is this display suitable for my midibox sequencer?

[hazes]

Hi,

I searched the forum and the wiki, but since i'm a complete beginner at this, i'd really appreciate some expert-advice on my choice of display  :). I found the following display, but i'm not quite certain wether it's ok.

http://www2.produktinfo.conrad.com/datenblaetter/175000-199999/181659-da-01-en-LCD-MOD_STN_BLAU_NEG_LED_WEISS_40X2.pdf

Thanks for your reply and i'm really sorry if this question is asked before.

[TK.]

Hi Hazes,

yes, it's perfect!

Best Regards, Thorsten.

[hazes]

thanks! I think I'll go for the blue ones :)

[hazes]

one little question  :) The data-sheet of the LCD tells me the led needs 4,2V on it's anonde. The Core-module delivers +5V on the B+ connection. Can I just connect the two of them, or will I damage the LCD because of the higher voltage? If so, what can I do to drop the voltage by 0.8V? Put in a series-resistor of ?-Ohm?

[hazes]

I think I just answered my own question :)

(5-4,2)/0,06=13,3

I'll just buy a 13 Ohm resistor and solder it in the right place.

OT: I just saw the backlight on for the first time. Awesome!

[Wilba]

The Core has a circuit for controlling LED backlight current, it is usually connected to pins 15,16 of the LCD as per diagrams. Why don't you use this?

Second, the white LED is 3.5V forward voltage... typically white LED backlights are only on the edge, not an array all around the LCD... hence the two different forward voltage specs (3.5v and 4.2v).

SO I suggest you double check that 13 ohm resistor! You might be powering the white LEDs at 115mA!

[hazes]

Thanks for replying Wilba. Just to make sure I soldered a pot between B+ and the anode pin for the backlight on the lcd. When powered on, I slowly decreased te resistance on the pot until my volt-meter indicated 4,2V, which is the voltage needed to power the backlight according to the data-sheet (measured between Vss and LCD anode pin). I then measured the resistance on the pot and it was about 12 Ohm. That means that a 13 Ohm resistor (which I calculated) should be okay, shouldn't it?

[Wilba]

In that datasheet, the asterisk next to the "A" in the pinout is matched with the asterisk next to the "LED weiß Voltage", indicating that when it is a white LED backlight (i.e. white on blue LCD, etc) then you only need 60 mA and the voltage drop is 3.5v not 4.2v.

I'm no expert either, I'm only highlighting a possible mistake... and it wouldn't hurt to use a bigger resistor, whereas you might burn out those white LEDs if you use one too small.

[hazes]

I overlooked that completely! Thanks very much! The right calculation is:

(5-3.5)/0,06=25

Thanks again!