Ok, Im stuck

network_master · Post by **network_master** » March 22nd, 2009, 8:34 am

Hi all,

I've been searching all day, and im lost.

I pulled apart a Fermax door system that had a 2x16 LCD screen in it.

I wired it up using these instructions
http://www.overclockers.com.au/techstuff/a_diy_lcd/

Mainly because the screen looked roughly the same as the one i have.

Im not 100% sure what the model is.but it has 1602H on the back

Anyway, i wired it up using those instructions. I've double checked and tripple checked my wiring, i think its fine. I'm not new to soldering either, i'm pretty experinced. I havent reused a cable ive made a new one using a port and backshell. I'm not using a veriable resistor, but ive read you can make it work without it

So i plugged in the Molex connector into a PSU and the Parrallel port, powered it up, installed Port95NT and away we go? Nope!

I've got the 16 Black squares so i assume thats a good thing!

So i thought maybe that computer was the issue, changed to my IBM laptop - same thing, 16 squares, Port95NT no change when i run LCDsmartie

Bothi ports are onboard ports (Laptop and PC)

Im trying my laptop at the moment, Its running with IRQ7 and LPT Mode 378 and im using the latest release of LCD Smartie

So any help would be greatly appreciated.

Thanks guys

Post by **caesar** » March 22nd, 2009, 10:12 pm

Meh, that wiring is not compatible with LCDSmartie.
Smartie also needs the RW pin connected to the parallel port (that "connection list" you mentioned has LCD RW connected to ground).

Use the wiring schematics from here: http://lcdsmartie.sourceforge.net/circuits.htm

network_master · Post by **network_master** » March 23rd, 2009, 9:55 am

Thanks for that!

I rewired it according to the LCDsmartie diagram (without the backlight)

Same thing im afraid to say

There is one thought that comes to mind, is that im connecting the grounding ports to the molex ground and not LPT for ground.

Any other ideas?

Thanks guys

Post by **caesar** » March 25th, 2009, 7:58 am

You must connect the ground to LPT too...

network_master · Post by **network_master** » March 25th, 2009, 8:45 am

okey dokey

will try that now, i had a funny feeling that would be the problem

network_master · Post by **network_master** » March 25th, 2009, 12:05 pm

ok

Doing that worked, it allowed LCD Smartie to send a signal to the screen , i would see it, BUT! it had 100% contrast, so i couldnt read it clearly (barely able to see it)

I have a 20k pot and i tried to wire it in using that diagram, but it didnt work.

So any other ideas to try and help me out?

Thanks in advance

Post by **caesar** » March 26th, 2009, 6:14 am

The lcd could be a extended temperature version, in that case you may need negative voltage to drive it.

Try to find the displays datasheet to be sure how to drive the contrast pin.

network_master · Post by **network_master** » March 26th, 2009, 12:37 pm

Ok,

so i found the data sheet (helps if you google the manufacturer, my bad.

They are the same as the LCD smartie diagram.

So i stuffed it up so it wasnt working, then i got it working again but again with 100% contrast.

I had some 330ohm resistors laying around, i wired 6 of them in series and it helped, it dropped the background contrast down a bit but its still quite dark.

So i had a 20k pot (yeah i know i need 10 but i thought, what the heck)

didnt work at all!

Then i thought, jeez im a moron. These screens (i have 3, all doing the same thing so it must be something im doing) are off a fermax door system. I also removed the pot from the control board. With a multimeter, i ran a test to find what legs of the pot went to what pin. Wired it all up.... 100% contrast, adjusted the pot, same thing.

What i thought was really weird. Was if i lightly touch the ground wire to the contrast adjust pin its readable. But when i solder it all up.... 100% contrast.

So does anyone have any ideas what im doing wrong??

Obviously its an issue with resistance..... so can any one offer some help to what resisitor i need?

And if i ground the contrast pin it will give 100% con trast, but a few walkthroughs say to ground the contrast pin, and they show them working... what am i doing wrong!

And thanks in advance (especially to Ceasar) your help is greatly appreciated by this noob!

network_master · Post by **network_master** » March 27th, 2009, 2:15 pm

I got it working!!!!

I was wiring the 20k Pot the wrong way and the pot was dead, so im sure that wasnt helping....

Its all up and running now and it is awesome!

Thanks for all your help Ceaser, really appreciate it