Hello, i have LCD from old alarm, I think it's a 20x4 lcd. But problem is with connect this with Arduino. I know how connect when I have 16 pins I one row, but here are 2 rows for 8 pins, I read manual for lcd with HD44780 but I can't understand how connect with this I know about every pin this below list, but I tried every connection :
GND
Vcc - 5V
V0 - potentiometer
RS - command/data
RW - gnd
E - read/save
D0 - data
D1 - data
D2 - data
D3 - data
D4 - data
D5 - data
D6 - data
D7 - data
Vbacklight - 5v
GNDbacklight
Normally I use 12 pin 1,2,3,4,5,6 and 11,12,13,14,15,16, connect to Arduino and use library LiquidCrystal lcd(rs, e ,d4,d5,d6,d7) and this is working for lcd 16x2 but with this lcd is problem. I see light when connect to power but don't see anything I mean text. So any one know how connect this? Below I put three pictures
This may be an extended temperature range device in which case the voltage applied to pin 3 would have to be more than 5 volts below the supply voltage. In other words you may need a negative voltage at pin 3 with respect to GND.
First try this:
Connect the power and backlight (pins 1, 2, 15, and 16).
Connect pin 3 to GND. If you see two rows of boxes you have a 'normal' LCD and after you connect the rest of the pins your device should work.
If that doesn't work then you should try a negative voltage at pin 3. A small battery with its positive end connected to GND and its negative end connected to pin 3 will provide a simple way to test this out.
floresta:
This may be an extended temperature range device in which case the voltage applied to pin 3 would have to be more than 5 volts below the supply voltage. In other words you may need a negative voltage at pin 3 with respect to GND.
First try this:
Connect the power and backlight (pins 1, 2, 15, and 16).
Connect pin 3 to GND. If you see two rows of boxes you have a 'normal' LCD and after you connect the rest of the pins your device should work.
If that doesn't work then you should try a negative voltage at pin 3. A small battery with its positive end connected to GND and its negative end connected to pin 3 will provide a simple way to test this out.
Don
Ok second way it is correct. I used 9V battery and now I see the 2 rows of boxes. But now how can I set contrast ? Normally connect potentiometer to GND or what?
This display is fascinating for a couple of reasons. One is that it does not appear to have a LED backlight; if it is lighting when you apply 5 V it could even be incandescent lamps. You need to know how much current it is drawing and whether your 5 V supply is being pulled down to a lower voltage by connecting it.
The second is that it has a different contrast ladder - almost all current displays use 2k2 resistors, this one used 510 Ohm resistors. You would not be using a 10k potentiometer to control it - and you should never connect that potentiometer to Vcc in any case. Testing as floresta says with pin 3 grounded would be appropriate; if you need to use a variable resistor in series, a 1k would be the one.
All this begs the question. Obviously the very first step would have been to fully examine the circuit in the "old alarm" from which this was removed.
arkoo94:
Ok second way it is correct. I used 9V battery and now I see the 2 rows of boxes. But now how can I set contrast ? Normally connect potentiometer to GND or what?
Two rows of boxes? OK, so it is a 2004 or even longer display.
A 9 V battery is likely too much. floresta meant a 3 V battery.
You need a second 5v power supply connected as shown in figure 21 of the Hitachi HD44780U datasheet. The point labeled V5 is pin 3 on your module.
Basically the positive terminal of this supply gets connected to GND. The negative terminal gets connected through a variable resistor to pin 3. You can use 2/3 of a potentiometer as the variable resistor.
floresta:
You need a second 5v power supply connected as shown in figure 21 of the Hitachi HD44780U datasheet. The point labeled V5 is pin 3 on your module.
Basically the positive terminal of this supply gets connected to GND. The negative terminal gets connected through a variable resistor to pin 3. You can use 2/3 of a potentiometer as the variable resistor.
Don
After 5 days finally I done this. This LCD is using in fact negative voltage for VO. I measured and text display between 4.5 to 3.3 v, I used battery 9v and 2 resistor 2k and 470 ohm and set power to 3.95v and is working. Ofcourse first 5v connect from Arduino and second from battery I know I can use lower like 5v but I had in home 9v so ..
