Thread: So i got a 40x4 off ebay...

No problem.

It does have a backlight, but you only ever notice it at night. It looks fine at night, perfectly readable. Infact the pics of the LCD in this thread when it was out the car were taken when it was pretty dark, if I remember correctly.

I know this thread is old... but i am having a problem similar to mikehunt79's...

I too have 4x40 lcd (Kl SN102 94V-0)... and i tried connected it with the diagram above (first post) minus pins 17 and 18 and the 10k pot...

However i have a backlight...and there are two pins on the opposite side of the 16 pins that i have not connected....

Do i need to connect the backlight up???? For the contrast i just connected pin 12->13...which is suppose to set it at max or something i believe..


here is a quick MSpaint diagram of what the back of the lcd looks like -
http://www.patmedia.net/daveoskin1/lcd-diagram.JPG

also.. if i do try to connect the backlight...is there anyway i can do it without the pots???

12->13 will set it to max or to Min don't know for sure.
But i believe that it is better to use the 10K and set it at about 75%.
You should see some bloks if you look at the lcd.(mine whas the firts row)

And you don't have to use the backlight if you don't whant to.
The ones you "highlighted"in your drawing are the ones for the backlight.
The one marked with the + is pin 17. the one with - is pin 18.

Originally Posted by peter3

12->13 will set it to max or to Min don't know for sure.
But i believe that it is better to use the 10K and set it at about 75%.
You should see some bloks if you look at the lcd.(mine whas the firts row)

And you don't have to use the backlight if you don't whant to.
The ones you "highlighted"in your drawing are the ones for the backlight.
The one marked with the + is pin 17. the one with - is pin 18.

yea the problem is... neither one appears to be marked + or -... or anything else...

I also just realize that i soldered all the cables wrong.. (i was soldering the parallel cable to an ide type cable [which goes to the lcd leads]..and when i connect the ide cable to the lcd... the wires didnt go where i thought they where going to go... )

so i cut all the crap off the ide cable.. and i am going to solder everything again according to this - http://www.markuszehnder.ch/projects...controller.gif



Do you think i can connect the backlight up without a pot? if so ...which to wires should be soldered together? or if i wanna try to do it with a pot... what kind???

Can you just connect +5v and -5v(GND) from the psu to the backlight????

here is what the back of my lcd looks like again - http://www.patmedia.net/daveoskin1/lcd-diagram.JPG

DON'T use +5V AND -5V together that will be 10V.
Use +5V (red) And GRN (black) from the PSU.

Conect the two to the backlight, if it doesn't light up switch the two around.
Since the backlight is made out of leds, it will only work if the curent goes in the right way.
Take the inner two for the backlight, or the outher two.(thats on mine )

For the backlight you do not need a pot, but it could be helpfull somethimes.

o yea, thats what i ment...

I also re-wired the ide cable.. but still no luck... i might have fried the thing...
So i guess all i can do know is either try the pinout mikehunt79 said that worked for him... or..... i dont know...


I just connected the backlight to the psu (the red and black wire from the floppy drive power thing) and it worked... althought im not sure if thats means anything (i guess the backlight will work even if the controller is fried..)



I just re-wired it AGAIN, using the pinout mikehunt79 did..... did basically the same thing...except it did not appear to get as hot.. just a little warm...
nothing on display... just the backlight...

Could soldering the contrast wire to the gnd wire (on the lcd) have set the contrast all the way down (so i cant see anything)???

It could be.
At the moment i don't have a lcd by hand.
But when i do i test it and let you know

Alright , thanks man...