MPGuino mod for enhanced temperature range LCD

[AndrzejM]

When I was planning to install my MPGuino and put display into an instrument cluster I wanted to install the smallest LCD I could find. So I bought 53x20mm LCD with enhanced temperature range. After mounting everything I've noticed that contrast is way off the level it should be. So I've started digging and found info that enhanced temperature range LCDs have contrast driven by negative voltage. I hooked up a small battery to provide negative voltage and everything started to look as it should be. But that wasn't the best solution so I decided to build a simple charge pump inverter. It works like a charm.

All you need is a few elements worth less than a soda can.
Schematic diagram:


Parts list:
2x BAT48 - Schottky diodes
2x 2uF - low ESR capacitors
1x 10uF - low ESR capacitor
1x 10k - 0.125W resistor
1x 4k7 - 0.125W resistor

The best thing is that you can still adjust contrast using MPGuino setup screen.

[nickdigger]

Do you have a pic of the LCD module? I'm wondering if it has a ton of wasted space, like every typical 2x16 or 4x20. It seems like the only LCDs that don't have a huge circuit board are the graphic ones, which are overkill for this project.

Right now, I'm using a 4x20, and half of my warning lights are blocked (!) I want to keep it at my instrument cluster, so my only other option is to block the Tach.

edit: I just found a 4x20 with minimal wasted space, but the overall size is still huge. I guess the circuit board is still big, but the viewable LCD is much larger now, covering it all.
http://www.ebay.com/itm/20x4-2004-La...-/170746889006
It also costs 3x more than a regular 4x20, and about 2x a graphic w/touchscreen, so forget it.

Originally Posted by AndrzejM

All you need is a few elements worth less than a soda can.

When I read this, my first thought was an empty soda can, which is about 5 cents at the recycler.

[AndrzejM]

Originally Posted by nickdigger

Do you have a pic of the LCD module?

LCD

Originally Posted by nickdigger

When I read this, my first thought was an empty soda can, which is about 5 cents at the recycler.

5 cents... It's plausible