WCS 1800 (Hall effect sensor) Doesn't detect current

[lakindumuhandirumge]

I am trying to use the WCS1800 to detect the current passing through a wire. However, the adc value remains at 0.

The Aout pin is connected to GPIO pin 35 of T-Beam .

The wire passing through the sensor supplies 5V, 2A power the RS485 relay. The current direction is also correct yet the adc reading remains 0. Below is the code I use.

int currentpin = 35;

void setup() {
Serial.begin(115200);
pinMode(currentpin, INPUT);
}

void loop() {
int adc = analogRead(currentpin);
Serial.print("ADC value is: ");
Serial.println(adc);
float adc_voltage = adc * (5 / 4096.0);
Serial.print("ADC voltage value is: ");
Serial.println(adc_voltage);
delay(10000);
}

And for anyone concerned why I am directly connecting the Aout pin to the T-Beam insteading of using a voltage divider to step it down to handle 3.3V, the T-Beam can take upto 5V without an issue. I confirmed it with the manufacturer.

Thanks for any help!

Thanks.

[Railroader]

Please make and post schematics.

[kmin]

@lakindumuhandirumge

The wire passing through the sensor supplies 5V, 2A power the RS485 relay.

And how much is that relay drawing current? 100mA?

[lakindumuhandirumge]

Hello, I drew the schematic.

[lakindumuhandirumge]

It draws 400mA. The sensor is the 35A one, do you think it is too small for the sensor to detect?

[kmin]

It's lowish. For testing I would try something higher.
Also do you pass only one wire through the sensor? Not + and - together.

[lakindumuhandirumge]

Also do you pass only one wire through the sensor? Not + and - together.

I just pass the wire to the relay from the power supply (adapter). Am I supposed to pass the wire twice to create a difference?

[kmin]

"wire" means +5V or +5v and gnd together? Aka cable.

[lakindumuhandirumge]

Yes the +5v and ground cable

[kmin]

they are canceling each other. +400ma-400ma= 0mA
You need to pass only +5V without gnd.

[Railroader]

There must be a signal GND to the F-beam.

[lakindumuhandirumge]

Do I connect the ground from the sensor to the T-Beam instead of the ESP-32?

[lakindumuhandirumge]

I tried it but the reading seems to be at 0 still

[davidefa]

As already said:

• all gnd have to be connected together
• only 1 wire have to pass inside the transformer ( not the cable with 2 wires )
• the esp32 is not 5V tolerant ( inside the t-beam there is an esp32 )
• your sensor works even with 3.3V so power it with 3.3V
• the sensibility is 72mV/A so at 0.4A your reading is 28.8mV ( +vcc/2 as the output of the sensor is centered at vcc/2 )

P.S.
Is the t-beam a lylygo t-beam ( so why powering the sensor from a different esp32 and not directly from the t-beam )?

[kmin]

Did you read post#11? Without gnd you don't get that sensor output voltage on gpio35

And what's the role of that other Esp32 on your setup??

[Railroader]

To the GND of the A0 input circuit.

[SurferTim]

Hall effect sensors detect magnetic fields, not current. Make the field stronger by wrapping the power supply wire around a small iron core.

[lakindumuhandirumge]

Thank you for the reply. I changed the circuit as you mentioned. However, I still face an issue.

This time I have connected the sensor's Vcc, gnd and Aout pins to T-Beam only. ESP32 is being used to power up the RS-485 relay.

I can now get a reading on the GPIO of T-beam. However, this value which is around 2800 (adc value) doesn't change when I power up the esp32 (the relay). It seems to be constantly around that region.

Thanks

[TomGeorge]

Hi, @lakindumuhandirumge
Ops sensor

Wind the wire through the sensor loop three or four times, that will give you a bigger output for a given current.

Do you have a DMM? (Digital MultiMeter)

Measure the DC volts on the sensor output with respect to gnd.

Can you post some images of your project?
So we can see your component layout.

Tom...

[davidefa]

The output of the sensor is ratiometric and centered around vcc/2 ( ie 2048 raw ad ) so 2800 is a little bit too much.
The fact that the reading is not changing too much is 'normal' considering the sensitivity of the sensor around 53mv/A ( when powered at 3.3V ) which is very low for your use, to increase sensitivity wind the wire in more loops ( 10 loops = 0.5V/A which is still not a great sensitivity if you are sensing 400mA )
Did you mount the sensor correctly ( the arrow should point the vdd pin )?
Also what is a rs485 relay?
Are you sure esp32 is capable of supplying 400mA to this rs485 relay ( did you measure it )?