need simple 5v ~50Hz AC ouput for LCD

Thread Starter

elRey

Joined Feb 23, 2009
65
Hello,

I have an unknown 4 segment (clock) LCD that was driven by a PCF8576CT. I've located the four baseplates and now need to identify the common segment pins for the LCD. So I just need a simple circuit I can use the output to discovery, thru trial and error, the segment pins on the LCD.

i.e. touching one lead to one baseplate and then touching the other lead to each of the other non-baseplate pins and noting which segments activate.

Thanks,
Rey
 

Thread Starter

elRey

Joined Feb 23, 2009
65
Thank you. That will give me a 0-5v wave. Now how do I get a -5v to +5v wave?
 

beenthere

Joined Apr 20, 2004
15,808
If you have the +/- 5 volt lines, run the 555 with -5 to the ground pins and +5 to the positive ones. That should give you the +5 to -5 pulse.
 

Thread Starter

elRey

Joined Feb 23, 2009
65
Ah, I don't have the -5v line. I'm testing on a Electronic Lab with +1.5v, +3v, +4.5v, +6v, +7.5v, and +9v lines and gnd. How can I create a -5v line?

Thanks again for you help.
 

Bernard

Joined Aug 7, 2008
5,252
Is the display ground floating? If it is , might connect two resisters,around 1k, in series from 555 output to ground, and use center as ground, boost 555 operating V to 10V. Should then have +5 &-5 square waves refferenced to center tap.
 
Top