LCD 16x2 HD44780U on 3V pic Directly?

[ngeronikolos]

Hello to everybody,

I have a PIC 16F628 running on 3V DC(battery).Can we drive 16X2 LCD MODULE (HD44780) lcd by micro on 3v directly? or we need to put level shifter??\

Thanks
Nikos

[Acetronics2]

Hi, N'Geron

I think this subject has already been treated ...

http://www.picbasic.co.uk/forum/show...highlight=3.3v

But that's just a part of the SEARCH

Alain

[ngeronikolos]

Thanks Acetronics for the link,

BUT i do not want to change the LCD.
Does it works or not???

Nikos

[ngeronikolos]

The data lines of the display work also with 3V signals????

[Ron Marcus]

The data lines will work at 3 volts just fine. The tricky part is supplying the module with 4.5 to 5Vdc at a couple of mAs. I did this for a low current LED backlight by using the hardware PWM module, a couple of diodes and two capacitors. If you need to shut the module down, then it will cost you two port pins. If not, you can use your PWM pin, and the 3 volt B+ line.
The general priciple is a diode doubler. You have a steady B+ of 3 volts, passing through a low loss schottky diode. Your PWM pin is attached to one leg of a 10 uF capacitor.The other lead of the capacitor is attached to the cathode of the first diode. Another diode's anode is attached to this junction, and the cathode of this diode becomes your boosted B+ line out. It is smoothed with another 10 uF cap to ground.
When the PWM pin is low, the first capacitor is charged through the first diode to B+. When the pin switches to high, it takes the leg of the capacitor it is attached to, to 3 volts. This takes the other side of the cap to almost 6 volts! It then discharges through the second diode into the smoothing cap and your LCD. You can do a software PWM, if you can't spare a hardware PWM pin, and just run a square wave at 12KHz or so. Look at the Maxim site for switched capacitor doubler ICs. It's a good tutorial for the basics.
Ron

[Acetronics2]

Hi, Ngeron

Browsing the datasheets I have here, it comes out 5v supply LCDs need :

supply voltage : 4.5 to 5 v
Input High level : 2.2 v
Input Low level : .6v

that means AS RON WROTE that Your LCD WON'T WORK @ 3v supply ..., but can be interfaced with a 3.3v supplied processor, with a separate supply.

Alain