20x4 lcd display noise protection

[electronicsbuddy]

hello,

i;m using 20x4 lcd display for my project which is for switching igbts with high voltage die to this sometimes display goes blank in running condition we cannot see anything on display and we've to reset the whole system pls. suggest any changes req. thanks in advance.

 

[cobra1]

Have you determined the reason for the blackout?? is it a drop in voltage to the lcd or maybe a drop in voltage to the PIC.

is the pic and lcd fitted with decoupling capacitors??

 

[Boncuk]

LCDs don't like high voltage in their vicinity.

There was my air handling computer installed in an environmental experience lab. It worked alright until they installed an electrostatic filter (30KV) to catch the smoke particles from diesel exhaust gases.

When the filter was almost clogged up with particles the electrodes would fire sparks causing the display of my computer (20m away from the filter) to malfunction (showing either two lines of 40 characters black rectangles or simply blank the screen).

I partly solved the problem by disconnecting the display when it was not required.

To have the display operative at all times you should use a shielded cable and put the display into an EMP-prove (MU) enclosure.

Boncuk

 

[electronicsbuddy]

Thanks for the comments, I checked the voltage at lcd supply points it’s 5v and data patterns on data lines seems to be noise free but still display went blank. After giving high voltage I’m not writing anything to display unless until some inputs like switch pressing or like that is not done by user and other thing is that I cannot keep it away from the high voltage things or relays. I’m thinking to put glue or ferrite sheet on the display drivers will it works. Can anyone suggest me some noise protection technology.

 

[Blueteeth]

Depends if its conducted noise (via the power lines) or radiated noise (though the air).

I would use an oscilloscope on the power lines to see any spikes - but this isn't always available. And of course, the display itself might be just fine, but the microcontroller you're using to drive it might be reseting. It doesn't take much to reset a microcontroller, do you have a cap from the reset line to ground? (if the reset line is active low). Also radiated noise could do the above.

Is this a DIY thing, one you can easily modify, or a ready-made device?

One little trick I do for debugging 'reset issues' is add a tiny bit of code at the start of a microcontrollers program (right after reset/port configuration) which lights an LED, and just loops until I press a button. If it resets when its not supposed to, it'll give a nice clear indication, and only continue about its business when you press a button.

Never heard of ferrite sheet, but I think that fact alone is more than enough reason to get some