Help with wiring on parallel LCD

Halo · Post by **Halo** » May 21st, 2005, 12:19 pm

Ok well i have a nice 4x40 lcd. I have wired it all up and it works but i have connected the backlight to 5v through a molex connecter which works, but i want to be able to turn the backlight on and off using lcd smartie. Is this possable ?

On the ccts page the 3rd image seems to maybe show some thing that will be able to do this ... with the BC547 transister that is connected to pin 17 and to ground of the backlight. I would have to get the electronics textbook out to see how that would act as a switch...

But basically what i want to know is about that pin17. When i go to commands>backlight off and click that will that make pin17 high (3,3v) ?

If so can i then use an AND gate to control the backlight, with the 2 inputs pin17 and the other 5v and the output connected to the backlight vcc?

I see that pic uses to control ground and not vcc but i would rather have a constand ground and cut the vcc to the backlight...

any suggestions are welcome about what i have thought up

Post by **limbo** » May 21st, 2005, 2:49 pm

I never tried the wiring on this wiring .

First of all you have to check the pin 17 on your parallel port for voltage switching, depending on the command of LCD Smartie. The voltage there must toggling between high and low levels

See below

The BC547 its a typical NPN transistor amd must working if the voltage on base follows the refered values

For more info about BC547 check the pdf provided by Philips
http://www.ortodoxism.ro/datasheets/phi ... _547_3.pdf

I'll give it a try with the fist opportunity.

GOOD LUCK

maltone · Post by **maltone** » June 15th, 2005, 7:48 am

has somebody tried it ?
i use a little different diagram and can manage the backlight with other lcd programs but not with lcd smartie.
this diagram i use. it is an 4*40 lcd.
http://www.jalcds.de/images/4x40backlight.gif

Post by **limbo** » June 15th, 2005, 6:14 pm

As I can see on schematics U are using pin 15 instead the pin 17 on lcd smartie schematic,
this must be the reason that LCD smartie cannot control your LCD backlight.

Why don't you try it?

maltone · Post by **maltone** » June 15th, 2005, 6:53 pm

i don`t try it because pin 17 is for e2 (4*40 lcd) and the diagram is for an 4*20 lcd. i don`t want destroy my lcd .....

Post by **limbo** » June 26th, 2005, 8:56 am

A user of LCD Smartie (DIEGO) reported that the backlight feature is working

please refer to http://forums.lcdsmartie.org/viewtopic.php?p=794#794

maltone · Post by **maltone** » June 26th, 2005, 7:43 pm

thx, i will use the diagram.