How to get measurements such as Volt, Ampere, mWatt on Arduino

Projects Programming
1

Hello, I need to measure a device that consumes up to 3-4 Amperes current, 5 Volt and the relevant Power in mWatts. Any reliable sensor for this that can be connected to Arduino MEGA 2560 and realize those measurements. The problem is that a INA219 module that I used in the past, and the cables I used minimize the Voltage and the device collapses, because it need to bypass the sensor on the power supply cables. And also I cannot use thick cables on a breadboard. Any ideas???

2

You could use an ACS712 current sensor. The voltage is known, you can just calculate the power.

3

For voltage?? It is never stable in practice...

4

The device ?

5

A custom GPU accelerator. Too much energy consumer...

6

In case I cannot use thick cables that can handle 3-4 Amps. Can I use two INA219, so instead of using one thick cable, to use 2 thinner and sum the current from these two INA219?

7

alex5678:
For voltage?? It is never stable in practice...

Then measure it too. That part is very easy. Did you find some problem with using the ACS712 to measure current? It uses Hall sensing so the voltage drop is minimal. The INA219 modules I see online have a 0.1 ohm current sense resistor, so you will have a significant voltage drop at the load end.

8

Remove the shunt resistor from the board. Use an external shunt.

Then you can connect whatever thickness wires you want to it.

9

pcbbc:
Remove the shunt resistor from the board. Use an external shunt.

Then you can connect whatever thickness wires you want to it.

And what about the other cables of the INA219? Like Vcc, GND?

10

alex5678:
And what about the other cables of the INA219? Like Vcc, GND?

No difference at all.

11

aarg:
No difference at all.

What do you mean? Should I use thick cables or not?

12

How many Amps can a breadboard handle in each cable? Maximum?
I am thinking of using 1.5 Amps on each cable. Do this kind of cables exist?

13

[u]Wire Gauge & Current Chart[/u].

I'm not sure about breadboards but more than 1A is probably "pushing it".

14

@alex5678, you're on the wrong track. With an external current shunt, none of the wiring except the wires connected directly to the shunt will carry any significant currents. This is obvious from the circuit, if you sketch it. As mentioned above, you have to remove the on board shunt resistor, if there is no facility for bypassing it.

15

I want to ask something similar, but if you find it irrelevant to the topic, I can open a new one. In case I don't want to use INA219,, I thought of using 2 parallel USB power gauges (that are more flexible) . so each one can handle up to 2 Amps, so 4 Amps in total. I will use Arduino MEGA 2560, which contains 4 UART, so each UART (2 in total) will receive data from each power gauge and add the current, the Voltage will be the same (nothing to add here) and the Power consumption which will be variable, and it does not matter since I can write code to the Arduino to calculate a new power as a result of the summed current multiplied with the Voltage. Can this work?

psprsllel_connection_of_2_USB_power_gauges.jpg
psprsllel_connection_of_2_USB_power_gauges.jpg1168×557 97.9 KB

16

Aren't you worried about the voltage drop across the sense resistors that I mentioned? It will be significant at the current levels you're talking about.

17

aarg:
Aren't you worried about the voltage drop across the sense resistors that I mentioned? It will be significant at the current levels you're talking about.

Of course I care. But the usb power gauge measures that? Right? Also, I connected in parallel, so the same Voltage.

18

alex5678:
Can this work?

Probably. Not ideal though. Looks to be the electronics equivalent of using a hammer to bash in a screw to me.

Plus what if there's some kind of connection, or other problem with one of the devices? Now you've got 4A going through the other and probably a BOOM.

It's also limited to 5V. In what way is that "more flexible"?

19

According to the datasheet, it can handle max 2Amps each. If I use a superfast charger they can handle up to 5 Amps (> 4 Amps) @ 5 Volts. The problem is, when I want to measure the Amps/Voltage/Power from 2 different UART and there is a time shift, beacause when I run the code and put for example:

....
read UART 1
read UART 2
...

there is definetly a time between them even in microSeconds, so they do not measure at the same time...
How do I fix that? Thread programming??

Thanks

20

alex5678:
Of course I care. But the usb power gauge measures that? Right? Also, I connected in parallel, so the same Voltage.

What about your load device? If it draws 4A from a 5V supply, it would drop 200mV through the sense resistors. Can it run properly on 4.8V (maybe less if the 5.0V droops)? Will your measurements be valid at that supply voltage?