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Arduino Forum 16*2 LCD getting weird characters
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  • lcd
  • arduino
Related

16*2 LCD getting weird characters

jrcs
jrcs over 9 years ago

Hi all.

 

This is my first post so I hope it is at the right place.

 

I'm working on a project whose objective is to control two ac loads (one ac fan, controlled by phase angle control and one ac motor controlled by a 5V relay) and output to an LCD the room temperature and the % of fan speed.

 

 

The code I wrote seem to work fine without the AC loads connected. I tested it for long periods of time (+12 hours) and everything is ok.

 

The problem is when I connect both (or just one) AC loads, I always end up with my LCD info corrupted like this:

 

image

 

https://1drv.ms/i/s!Ah12lhUG5VG8g9FOhR9Y0ccFTsq2Rg

 

Sometimes past 2 minutes, sometimes past 10 minutes... It's random but it always end up like this.

 

 

I'm guessing it's noise problems due to the loads switching TRIAC/Relay. The TRIAC its connected trough a optocoupler but the relay it's directly connected to the arduino.

 

 

First, I put the lcd.clear() function in my code to "rebuild" the info from time to time but it doesen't work 100% and it's not a "clean" solution for the pourpose.

 

 

The AC loads are connected to the grid but the arduino is powered from my computer's usb port. Already put an EMI filter into AC main input of my loads but no solution.

 

Is there a solution to this problem? Any help?

Sorry for my poor english but I'm a little bit rusty.

 

Regards

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Top Replies

  • niko.vicencio
    niko.vicencio over 8 years ago +3
    Hi I had the same problem, the lcd showed random characters when the electromechanical relay commutated. I solved this problem, changing the relay by a ssr (Solid state relay). I hope that my answer help…
  • WarrenW
    WarrenW over 9 years ago +2
    How are you driving the relay from the arduino? Direct off the micro or via a transistor? Does the relay have a snubber cap across the coil and a back emf diode? Does the arduino have a filter capacitor…
  • Robert Peter Oakes
    Robert Peter Oakes over 9 years ago +2
    Can you please provide a schematic of your setup and also a full picture (Cant see all your connections in the one provided. You can upload them right into this community post. I have done what your describing…
  • vicky62
    vicky62 over 5 years ago

    Yes I’m also facing the same issue. Is there a solution

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  • phoenixcomm
    phoenixcomm over 5 years ago

    Try and use a separate power supply for both the ssr and the Arduino!

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  • digitallelectronic
    digitallelectronic over 5 years ago

    I have found a way to solve this issue as the AVR isnt hanging thats sure & only LCD controller is getting noise.

     

    1st ) use internal clock oscillator to prevent AVR from hanging

     

    2nd) Reinitialize the LCD after every time you turn on & off the Relay or contactor or any inductive load

    (lcd.begin(16, 2);)

     

    This way my problem got solved

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  • phoenixcomm
    phoenixcomm over 5 years ago in reply to digitallelectronic

    gordonmx "2nd) Reinitialize the LCD after every time you turn on & off the Relay or contactor or any inductive load

    (lcd.begin(16, 2);)"

    nope!!

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