Dane.Kouttron

Display.Power.Supply

The connection terminal:          

As shown, the LCD variable is more or less a contrast type line where the negative voltage value correlates to a certain contrast.

Methods of making -15(ish) volts from your 5v line

        Make a simple inverter:                  

555 wiring:

Simple inverter: 

Using a pulse train from a 555, 3 common npn transistors (2n3904, 2n2222, or alike) and a pencil wound transformer its possible to make -15V with your +5v rail. 

How:

The first bottommost transistor acts as a crude inverter. when a logic 1 is sent from the 555 its output is ground. this is 180 degrees out of phase with the upper transformer input. together they pull down either side of the transformer at alternating intervals, making a crude ac. now the turns ratio on the transformer is in a 3:1 ratio so while the inner coil may be only 3 turns the outer would be 9. [The ratio is the same as the multiplication factor for the voltage. 

The last part of the circuit turns the ac to dc using a half wave bridge recifier (you could full bridge rectify for more efficiency). now check that it works and plug the positive output to your systems ground and the negative output is your - voltage for the lcd contrast. turn the 10K pot. to adjust contrast.

Or use the following schematic from www.sover.net                                  
                 

    

Use a 9V. 

If your in a crunch for time, plug the (+) lead of a 9V batt into your systems ground and use the (-) lead from the 9V as your negative voltage.           

The all electronics 256X128 lcd Info:

Product site: Here
Spec Sheet: Available here
More notes: Check the forum-type responses on all-elec if you have questions about the product

 

 

 

 

 

 

 

 

 

Dane.Kouttron
Rensselaer Polytechnic Institute 
Electrical & Electrical Power
631.978.1650