LCD influenced by current Sensor

I have arduino project that read AC current using ACCS712-20A sensor. I know that LCD display will show the weird characters if induced by AC current. But in this case, I just read the current from current sensor. No Direct connect from AC wire to the board (except in ACS712 sensor). The sensor uses A0 pin to read the current. So, how to fix that?

I assume you mean the sensor is an ACS712. It would be helpful if you provided a schematic. In particular, address the grounding of the devices.

In this order, I'd find the answers to these questions: Have you tested your LCD/Arduino separately from the current sensor? Have you tested the LCD/Arduino connected to the current sensor but with the sensor disconnected from the AC current source? Make sure that you're not sending carriage returns/line feeds to the LCD. This is commonly done by incorrectly using println() to the LCD instead of print(). This can be a little hard to find because it doesn't look like an error in the serial monitor. For these conditions, have you used the serial monitor to verify the LCD and the serial monitor provide the same information?

If everything above operates as you expect, compare the LCD display to the serial monitor output while supplying the AC current.

arloG: I assume you mean the sensor is an ACS712. It would be helpful if you provided a schematic. In particular, address the grounding of the devices.

Yes, I mean ACS712. Sorry for typo.

arloG: In this order, I'd find the answers to these questions: Have you tested your LCD/Arduino separately from the current sensor?

Yes, and it works fine.

arloG: Have you tested the LCD/Arduino connected to the current sensor but with the sensor disconnected from the AC current source? Make sure that you're not sending carriage returns/line feeds to the LCD. This is commonly done by incorrectly using println() to the LCD instead of print(). This can be a little hard to find because it doesn't look like an error in the serial monitor.

Yes, and it is works fine too.

arloG: For these conditions, have you used the serial monitor to verify the LCD and the serial monitor provide the same information?

Yes, because I send the current measurement result to serial monitor too. And it works fine (same information).

arloG: If everything above operates as you expect, compare the LCD display to the serial monitor output while supplying the AC current.

The only problem is if I connect the AC load, The LCD display become unreadable (unknown character).From serial monitor I can read that the current is increased. But, I can't compare the display, because the LCD not readable anymore.

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From this case, I think it is because grounding problem? because even I disconnect Analog Pin from current sensor when AC source is connected it will disturb the LCD display. So, how to fix this problem?

The only problem is if I connect the AC load, The LCD display become unreadable (unknown character).From serial monitor I can read that the current is increased. But, I can't compare the display, because the LCD not readable anymore.

Does the serial monitor value match what you expect? Does the LCD sometimes match the serial monitor value?

At first look, your problem sounds like the high current part of the circuit is causing electro-magnetic interference with the Arduino/LCD. Your answers make me doubt this. If you get valid readings on the serial monitor, it seems like the problem likely is not emi - at least not emi with the arduino and with the current sensor.

There's a couple of more things to look at on the hardware side.

  1. The application data here ACS712 current sensor shows a couple of capacitors that aren't in your schematic. These are probably necessary. They are shown on the SparkFun page, too. Sparkfun 0712.pdf

The capacitor from FLT (filter) to ground is intended for noise management. So this is a prime candidate.

  1. What is the source of the 5 volts supplied to the sensor? As noted in 1. above, make sure this voltage is filtered. The sensor uses very little current. To simplify things while debugging I'd use the Arduino +5 to power the sensor. Your drawing does show the Arduino ground properly connected to the sensor and to the LCD.

If these two changes don't make it better, post your code.

arloG: 1. The application data here ACS712 current sensor shows a couple of capacitors that aren't in your schematic. These are probably necessary. They are shown on the SparkFun page, too. Sparkfun 0712.pdf

The capacitor from FLT (filter) to ground is intended for noise management. So this is a prime candidate.

OK, I'll try this. But for temporary I use re-initialize the LCD use LCD.begin everytime the conductor is connected to AC source. And it is works fine.

arloG: 2. What is the source of the 5 volts supplied to the sensor? As noted in 1. above, make sure this voltage is filtered. The sensor uses very little current. To simplify things while debugging I'd use the Arduino +5 to power the sensor. Your drawing does show the Arduino ground properly connected to the sensor and to the LCD.

If these two changes don't make it better, post your code.

I use separate power supply. But when I try use arduino 5 volts supply. It works the same way.