I am using arduino mega with LCD 4X20 character to measure weight by 40 kg load cell and pt 100 to measure the temp. I have 4 output to 4 relay module. all are powered from 12vdc /3 amp Power supply..
the problem is.. the display started normally showing every thing perfectly.. but when the output comes out and the loads runs.. random characters appear
is the power supply is not enough? or another problem..
Please advice. 
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4Please show you circuit and your code – chrisl Sep 29 '19 at 15:23
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1start with a simple sketch that displays 0123456789abcdefghij on every line ... then wiggle wires – jsotola Sep 29 '19 at 17:02
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1Do you know what character generator ROM is built into that HD44780 4X20 display? What signals have you wired from your Arduino? Have you tied the R/W line to GND? – Dougie Sep 29 '19 at 17:07
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1Please read How to ask a good question for Arduino Stack Exchange – sa_leinad Sep 30 '19 at 12:48
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@Ashraf Nassar There could be a number of reasons for this, from connection issues to bad libraries – Coder9390 May 14 '21 at 11:33
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Does this answer your question? Why does my LCD display random characters? – Coder9390 May 14 '21 at 11:40
2 Answers
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Random Characters can Happen in several ways.
- Check the Wires for: Loosen Ends; Broken Wires and Wrong Pin Connections.
- Check your Code.
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I'd suspect that it is a software error. Did you check your circuit if it induces desync between the Arduino and the LCD, or did you just use the wrong drivers?
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