voltage across LCD(16x2) is fluctuating when connection HC-06 with arduino UNO

Hello!!
I am trying send IR signal using arduino uno + bluettoth module(HC-06) with android phone.

my wiring are:
Arduino uno LCD(16x2)
VCC → lcd pin no 2
GND → lcd pin no 1,3,5
digital pin 9 → lcd pin no 4
digital pin 8 → lcd pin no 6
digital pin 5 → lcd pin no 11
digital pin 4 → lcd pin no 12
digital pin 6 → lcd pin no 13
digital pin 7 → lcd pin no 14

HC-06 connection with arduino are:

Arduino uno HC-06
VCC → vcc
GND → gnd
TXD → digital pin 10, (rxd pin created with the help of softwareSerial library)
RXD → digital pin 12, (txd pin created with the help of softwareSerial library)

Now, when i powered up the arduino uno, i noticed a voltage fluctuation on lcd screen.
this fluctuation is from 4.5 v to 3.70v (clearly visible on lcd screen), same thing happening with bluetooth also.
But when i broke the hc-05 wiring with arduino uno. there is no fluctuation.

since lcd and bluetooth’s vcc are connected in parallel so both gets the equal vcc (from arduino vcc), then why this fluctuation is happeing???

kindly suggest how do i stop this fluctuation.

I think the HC06 should connect to 3.3v not 5v. Be careful not to damage it.

...R

i got a new JY-MCU bluetooth module but in this also voltage is fluctuation.
JY-MCU operation voltage is 3.6 v to 6v. this info mension on back side of JY - MCU.

ohh…i got info that TXD pin of bluetooth module should be connected with 3.3V level of arduino RXD…
i had conntcted bluetooth txd directely to RXD (digital pin 12) pin of arduino.

does this able to cause the problem…???

i had conntcted bluetooth txd directely to RXD (digital pin 12) pin of arduino.

That should not cause a problem. I use the same module connected that way.

Bijendra, how are you powering the Uno?

this fluctuation is from 4.5 v to 3.70v

What is the voltage on the Uno +5V pin without LCD or BT connected, and with just LCD connected?

hello Hackscribble!!

it is 4.56v

And how are you powering the Uno? From USB or from a different power supply?

4.56V sounds a little low with nothing connected to the Uno.

BijendraSingh:
ohh..i got info that TXD pin of bluetooth module should be connected with 3.3V level of arduino RXD..
i had conntcted bluetooth txd directely to RXD (digital pin 12) pin of arduino.

How is pin 12 RXD? Please post your code and a diagram of how everything is connected - photo of a drawing will be fine. And post a link to the data sheet for your Bluetooth module.

Connecting 3.3v TX to 5v RX should work fine (it does with my HC06) but connecting 5v Tx to 3.3v Rx will probably cause a problem.

...R

sorry for late reply..!

And how are you powering the Uno? From USB or from a different power supply?

i am powering from USB (connected to pc).

Hello Robin2!
sorry for late reply!!

How is pin 12 RXD? Please post your code and a diagram of how everything is connected - photo of a drawing will be fine. And post a link to the data sheet for your Bluetooth module.

i got every info from below link

#include <LiquidCrystal.h>
#include <SoftwareSerial.h>

const int rxPin = 10; //SoftwareSerial RX pin, connect to JY-MCY TX pin
const int txPin = 12; //SoftwareSerial TX pin, connect to JY-MCU RX pin

SoftwareSerial mySerial(rxPin, txPin); 
LiquidCrystal lcd(9,8,5,4,6,7);

int state = 0;        

void setup() {
  lcd.begin(16,2);
  mySerial.begin(9600);
  lcd.print("done!!");
  delay(1000);
}

void loop() {    // here we can see that voltage across lcd is varrying rapidly.
                 // but when connection establishes between android phone with arduino via bluetooth(HC-06) this fluctuation is turned off.
  if(mySerial.available() > 0){   
    state = mySerial.read();
    delay(20);
    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print("RECV: ");
    delay(20);
    lcd.setCursor(10,0);
    lcd.print(state);
    delay(500);   // if delay is provided to see how many data is arriving (for testing only).
  }
}

actully, not only the lcd the voltage across audio sensor is also fluctuating.
i tried to put rc circuit between lcd and ground to smooth the voltage, still result is same… :disappointed_relieved:

You haven't posted a link to the datasheet for the JY MCU module so I can only assume that the Github link has the correct wiring details. You should check for yourself.

