Hi, i was wondering whether a standard 9v square battery will be able to power up the Hitachi HD44780 which would consume 25mA to 50mA?.

 

Most LCDs draw almost nothing. It's the backlight that needs current. Your display will need 5V so you'll have to add a regulator.

 

ayane,

A standard 9V battery is good up to 25mA but definitely not 50mA. Besides, I doubt the 9V battery could keep a constant 25mA for a very long time. I would advise that you use the LM317 voltage regulator which can supply up to 1.5A.

Austin

 

I bet a NiMh rechargable battery would be happy with higher current than the alkaline if that is an option. 250mAh ones can be fairly cheap.

 

Put a push button on the back light circuit, so you can use it only when needed.

 

thanks for all the advices..i will take note.

Actually i using a pic18f452 to program the lcd. The lcd is a hitachi HD44780. I am regulating the 9v to 5v using a 7805 to power up the lcd.

LCD:
pin1 and 3 i connect to ground.
pin 2 to the 5v supply.

pin 6 ( enable) connect to RA1 of the pic
pin 5 ( R/w) connect to the RA2
pin 4 ( Rs) connect to RA3

pin 11- pin 14 connect to RD0 to RD3.

i supposed i did not use the back light. I employed a switch between the regulator and the battery. The main purpose is just to display some information for the user to see.

 

LCDs with backlights are often very hard to see with it off. Reflective LCDs offer very good visibility in normal lighting.

 

Not that ayane will ever encounter this problem, but here's just a little reality in modern LCD problems. The tough problem with cell phone manufactures these days is to have an LCD that will still be brightly visible under direct sunlight. As you can imagine, this is very difficult, especially considering the strength of the suns rays.

Austin