No current through circuit, but LED is still on

[gigoiy]

Hello all! I'm building a circuit with that senses current and voltage, using an LED as a load for now. Right now, there is voltage in the circuit and the LED is on, but my multimeter (not current sensor) isn't reading any current despite the LED turning on when I connect the leads of the multimeter. For the life of me, I can't figure out why there isn't any current in this circuit. I am using a voltage divider as a voltage sensor, as well as a N-channel mosfet to open and close the circuit path for unrelated reasons. While debugging, I made sure the mosfet was set high for current flow while reading current with a multimeter.

Here's a wiring diagram:

And here's my code:

int regulator = 2;
int iSensor = A1;
int vSensor = A0;

void setup() {
  pinMode(regulator, OUTPUT);
  pinMode(iSensor, INPUT);
  pinMode(vSensor, INPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(regulator, HIGH);
  Serial.print("Current: ");
  Serial.println(getCurrent());
  Serial.print("Voltage: ");
  Serial.println(getVoltage());
  delay(250);
  //getVoltage();
  //digitalWrite(regulator, HIGH);
  //Serial.println(analogRead(iSensor));
  //delay(250);
}

float getVoltage(){
  float voltageInitial = analogRead(vSensor)/204.6;
  float voltageFinal = voltageInitial/0.166;
  //Serial.println(analogRead(vSensor));
  return voltageFinal;
}

float getCurrent(){
  float finalCurrent = 0.0, adc = 0.0;
  int zeroValue, iValue;
  digitalWrite(regulator, LOW);
  zeroValue = analogRead(iSensor);
  digitalWrite(regulator, HIGH);
  iValue = analogRead(iSensor);
  iValue = zeroValue - iValue;
  adc = adc + iValue;
  adc = adc/100;
  finalCurrent = adc * 0.0732;
  return finalCurrent;
}

[gilshultz]

Your frizzy picture is not much help. The LED will start to glow with a very little current well under 1mA. What is the lowest current range of your meter and what is the burden resistance. I would also take a SWAG and say your MOSFET is not connected properly.

[gigoiy]

Lowest current rating on my meter is 200 micro amps. The burden resistance is 330 ohms. The mosfet goes gate(1), drain(2), source(3) and I believe its connected properly if I'm using it as a switch. My multimeter is reading absolutely zero current though.

[DVDdoug]

I'm also not sure your multimeter is connected correctly... You have to completely "break" the circuit (so no current can possibly flow) and then connect the ammeter in series.

[gigoiy]

I'm pretty sure I break the circuit when I'm reading with my multimeter... The LED turns off when I break the path inbetween the 330 resistor and the LED. Turns back on when I connect the multimeter

[gilshultz]

Schematics are so much easier to read then fuzzy pictures. I will take a SWAG at this, Try shorting the drain to source you should get about 0.6mA. Posting part numbers with links helps, what is the MOSFET part number and what is its Vgs for turn on for 1 amp?

[gigoiy]

The MOSFET is an IRL7833, the current sensors are the acs712-30A, for the voltage divider I'm using a 10k and a 2k resistor and sensing the voltage drop after the 330 ohm resistor and sending it to my arduino. I'll have schematics posted momentarily.

[gigoiy]

I am measuring in-between the LED and the 330 ohm resistor with the circuit broken. I also break the voltage divider off from the led and resistor and isolate it

[gigoiy]

And its not like nothing works in the circuit, cuz everything works perfectly except for when I try to measure current, I'm not getting any readings. And I'm pretty damn sure I know how to measure current so I'm mind boggled

[gilshultz]

Great start with the schematic. I would add the Power and Ground source(s). Try placing a 330 ohm resistor in series with your meter and power supply and measure the current. With Ohm's law you can calculate what you should read. If you get nothing your meter is not working properly. It may have a blown fuse. For your initial testing you do not need the divider, your max voltage is 5VDC the same as the Arduino.

[sterretje]

@gigoiy, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advise on) your project See About the Installation & Troubleshooting category.

[gigoiy]

That is true that I don't need the divider for the initial testing but this is a school project and requires a working voltage sensor capable of sensing up to 25V. But thank you for the reply I will test my multimeter!

[gigoiy]

I do indeed have a blown meter! Thank you!