LCDInfo.com

no that's with load.. without load I got like 0V.. strange i think..

what should i use to boost my voltage at my LPT pin 7 then?

btw.. can I use 74AC245 or 74HC245 instead of 74CLX245 or 74LVC245?

Are you sure that the LPT port pin was driven high when you measured 0V ? The PCD8544 driver drives pin 7 high when it's selected and LCDInfo is running. When LCDInfo is closed PCD8544 driver takes pin 7 low again.

It's also possible that your parallel port isn't able to source enough current to power the lcd and that's why voltage drops.

Possible variation of the schematic presented in this thread would be to power the regulator from some external source instead of LPT port pin 7 and then route the LPT port pin 7 to one of the 3 unused inputs of the 74LCX245 and also route the lcd V+ pin to the corresponding 74LCX245 output. The reason doing it this way instead of wiring the lcd V+ straight to the regulator is that according to PCD8544 datasheet a proper startup sequence must be done just after powerup to not damage the display and this is only possible when the LCDInfo driver can control the V+ line of the lcd.

You could also control the V+ line using a transistor or fet but I think 74LCX245 outputs should be able to source enough current so there wouldn't be need for extra parts.

I can't recommend 74HC245 or 74AC245 because they're not spec'd for 5v input logic levels with 3.3v operating voltage.

okay..
I think I got it.. but then I need something to get my voltage a bit higher than 2.15..

what component would you recommend to like boost it up 1.5 or 2?

The 74LCX245 would work as the buffer/booster in the connection I described in my previous post.

If the parallel port voltage drops because it's not able to source enough current then adding anything there without external power source would only make things worse.

But before deciding what to do you should first figure out what your parallel port outputs without load.

I digged in my box for my multimeter and found it :)
my output without load now is 0.14 and with load 4.23 on pin 7
on pin 1 it's w.o. load 4.23 and w. 4.27

Your voltage without load on pin 7 is still strange. So this is without anything connected to the parallel port and the pin driven high by software ? Your other voltage readings look fine. It's still possible that your parallel port is not able to source enough current to drive the display and circuit.

henri:
got my display working..


thanks anyway..

yes my voltage is a bit strange on my pin7.. but who cares?


-------------------
ADMIN EDIT:
jetage reported me that his display died using this schematic. So others might not want to try this one.

Glad to hear that your display is working. Looks like you then decided to just connect the LPT port pins to the display inputs without extra level conversion. Like I mentioned in some of my earlier post in this thread it should work but it's possible that the display doesn't like it in longer use. But it's not very expensive display after all.

A little addition to your connection could be some current limiting resistors to the data lines (lpt 2-6). Maybe few hundred ohms or 1Kohm or something like that.

I think it's like you said..

What if I add the resistors then?
Will it work for longer or do you think the lifetime will be the same?

they will protect the lpt lines ... nothing more

Also the resistors should limit the current flowing from lpt port pins to the lcd pins.

But I can't say anything definitive of how well it would work as I've only tested it the way described on the first page of this thread.

how much ohm do u have , so u don´t burn ur nice lcd it´s fantastic , keep up the good work

I don't have any ohm as I don't use resistors. I'm using the 74LCX245 chip for the logic level conversion.

hmmm okej. I follow jetage schema :p , how much ohm do i need

Maybe 1kohm. But I've never tried this so I can't give any quaranties how it will work.