The LCD works fine except for sometimes when I apply power (ie turn on the device) the screen goes black. I am sure its some power spike problem. I have an APp1117 5v regulator on the board with a 0.1uf and 10uf on the incoming and 5v lines. Any ideas?

 

Hi,

In order to help you, I need to know what the LCD is part of, a TV SET? A computer board, or a calculator? Also, how is the unit powered (batteries, AC line, etc.)?
It's very unlikely it's a cap on a 5V regulator. But that is easily checked with a DMM or a scope if you have one.

Feel free to contact me with additional questions. I'm a 30+ year degreed electrical engineer.

Good Luck,
Kamran Kazem,
kkazem

 

Part number is NHD-0420D3Z-FL-GBW. Here is a link http://www.newhavendisplay.com/inde...ducts_id=922&zenid=25qd5e5a6575meuv4n9ducfgn3

Its getting power from a 16v battery. It is on a PCB board. Here is a picture of the project, http://dragtraction.com/Octo.JPG

Thank you
Toby

Hi,

In order to help you, I need to know what the LCD is part of, a TV SET? A computer board, or a calculator? Also, how is the unit powered (batteries, AC line, etc.)?
It's very unlikely it's a cap on a 5V regulator. But that is easily checked with a DMM or a scope if you have one.

Feel free to contact me with additional questions. I'm a 30+ year degreed electrical engineer.

Good Luck,
Kamran Kazem,
kkazem

 

How do you know it's not a firmware issue?

 

Because the device works correctly. Its not just one LCD either. I have fourty of them in my office right now and it will do it to any of them. It only does it on startup. This part goes on a race car with a 16v battery. There is a master disconnect switch on the car for battery power. This deal gets its power directly from the switch. When this switch is turned on, everything else in the car is powered too. The screen blacks out every time the switch is closed. Yet if I leave the switch closed and just remove then reattach the ground for this deal the LCD works fine. It has to be a power deal its looking like to me.

How do you know it's not a firmware issue?

 

How long does the screen go black?

 

In my experience, the LCD displays I have used are designed to start up with the block character until data is sent to the display.

 

The LCD works fine except for sometimes when I apply power (ie turn on the device) the screen goes black. I am sure its some power spike problem. I have an APp1117 5v regulator on the board with a 0.1uf and 10uf on the incoming and 5v lines. Any ideas?

try to change ur lcd,if there is the same problem i think you should use PWM to run it

 

There is probably a big glitch on the main rail caused when the motor controller is powered up. Put a big cap on the + pwr input to the LCD unit, like 220uF. Then put a series resistor from the 16v main rail to the + pwr input, choose a resistor that drops a few volts when the LCD is fully powered and operating. I would start with 10 ohms, you may need to go larger after you test it.

That decouples the LCD micrcontroller from the nasty 16v rail, it should solve your latchup problem.

 

Thanks for the input guys. I will give the suggestions a try and report back the results.

When the screen 'blacks' out, it lasts until I repower. Its done it on every one of the LCDs I have tried to far.

Thanks again