If you have a multimeter I suggest you measure the current being drawn by the module. Also use the multimeter to measure the voltage on the 5v pin in order to verify that analogRead() is giving the correct value.

...R

thanx for replyi!!

You haven't posted a link to the datasheet for the JY MCU module so I can only assume that the Github link has the correct wiring details. You should check for yourself.

datasheet link of HC-06,

If you have a multimeter I suggest you measure the current being drawn by the module.
 Also use the multimeter to measure the voltage on the 5v pin in order to verify that
 analogRead() is giving the correct value.

my voltage connection are :
arduino VCC -> lcd vcc , jy-mcu vcc and vcc of audio sensor
arduino gnd -> lcd gnd , jy-mcu gnd and gnd of audio sensor.

using multimeter i measure voltage across jy-mcu vcc and gnd, which is 4.39v to 4.09v (fluctuating)
also voltage across audio sensor is same 4.38v to 4.09v (fluctuating).

i more thing i need to tell you that when i powered up JY-MCU its red led start blinking (which is normal) and voltage fluctuation starts, but after connecting jy-mcu to any android phone using android bluetooth terminal app voltage across jy-mcu is 4.42v (stable) and same across audio sensor , lcd also.

That PDF that you linked to is for a 3.3v product - not a 5v product. So, the question is - have you really got a 3.3v HC06 or have you posted a link to the wrong datasheet? - My strong suspicion is that you have a 3.3v HC06.

And you don't seem to have measured the first thing I asked - the current.

...R

Image of the complete setup. I have tried using the bluetooth JYMCU with the 3.3 volt power supply from the arduino uno, but have still faced the same issue.

Please find attached an image of my setup.

My strong suspicion is that you have a 3.3v HC06.

In attached image you can varify that i have JY-MCU (which contain hc-06).
i followed the github link of jy-mcu bluetooth module thats why i connected vcc of jy-mcu with 5v suppy

And you don't seem to have measured the first thing I asked - the current.

current is also fluctuating from 40.2mA to 1.03mA

I don't doubt that you are using a JY-MCU. But I don't see any evidence that it is a 5v device apart from that Github link which doesn't explicitly address the point.

However if the maximum it draws from the Arduino 5v pin is 40 mA that should not cause any voltage variation.

I guess it's possible the LCD is almost drawing too much current and the little extra taaken by the BT module is the straw that breaks the camel's back.

Can you test the voltages on your system without the LCD connected?

I assume the only problem is that the BT module seems to cause a flicker or dimming of the LCD display?

Are you sure all the connections are good - corrosion on plugs or sockets or poor soldering might have strange effects.

...R

But I don’t see any evidence that it is a 5v device apart from that Github link which doesn’t explicitly address the point.

kindly see the below link, they powered 5v to jy-mcu.

another thing i tried with 3.3v also.

I guess it’s possible the LCD is almost drawing too much current and the little extra taken by the BT module is the straw that breaks the camel’s back.

Current across LCD is pretty strange.
i got .552 mA current and 4.42 V voltage. (when Bt is not connected)
.552 to .509 mA current and 4.42 V to 3.9v voltage. (when Bt is connected)

37.2 to 0.76 mA current and 3.29v to 3.0 voltage Across BT.

I assume the only problem is that the BT module seems to cause a flicker or dimming of the LCD display?

yes!! every thing work fine after disconnecting BT from circuit.

Are you sure all the connections are good - corrosion on plugs or sockets or poor soldering might have strange effects.

connections are good. But not sure about corrosion or sockets.

