LCDInfo.com

I recently purchased a custom CFAG from CrystalFontz, with the T6963 controller. I have run into one problem, and I'm not sure what the root of the problem may be.

We initialize all of our home addresses, modes, etc, but we still don't see anything on the screen, even if we write something to it.

We think it may be one of two things, or both:

#1)
We purchased this LCD no potentiometer on it, so we had Vee and Vo sitting as open. We figured we'd need these for contrast adjusement, so we purchased a 10k pot, hooked the wiper into Vo, and hooked the other two pins on the pot between Vee and 5V (Vee is called '-20 V, Negative Voltage, and Vo is called 'Power Supply For LCD Driver', with no value given). Is it possible that the contrast is still too dim and we're just not seeing the data?

#2)
The microcontroller we're using operates at 40Mhz. We're sure we've accounted for the delays with rise and fall time of certain bits (C/D, RD, etc), but we're still stuck.

Any suggestions anyone?

Thanks,
Shawn

Ok, I figured it out.... it's not exactly good news. Turns out the model has no negative voltage out... essentially, Vee is 0. Can anyone recommend a regulator, or circuit that may do the trick for me?

Thanks!

MAX 870, 871, MAX 1044, ICL 7660

http://www.maxim-ic.com/appnotes.cfm/ap ... umber/1875
Free samples available but they are 0.050" spaced pins for surface mount.
Look for some old MAX870, 871 in an electronics place.

Or
http://pdfserv.maxim-ic.com/en/ds/ICL7660-MAX1044.pdf and get DIP versions free and cascade as in the pdf.

It looks like a simple solution. You could search 555 circuits as well.
For development I am using 3 - 9V batteries with the positive connected to ground and a 50k pot. I just ordered some Crystalfontz CFAG12864 with a negative voltage generator specified.

Hi rfhaley,

thanks for the help! In the end, we've deicded to go for the PT5025 regulator, as space is a major concern for us. The PT5025 can take an input of 5V, and spit out -15V. I checked the contrast at -15V, and it's perfect for what we need.

In case you're interested, this is going to be used in a racecar. We're implementing a gear shifting system that is controlled by the MPC555, with the LCD acting as the driver feedback indicating which gear the vehicle is in. Also, the LCD is going to display stats about water temperature, oil pressure, etc. which are collected via CANBUS.

Sounds interesting

I'm always interested to hear the applications where these are used. If it's possible for you to post some photos of the system later when it's running I'm sure many would be interested to see it.

Hi Henri,

The system is up and going now!! Working just as we have expected it to, and it looks really nice. We're presenting it to the school tomorrow; I'll take some pictures of the whole setup, and post them as soon as I can!

Shawn