CFAG320240C-FMI-T Wiring

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Corg8d

New member
Before we begin let me first state that I understand that Crystalfontz does not offically support this LCD and the I do not hold Crystalfontz liable for any technical help given if such help results in me making my LCD implode and/or taking my PC with it. ;)

First, here is a schematic of how I have the CFAG320240 currently wired. It does work with this configuration, but is extremely unstable.



My questions are:

1. I picked up wiring the contrast to +5v as opposed to the ground from another thread. Is this OK or should I change it to ground?

2. I also picked up the +5v for the reset (the tech didn't make a comment on the schematic) from the same thread. Is this too much (i.e. should I add a 10K resistor) or is the +5v OK? Or should I go with the typical reset button with the 10K resistor and 100nF Cap?

3. Lastly, in looking at the schematic does it look like all the connections are correct?

Any help you could provide would be greatly appreciated.

Thanks,

Corg8d
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C

Corg8d

New member
Ok, since installing it into the case it has a new problem. Funning thing is that nothing has changed in the harness used. Upon firing it up the center of the LCD was white in the shape of a circle. After the LCD ran for a 10 inutes or so the center gradually returned to normal, but the LCD is again unstable. Also, when I start the LCD (Liquid MP3) the LCD begins fairly dark, and then returns to normal after a couple of minutes. Unfortuately, shortly after it returns to normal the LCD goes blank. Stop and start the software and we are off and running again.

I understand that this LCD has no official support so I am not suprised at the lack of response from the techs. Thought I would give it a shot though.

Corg8d.
 
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Corg8d

New member
Updated schematic of the wiring as it is currently along with a shot of the wiring harness.





Corg8d
 
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Corg8d

New member
Well, due to the absolute abscense of technical assistance (at least from Crystalfontz), I have decided to go with a with a different vendor. Even after what I know to be correct wiring, the display is still sup-par and very tempermental.

Corg8d
 
CF Tech

CF Tech

Administrator
We do offer full support for our displays when they are used in their intended applications. As you seem to be aware, the CFAG320240C series is not intended to be used in a PC application.

Looking at your photos, you seem to have the skill and much of the understanding that would be needed to get away with connecting this display in a PC environment. At one point you state "it works great now", then you install it into the case and things go south. My guess is that somehow something was damaged as you installed it into the case.

Your schematic shows an off-board contrast control. You must center the built-in contrast control (white knob on the back of the display) if you want to use an external contrast control. If these two controls are "fighting" that could cause trouble. This display is temperature compensated, if too much current is being forced through the thermistor there could be some odd behavior as you are seeing.

The reset line should be low to start and then high for operation. If the display is not properly reset after power-up, that could cause some trouble. You can probably get away with a simple RC, or better yet would be a nice 3-pin reset chip.
 
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Corg8d

New member
I am sorry for the outburst. I was getting very frustrated, it was late, and this forum became the outlet.

I was also thinking that it may have something to do with the contrast.

Tonight I am going to pull the unit back out of the case and begin testing. Speaking of the off-board contrast, I have seen both the grounding and supplying +5v to the wiper. Which is best? Or is it better to just use the onboard contrast control?

Any help is appreciated.

p.s. Regarding the onboard contrast, is it just a matter of putting a 10k resistor between Vo and Vee or is there more to it than that. Or do I just leave them disconnected?

Again, sorry for the rant.

Corg8d
 
CF Tech

CF Tech

Administrator
I would have to hook one up again to check (it has been a while :) ) but I think that you do not need anything external connected to Vee or Vo if you are going to use the on board contrast control.
 
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Corg8d

New member
It was definately something with the contrast (just leave the Vo and Vee disconnected). My contrast is back to normal. It also seems as though I have something weird going on with my grounds. All of the grounds were connected via the PSU. But the second I corrected the contrast the display became partially garbled. No matter what I did it didn't (stop/start the software, reset the display, etc...) it didn't help. So I rerouted the R/W to ground via the parallel port and wahlah, everything was back to normal. The display was still unstable though, blanking out after only a few minutes. So I pulled the Vss and Frame ground and connected them to the parallel ground as well and ran a tap to the connector frame. It went for fifteen minutes before it scrambled. I don't know if this is better than it blanking out or not?

2 steps forward, 1 back.

Corg8d
 
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