Current reading through multimeter

Hi guys,

So basically i’m trying to read the current in my device setup connection, and as such, i have use a digital multi-meter, turn the knob to 10A with red probe to the 10A port of the multimeter and black probe to the com port of the multimeter, and lastly, i have place both red and black probes in series with my device setup. Images of rough drawn schematic as well as image of my setup is attached as shown.

With that said, the readings from the multimeter has shown an approximate value of 0.04, which i guess is 0.04 A? so the question is why is the readings wrong? As seen from the attached image,my pololu step down regulator 5V 2.5A is attached to the device setup. So why isnt the value in the Multimeter show a value of 2.5A? Could it be due to the fuse blown? if not what is the reason?

Side note:

→ carbon dioxide sensor, https://www.dfrobot.com/product-1549.html
→ adafruit ultimate gps sensor, Adafruit Ultimate GPS Breakout - 66 channel w/10 Hz updates [Version 3] : ID 746 : $39.95 : Adafruit Industries, Unique & fun DIY electronics and kits
→ TCS3200 Color Sensor, http://digitalmeans.co.uk/shop/colour_sensor-tcs3200
→ temperature sensor, https://www.banggood.com/DS18B20-DC-5V-Digital-Temperature-Sensor-Module-For-Arduino-p-930691.html
→ coin vibration motor, https://www.aliexpress.com/item/Brand-NEW-1PCS-DC-3V-60mA-9000-2000RPM-Phone-Coin-Flat-Vibrating-Micro-Vibration-Motor-Accessories/32800295518.html?spm=2114.search0305.4.1.3blfUe
→ RGB LED
→ Pololu step down 5V 2.5A, 5V, 2.5A Step-Down Voltage Regulator D24V22F5
→ Lipo battery 7.4v 850 mAh
→ arduino nano

inky90:
which i guess is 0.04 A?

Yes, the unit displayed is always the same as the range selected.

inky90:
So why isnt the value in the Multimeter show a value of 2.5A?

Because apparently you don't understand how a voltage source works :wink: The step down module steps the voltage down to 5V. That's the only thing that's regulated. The current is just determined by what you connect. If you connect nothing it still outputs 5V but 0A. The 2,5A is just the MAX the module can supply to whatever you connect. So apparently whatever you have connected draws 0,04A :slight_smile:

So what u meant was that all my sensors combined together only draws 0.04A?

Then this brings me to another question, so previously before buying the step down regulator, i was facing current issue, this is said because i had directly pluck my arduino nano 5v pin to supply voltage to all my sensors, but then some of my sensors are not able to work (such as carbon dioxide not able to power up, colour sensor led lights flickering). and as such the step down regulator was implemented to address the current draw issue.

so then the question is if u mentioned that my current draw is only 0.04A, then why arduino nano is not able to support this? it should be able to supply more than 0.04A right i suppose ?

sorry still kinda new to these stuff

The Arduino is indeed not capable of supplying any significant amount of current, espesially if the input voltage is high. Although 40mA seems a bit low because of the GPS (or is it not initialized?). The rest of the sensors seem low power to me. But you do measure on the 10A range of random brand DMM. Try it on the 200mA range.

And I did not read through all the sensors and components. But you also didn't supply a full schematic :wink: For example the motor and the led, how are they powered?

Remember that a multimeter only shows the average current or voltage on a time-scale of a second or so.
Your circuit may be pulling 2A pulses for 2% of the time, or a steady 40mA all the time, the multimeter
cannot distinguish the two, but your sensors and processor will care if the supply drops for even a few
microseconds due to high current pulses overwhelming the supply...

A classic example of this is a GSM module, which can take 2A or more during tranmission, but
transmit in time-slices 1/8th of the time, so a multimeter would show about 0.3A, but a 1.5A supply
would be completely inadequate to power it.

septillion:
The Arduino is indeed not capable of supplying any significant amount of current, espesially if the input voltage is high. Although 40mA seems a bit low because of the GPS (or is it not initialized?). The rest of the sensors seem low power to me. But you do measure on the 10A range of random brand DMM. Try it on the 200mA range.

And I did not read through all the sensors and components. But you also didn’t supply a full schematic :wink: For example the motor and the led, how are they powered?

Hi, i have tried putting the digital multimeter on the 200mA and port remains unchange (red probe on 10A and black probe on com). the readings is at 00.3 to 00.4. So i assume that this is the same reading as before. ~~ Addition note: the value jumps from 00.3 to 1.0 everytime my vibration motor and LED vibrate and light up

all sensor and other components are powered by the lipo battery 7.4v 850 mah in which it is step down by pololu regulator of 2.5A 5V. which then the output (Vout) from pololu is connected to the main red and blue tracks of the breadboard, and thus supplying power to all sensors as well as motor and LED

the motor is connected via the website provided: Tutorials | Tinkbox

The RGB LED is connected via this: How to use a RGB LED with Arduino | Tutorial

image attached include a schematic that i drawn on my own. do apologise if its not drawn as what its suppose to be like. newbie here.

MarkT:
Remember that a multimeter only shows the average current or voltage on a time-scale of a second or so.
Your circuit may be pulling 2A pulses for 2% of the time, or a steady 40mA all the time, the multimeter
cannot distinguish the two, but your sensors and processor will care if the supply drops for even a few
microseconds due to high current pulses overwhelming the supply...

A classic example of this is a GSM module, which can take 2A or more during tranmission, but
transmit in time-slices 1/8th of the time, so a multimeter would show about 0.3A, but a 1.5A supply
would be completely inadequate to power it.

Hi mark, may i assume that u are referring to arduino nano do not have sufficient current to supply all my sensors?

inky90:
So i assume that this is the same reading as before.

Sorry, no cake for you :wink: If you want to use the mA range then you have to put the plug in the VΩmA as the meter clearly suggests :wink: After that, you should get a reading in mA :slight_smile:

inky90:
the motor is connected via the website provided: Tutorials | Tinkbox

So it's still connected to the Arduino 5V? Then you're still loading the Arduino regulator with it :wink:

inky90:
The RGB LED is connected via this: How to use a RGB LED with Arduino | Tutorial

So the Arduino pins provide the power for the LED. Aka, again, the Arduino regulator provides the power.

And what Mark says is that the GPS uses power in short but high bursts. But the average power isn't that high. So 40mA might be right for an average value (or at least what a cheap meter makes of it) :slight_smile: But although short, the Arduino regulator can't supply 2A even for that little while and thus gave you problems.