I'm working with an Arduino Duemilanove and a Z-4170 LCD identical to a Hitachi 44780 (apparently this model should be able to work with the arduino unit).
I've been following along with an LCD guide attempting to get an image to display on the LCD. Wired up and ready to go i uploaded the example Hello World app the arduino, only to find no image was displayed.
I checked the voltage across the 5V pin to ground, and found i'm somewhere around 4.2V, the manual for the lcd says i require at least 4.5V to have the LCD function.
Does this under voltage occur commonly? I'm unsure if i can raise the output voltage of my usb ports, or if i require an external power supply for this project. Any advice on the dilemma would be very greatly appreciated thank you!
You should measure the +5vdc pin with the LCD display disconnected. If it then reads the proper value then you know that the display is drawing too much current from the USB port. There is a limitied amount of current you can use externally to the Arduino board. Possibly you have it wired improperly causing too much current draw?
You can also try powering the Arduino board via the external power jack via a wall wart DC power module and see what the +5vdc terminal reads with the LCD connected. There can be more +5vdc current made available when you use the external power input.
Do you know what the current requirement specification for your display is?
Yes that is too much current to draw from the Arduino when using USB power. It is also right at the limit of external power current I would think.
may have to use a seperate +5vdc power supply to power the LCD display if it indeeds needs 1+ amps of current. It must be the backlighting that sucks that much current.
Ah i see, so if i get myself a power supply for the lcd i can switch it with a relay perhaps from the arduino, and just run all my signal cables from the arduino to the screen?
Thanks for your help retrolefty! i'll go shopping soon for the power supply
One very important thing to notice, is that you should remember to connect at potentiometer to the contrast pins on the LCD. On many LCD displays you cant see the image if the contrast is turned all the way down.
Does your display have back light ? if so you might have (read likely have) to put a current limiting resistor in the power connection to the backlight. Othervise the LED(s) providing the backlight will fry. Some displays already has the resistor built in.
THe guide i was using (Arduino Tutorial - connecting a parallel LCD) spoke about the pot. I'm using a 10k pot, and have tried adjusting the pot to get any image change. I'm using an lcd without the back light. Hmm, yeah i think the grounds are correct the guide also spoke about grounded the read/write line so i've done that. I'll see how it goes once the shops re-open. Thanks guys!