One more thing i tried to disconnect BT when i am going to capture sound from mic.
to achieve this i am using transistor as a switch. Circuit diagram is available at

http://www.electronics-tutorials.ws/transistor/tran_4.html

#include <LiquidCrystal.h>
#include <SoftwareSerial.h>

const int rxPin = 10; //SoftwareSerial RX pin, connect to JY-MCY TX pin
const int txPin = 12; //SoftwareSerial TX pin, connect to JY-MCU RX pin
                     // level shifting to 3.3 volts may be needed

SoftwareSerial mySerial(rxPin, txPin); 
LiquidCrystal lcd(9,8,5,4,6,7);

//const int ledPin = 13;  // led pin
int value = 0;
int state = 0;        // if state is 1, the LED will turn on and
                      // if state is 0, the LED will turn off
int flag = 0;         // a flag to prevent duplicate messages

void setup() {
    lcd.begin(16,2);
    mySerial.begin(9600);
    Serial.begin(9600);
   pinMode(A4, OUTPUT);
    digitalWrite(A4, HIGH);
    lcd.print("done!!");
    delay(1000);
}

void loop() {
  
     digitalWrite(A4, LOW);    // base pin of transistor is connected at A4,  BT is powered off
      value = analogRead(A0);  
     Serial.println(value, DEC);
     digitalWrite(A4, HIGH);      // BT is powered on

    if(mySerial.available() > 0){
      state = mySerial.read();
      delay(20);
      lcd.clear();
      lcd.setCursor(0,0);
      lcd.print("RECV: ");
      delay(20);
      lcd.setCursor(10,0);
      lcd.print(state);
      mySerial.println("RECV:");
      delay(500);   // if delay is provided to see how many data is arriving.
    }
}

this approach is working fine at some extent but is not reliable…

Current across LCD is pretty strange.
i got .552 mA current and 4.42 V voltage. (when Bt is not connected)
.552 to .509 mA current and 4.42 V to 3.9v voltage. (when Bt is connected)

Please explain exactly how you are making the current and voltage measurements. Where are you connecting in the circuit?

How is the Arduino powered when you make these measurements (USB or external supply).

Also, are you sure that these readings are 0.552mA, not 0.552A?

37.2 to 0.76 mA current and 3.29v to 3.0 voltage Across BT.

Same question - please explain how and where you are taking these measurements.

Hackscribble:
Please explain exactly how you are making the current and voltage measurements. Where are you connecting in the circuit?
etc etc

You got there before me.

yes!! every thing work fine after disconnecting BT from circuit.

That’s not exactly the answer to my question. I had assumed everything was working OK (apart from the flicker) when the BT was connected? Is that true?

…R

Hello Hackscribble!!

How is the Arduino powered when you make these measurements (USB or external supply).

arduino uno is connected to lenovo pc usb port (4.52v across arduino vcc).

Please explain exactly how you are making the current and voltage measurements. Where are you connecting in the circuit?

red male wire of multimeter is connected to VmAohm labeled female socket.
black male wire of multimeter is connected to COM labeled female socket.

Current measurement across LCD:
multimeter nob is pointing to 200mA under A(–) digital section.
vcc of arduino → MM(multimeter) red wire
MM black wire → vcc of LCD.
gnd of arduino → gnd of lcd

got 1.05mA current :frowning:

Voltage Measurement across LCD:
multimeter nob is pointing to 20V under V(–) ie digital section.
vcc of arduino → Vcc of LCD
gnd of arduino → gnd of lcd
MM Red wire → vcc of LCD.
MM black wire → gnd of LCD.

got voltage 4.42V (flicker)

Current measurement across BT:
multimeter nob is pointing to 200mA under A(–) digital section.
vcc of arduino → MM(multimeter) red wire
MM black wire → vcc of BT.
gnd of arduino → gnd of BT

got 39.9mA current

Voltage Measurement across BT:
multimeter nob is pointing to 20V under V(–) ie digital section.
vcc of arduino → Vcc of BT
gnd of arduino → gnd of BT
MM Red wire → vcc of BT.
MM black wire → gnd of BT.

got voltage 4.48V (flicker)