arises, of course, as to why people are having so much trouble with otherwise perfectly functional parallel ports. The problem, I think, is that the parallel port is not being used in the manner for which it was intended. The original parallel port (and stuff that plugged into it) had TTL voltage levels. Most uses had feedback around the strobes (nSTROBE -> nACK), so that a slow signal or long rise time would only slow things down, not break them. Unfortunately, it's too late to fix some of these things now.

But what I would recommend when problems are encountered is:

1) Check all of the possible parallel port modes.
2) Add pullup resistors on the OC pins (1 and 14).
3) Either lower the controller voltage or use buffers with true TTL-level inputs on the three relevant signals (pins 1,2,14).

And even this may not make every parallel port work, because for some ports the software can drive the signals so fast that the waveforms are not right (unless some sort of extra s/w delay is created).

--

Phil

wjohn
06-07-2007, 05:35 PM
Phil

As always, you take the BS out of the discussion. Great post.

John.

rjanuary
06-07-2007, 07:02 PM
Wow, thanks for all the advice! I will look into these suggestions and see what works for me and post it.

Is there a common problem forum, or FAQ setup where things like this can be posted for future reference? I'm sure this question will surface again if its a common occurance.

Richard

P. Short
06-07-2007, 08:40 PM
This information should go into the wiki when it comes on-line.

--

Phil

Macrosill
06-07-2007, 09:09 PM
Phil,
Make a new thread titled FAQ and post the above. I will make it a sticky. Or I will do it with your permission.

P. Short
06-07-2007, 09:18 PM
You have my permission...although you might wait to see if anyone else wants to add something or disagree with something that I said (give that parts of it are just my opinion).

--

Phil

Josh
06-08-2007, 12:11 AM
hit it on the nail Phil, i had to run a pullup with my 12 channel, probably have to do the same this year for my 595 or grinch, whichever i get done

David V. Fansler
06-08-2007, 05:09 PM
Phil was elegant as usual with his summery of the situation, however my post just before his does point out that I did use an oscilloscope to observe the signals coming from the parallel port as I figured out what value pull up resistors to use. While not explicitly stated, I was also watching the output of the 74HC14 to see when the output signals were following the input from the parallel printer port.
David

RJ
06-08-2007, 09:03 PM
If you use the newer chips on the grinch this wont be a problem. Phil is dead on in that with lower voltage and slower rise times there isn't enough voltage or sometimes enough time to get to the threshold of what the chip sees as a high signal. With the new chips instead of needing .8 * Vdd to register as a high you only need 2 volts. this takes less port voltage and less time to rise so it solves both problems. Can't help with the 595 chips as I never researched any direct replacements for them with lower thresholds I'm sure they exist. Either the allegro or the newer chip there testing will work for you grinch problems. RJ

P. Short
06-08-2007, 09:24 PM
All of the Allegro parts that I have looked at (6276,6278,6279) seem to have a VIH of .7VDD (better than .8VDD, but not by much). The same is true of the one or two ST parts that I've looked at. Which parts are you referring to?

--

Phil

RJ
06-09-2007, 08:43 PM
The new chip that some of them were looking at that they posted the info on had a VIH of 2.0 volts I recommended they order a couple and try them but haven't heard anything more on it.

1-4-me-2
07-19-2007, 08:03 AM
I have always run my 64 channel 595 from a laptop. I use a 25 pin LPT to RJ45 and I get power from the USB port. The USB power is connected internally to the 25 pin adapter; signal and power are sent down 1 cable to the board. When I build my board, I used 8000 MCD Blue LED’s for the signal indicators (it is insanely bright). Only once did I get an excessive power draw message when I had all 64 channels pulsing on/off very fast.
The laptop is a P4 with 384 ram running Server 2003. There is no special video card in it, and it runs fine with preview. I also send audio out the headphone to a powered speaker

A Marchini
07-19-2007, 10:29 PM
Most uses had feedback around the strobes (nSTROBE -> nACK), so that a slow signal or long rise time would only slow things down, not break them. Unfortunately, it's too late to fix some of these things now.
--

Phil

Actually, why not use that as a solution.
Connect the strobe output to a in between circuit , with TTL switching, then loop that signal back to the ACK.
A few seconds of changes to the 595 plugin and this could be tested for many people.

-- Transition Strobe High
wait for High on ACK
-- Transition Stobe Low
wait for Low on ACK

Then you slow the clocking down to the point needed.
Use the paper out signal to monitor the latch output or something.

Tony

RJ
07-20-2007, 11:53 AM
Here is another way around it. see post
http://www.doityourselfchristmas.com/forum/viewtopic.php?p=2087#2087

waffles907
12-02-2007, 03:12 AM
Hello all....

I have a dell laptop computer and it has the 3.3 volt output and I am trying to build the 595. "I already have all the parts".. I have put one chip on a test pad and have tryed all of what you are saying and still not much luck... will the 74hc04 work for a driver??? and i have a power supply out of a old computer so the voltage is 5.1volts
what would be the best way to drop the supply voltage "if i really need to because I would rather leave it at 5 volts", and what size pullup resistors ... I tryed the 1.8 as suggested in one of the earlier post,,, I have tried all the diff bios setting and tried all the diff. program settings...

thanks wayne...

Macrosill
12-02-2007, 09:23 AM
What is the behavior you are seeing? Are you seeing random flashing of all channels anytime data is sent? Or are you seeing nothing at all? Are you using a coop board or a home etch?

waffles907
12-02-2007, 01:31 PM
I have a dell laptop and I had to put a 5v regulator "7805" on the 595's

I used a 74hc04 for a input buffer, to drive the 595's and put it into a peg board, "lots of wireing", but I seem to have it flashing the LED's, now I just have to test it with the triacs....

Thanks wayne