Baby's First LCD

[muzza]

Ok, I just received my CFAH2002A-YMC-JP 20x2 module and now I need to think about wiring it. I found lots of useful stuff throught the forums, most of which I have printed for more detailed review. This leads to the following questions:

Backlighting: most of the more complex information that I have printed relate to this particular area. Can I, for the purposes of getting it up and running, ignore the backlighting connections and just do everything else?

If yes to above, how readable will a reverse backlit green/black screen without the backlight?

I take it from the forum discussions that I could bypass the potentiomters and just use a resistor on the +5V line. If this is the case, what size resistor have you found works for a reasonably clear display?

I take it that Pin 1 and 2 provide ground and +5V power for the unit itself and not for the backlighting. Do I simply connect the +5V and ground wires from a molex connector to achieve this with no resistors or any other components?

The diagrams indicate that Pin 15 is LED+ (A) and 16 is LED- (K). But what is the A and K connectors on the opposide end of the LCD PCB (also has "5V" written on it)? Which one is the correct one for supplying power to the LCD backlight? Or do I need to do something with both?

Many thanks....

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[CF Tech]

Backlighting: most of the more complex information that I have printed relate to this particular area. Can I, for the purposes of getting it up and running, ignore the backlighting connections and just do everything else?

Yes. Just leave pins 15 and 15 open (disconnected).

If yes to above, how readable will a reverse backlit green/black screen without the backlight?

It will not be very readable. You will need a bright light shining on it, and it will be difficult to set the contrast correctly without the backlight.

I take it from the forum discussions that I could bypass the potentiometers and just use a resistor on the +5V line. If this is the case, what size resistor have you found works for a reasonably clear display?

Yes. For the CFAH2002A-YMC-JP on a 5v supply, the data sheet recommends 210mA and states that the forward voltage will be approximately 4.2v, so R = (5-4.2)/0.210 = 3.8 ohms, so a 3.9 ohm or 4.7 ohm 1/2 watt resistor will work fine.

I take it that Pin 1 and 2 provide ground and +5V power for the unit itself and not for the backlighting. Do I simply connect the +5V and ground wires from a molex connector to achieve this with no resistors or any other components?

Yes, that should be OK. Be careful not to 1)reverse polarity, 2) use the 12v, 3) short any thing out. The equipment you save may be your own.

The diagrams indicate that Pin 15 is LED+ (A) and 16 is LED- (K). But what are the A and K connectors on the opposite end of the LCD PCB (also has "5V" written on it)? Which one is the correct one for supplying power to the LCD backlight? Or do I need to do something with both?

Use pins 15 and 16, and put the 3.9 ohm resistor in series. Connect like this (+5v)wire(one end of the resistor)resistor(other end of the resistor)(pin 15)LCD(pin 16)wire(ground).

Many thanks....

No trouble.

 

[muzza]

Re: Re: Baby's First LCD

Yes. Just leave pins 15 and 15 open (disconnected).

I take it you mean 15 and 16?

It will not be very readable. You will need a bright light shining on it, and it will be difficult to set the contrast correctly without the backlight.

Excuse the ignorance, but how do you set the contrast once the backlit is up? I make the following assumptions from the diagrams:

a) Pins 1 and 2 are connected directly to ground and +5V respectively.

b) Pin 15 is connected to +5V via a 100ohm pot, plus a resistor in series (say a 3.9ohm 1/2 watt) to make sure I do not kill the backlight by turning the pot to 0. Conversely, Pin 16 is grounded. This controls the backlight.

c) Pin 3 is connected to +5V via a 10k pot, and it controls the contrast. I take it that this uses the ground from Pin 1 or Pin 16?

Use pins 15 and 16, and put the 3.9 ohm resistor in series. Connect like this (+5v)wire(one end of the resistor)resistor(other end of the resistor)(pin 15)LCD(pin 16)wire(ground).

Excellent. So what are the (A) and (K) connectors on the other end for? Do I ignore them completely?

 

[CF Tech]

To adjust the contrast, just tweak the 10K pot until the display is the most visible.

A & K are unused in this situation.

 

[muzza]

Almost home....

I am pretty sure that I have it all worked out, but for the contrast....

+5V goes in to pin 3 on the LCD via the 10k pot which then controls backlight... but where is ground? Does it come back out of pin 1?

Are there no problems with using the 10k pot without a resistor (like you suggest with the brightness)? I take it there will be no problems with setting the pot to 0?

Thanks very much for your help...