Electronics parallel LCD help...

so somming like this:

http://www.maplin.co.uk/Module.aspx?ModuleNo=2200&TabID=1&source=15&WorldID=3&doy=12m12

 

yes, fine.

You should be able to use the cheapest type of pot, because there is so little contrast.

 

ok ive brought a 10K pot.. i have hooked the middle pin to pin 3 on the LCD and the other 2 pins to the 5V and ground... now ive turned the dial both directions and nothing has happened.. all i get when i turn it towards the 5V pin it turns off and comes on when i turn it the other way...

 

okay were i said

contrast, i ment current, my bad but thats not the problem.

So when u turn the pot toward 0v, do u get all the LCD segments turning dark? If so turn it so its *just* before they all start becoming grey (or when they are about 1/4 grey). Then try hooking it upto the computer.

 

i get zilch... it just stays green...

 

okay check your wiring.

0v, to GND, 5v to 5v. Vo to the "sweeper" of the POT, the other to legs to 0v and 5v respectivly.

there is a problem with that wiring.

Make sure u have PIN1 the right way round. (ie what u think is one, isn't sixteen)

 

here is a pic of the circuit.. ive labeled which wires are which on the pot..

 

erm when i look at ur pic, i see lines 14 and 13, going towards power. This might be the picture, or the mass of grey wires getting to me, but that shouldn't be, 13and14 should be the high 2 bits of the 8bit data.

pins 1 2 3 are all u need to worry about testing right now.

 

13 is going to 5V and 15 is going to ground..

the way i read it is that L+ is pin 1 and went on from there

 

There is your problem then. Pin 1 in the pin with the little 1 above it (two pins to the left of L+). Pin 14 is the pin with 14 above it.

Ignore L+ and L- for now, they're just for the backlight.

The three pins next to L+ and L- are for the supply and contrast.

 

lol... silly old me.... i knew were pin 1 was.. but i thought it was the way the board was made

 

Hopefully the LCD hasn't been damaged. Let us know how you get on.

 

so i want to wire it up something like this



to start off with (if u understant the picture..

 

ok i cant get it to work.... i redid it so that pin 1 is ground, pin 2 is +5V and pin 3 to contrast... i connected pin 3 to the middle pin of the pot and the other 2 wires to the other 2 legs i also connected the back light aswell... but it no worky...

 

Your diagram has the polarity wrong for the supply leads, but you describe your wiring the correct way.

If you get no test pattern with ground connected to pin 1, 5V connected to pin 2 and the pot correctly wired then it sounds like your LCD could be damaged or not working.

Note that if you did connect it up as you drew it in your diagram before swapping the 5V and GND leads round, then in all probability you damaged your LCD from that.

 

yer i realised my diagram was wrong when i was checking the circuit over...

but i dont get anything when i turn the pot either way...

 

if you plugged this upto a computer, while you were putting power on the data pins only, its VERY likely you killed the display and also you port.

Just focus on the GND 5v Vo

(Vo been operating voltage, the contrast voltage).

Read-re-read and read the datasheet, been serious when i have dislexic/stupid **** problem, turning my laptop (PDF reader) upside down, and reading it again upside down often makes me see what i'm miss reading.

if you can get it so when u fiddle the pot, you get black rectangles, its either dud display or ur missing something, can't break it down much more than that.

 

when i redid it starting from pin 1 on the board and not the backlight pins i had cut off all the wires going to the parallel port... but b4 that i did have the wires connected to the parallel port...

 

see if you have anything else you can test your parralel port with

 

i dont actually have anything that has a parallel port on it