Hi Steve,
PIN Symbol Level Function
1 VSS - GND(0V)
2 VDD - Supply Voltage for Logic(+5V)
3 V0 - Power supply for LCD <-- A pot between 5V and GND with the wiper
connected to PIN 3 works well. The contrast can be changed as temperature
changes.
4 RS H/L H: Data; L: Instruction Code
5 R/W H/L H: Read; L: Write
6 E H/L Enable Signal
7 DB0 H/L <-- not used
8 DB1 H/L <-- not used
9 DB2 H/L <-- not used
10 DB3 H/L <-- not used
11 DB4 H/L
12 DB5 H/L
13 DB6 H/L
14 DB7 H/L
==================
15 A - Backlight Power (+5V)
16 K - Backlight Power (0V)
These connections should have a current limiting resistor added in series.
At least on the ones I have used in the past. Actually a pot here helps to
adjust the brightness as needed with a series fixed resistor.
I added a portion of my schematic. I don't show the VO circuit or the
backlight circuit either. I have a simple pot for VO. I think my pot is 20K.
I am thinking my data sheet actually had a current listed for the VO pin.
I usually control the backlight with PWM (contrast too) but it seems a bit
overkill here.
You will want to limit the current to the backlight LEDs.
The Vf is 4.2 for the Y-G version.
So
5.0V - 4.2Vf = 0.8V
0.8V / 0.180A = 5 ohms (rounded 4.44 to 5)
A 5 ohm resistor in series with the backlight LEDs should keep it safe.
The Vf is 4.0 for the WHITE version.
So, 5.0V - 4.0Vf = 1.0V
1.0V / 0.030A = 33 ohms
A 5 ohm resistor in series with the backlight LEDs should keep it safe.
So depending on which model you find, either a 5 or 33 ohm resistor should
keep the backlight in action.
In you want to dim it further, then a pot in series with your other resistor
can decrease the current (light output) without allowing you to overdrive
the backlight.
I also added pictures showing my additions to the Tracker2. And there is one
of the LCD in action.
Best regards,
Fred
