how to build a -2,6 v (lcd negative contrast )with the 5v core psu

[boops]

Hi,all,i am looking for a shematic to build a -2,6 v(lcd negative contrast ) with the 5v core psu,thanks

I 've a made a newbie error when i 've ordered my 2 lcd at voti..be careful lcd 14 is not the must, take lcd 22 Boops

[boops]

Ping has given me this link http://www.modthebox.com/lcdhowto.shtml

thanks but how can i have 2,6v ?

[/tilted/]

The LCD derives its contrast voltage using a pot (P2) connected across +5V and GND (Vdd and Vss). The wiper of the pot is then connected to the Vo Contrast pin on your LCD.

Normally LCD contrast voltages are in the range 2V - 3.5V.

To get -2.6v, build the circuit linked by Ping, and wire your pot (P2) across -5V and GND. The wiper of the pot connects to Vo as normal.

Be sure to disconnect the +5V terminal of your pot before connecting it to -5V, to avoid smoke...

[stryd_one]

Also there are several hits using the search terms I gave you last night of schems using a 766* ICs

http://www.midibox.org/forum/index.php/topic,3540.msg23987.html#msg23987

[boops]

thanks folks

[ping-]

Ping has given me this link http://www.modthebox.com/lcdhowto.shtml

thanks but how can i have 2,6v ?

Uhmn..i didnt give you that link :)

I dont know who did, but it wasnt me.. i have never seen that link before :D

[boops]

::) sorry it's doug W.

[boops]

hi,i do the job... :o  it works ;magic electronic!!! An advice: put the trim p2 on a separate veroboard with the IC 7660 and Caps; be careful with the caps polarity and put off the 18F452...now i attack the opl3 -core connections  :P Good night and best regards .

[stryd_one]

[me=stryd_one]does the "it's working" dance[/me]

boops I hope you can share more details of your solution... you're not the first to have this problem, and I'm sure others will be in the same situation again  ;)

[/tilted/]

Good to hear.

Well done.

[boops]

stryd i 've done exactly that is wrote on the post and use a little my brain ,a paper and a pen too;)

f

[boops]

more explanations:

-printed the shema with the IC 7660 ,and caps

-buy the parts,don't forget the ic socket for the 7660 (or equivalent)

-pull off the ics of the core

-cut a little piece of veroboard and make a hole (3mm)to install on one hole of the core pcb

-desolder with (pompe a dessouder) the P2 (trim on the right on the core,which control the contrast)

-build the shematic http://www.modthebox.com/lcdhowto.shtml be careful with caps polarity ,take the +5v and ground on the core where the P2 was soldered,test short cuts,and polarity ,you should have -5v beetween ground and pin 5 of the ic 7660

-ok ,courage ,now solder the P2 on the little veroboard and see the  shematic below:

                                                                                                               

-control the negative voltage with the P2 trim..

                            BRAVO      Boop's

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