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How to hook up backlight on CFAH1602C-YYH-JP

gamfa

New member
We have a CFAH1602C-YYH-JP display hooked up in a tachometer circuit for a diesel engine and we can't get a good grip on how to hook up the backlight. Some posts on this forum have given me a start but I would like to be sure of what I'm doing so I don't burn something.

The Specification Data Sheets refer to pins 15,16,A & K when referring to the backlight. On the "Contour Drawing & Block Diagram" sheet on the contour dwg. there are 4 pins shown on the right side of the display. The top one is called "A" and the bottom on "K". Are these the A and K pins that service the backlight?

For the sake of my questions, I'll assume I'm right on that point at least.

On that same sheet toward the bottom they give 2 small block diagrams on the hookup of the backlight. Looking at the top one called "Drive from A, K" it appears all we need to do is pick up the 5V off the line that feeds pin 2 (VDD) and run a wire to the "A" pin on the opposite side with the right resistor to give us 4.2v to 4.6v on pin "A". Then run a wire from the "K" terminal to the ground side of the display, pin 1 (VSS). Am I right here.

The second method uses pin 15 for the 5V and 16 for ground. What puzzles me is the show 2 resistors. Anyone know why 2. Does the 4.2v to 4.6v spec. still apply in this method? Below this second diagram they have the following...

(Will never get Vee output from pin 15)

Duuhh....what is that telling me? Is it something I should consider in choosing a method to hookup the backlight?

Would one method be better than the other. We have bench tested the tach and it works like a champ but I hate to have to drive down the road at night with a mini Mag light stuck in my mouth to be able to read the tach.

Thanks for any help..
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CF Tech

Administrator
For the CFAH1602C-YYH-JP:

Rled = (Vdd - Vled) / Iled

Rled = (5v - 4.2v) / 0.13 A

Rled = 6.15 ohms minimum

So something like a 10 ohm will work fine.

Just go like:

+5v to resistor to A

K to ground
 

gamfa

New member
Thanks,,I guess then that the rest of my post is correct? I can pick up power ahead of pin 2 and ground back to the line off pin 1 or use pins 15 and 16?
 

CF Support

Administrator
You are factually correct.

If you move the 0 Ohm resistor from J16 to J1, you will make your pin 1 to K connection.

If you remove the 0 Ohm resistor from J15 and close J2 with a 10 Ohm resistor (like CF Tech suggested) then you will connect a current limited +5v from pin 2 to A on the backlight.

Hope this helps.
 
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