CFAH2002A-TMI-JT Customization

[Yves_caf]

My company bought a sample CFAH2002A-TMI-JT for testing. I'm working to get it working for our application.

We use a 14 pin header connector on pins 1 to 14. We don't use pins 15 and 16 (backlight). To light the backlight i added a jumper on J1 and a 50 Ohms resistor on J2. 31mA of current in the leds, nice glow, below the backlight specs, works good.

Next, our controler PCB is sending a fixed voltage for contrast. This voltage is around 0.46V and not resulting in a nice contrast on the CFAH2002A-TMI-JT. I would like to add two resistor on the display PCB directly to set the contrast. Is it possible ? Where should i put the resistors ?

I would like to know if it is possible to have the displays customized for future quantity orders. Resistors for backlight and contrast already added by Crystalfontz. And connector, could you add it for us ?
We use a 3M D2514-6002-AR or 3M 30314-6002HB. Our minimum order quantity will be 100.

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[CF Support2]

For setting up your modifications, which will lead to a semi-custom part I am creating a ticket in our support system. You should get an email stating we've created a ticket, and we'll continue the definitions there.

 

[CF Tech]

Using fixed resistors for the contrast can cause trouble.

The contrast voltage may need to change depending on:

1) viewing angle
2) operating temperature
3) operating supply voltage
4) LCD material changes or polarizer changes
5) LCD controller substitutions

It is better to have the contrast controlled by a DAC, or potentiometer . . . or some way the end user or at least final QC can tweak the contrast to the optimal setting.

Please check the thread here:

https://www.crystalfontz.com/forum/showthread.php?p=27001#post27001

Sometimes very long runs of modules will be bang-on at the exact same contrast level for a very long time

Other modules will seem to need tweaked batch-by-batch and module by module

You would probably be safe with fixed resistors, just be prepared to change them as needed in final assembly.

We have a little circuit that we use, which takes a PWM output and generates the variable (positive or negative) voltage which can control the contrast. Please see the spreadsheet in this zip file:
http://crystalfontz.com/backlight/PWM_Neg_Voltage.zip

I have another 2-stage version that works lower voltage inputs, or would probably also work for larger negative output.

Here is another one I came across, have not used it but it is probably similar:
http://www.piclist.com/techref/microchip/pwmvee.htm