DIY Arduino power/energy meter 

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Ok... I have a bunch of things to say about this, as I recently tore apart and retraced one of the cheap Volt/current meters. I created a schematic and video about that device for reference. I suggest you take a look at it to help you understand a few bits. Those devices use a 3v3 regulator for the MCU and to power a LM358 which is essentially the dual version of the LM324, (not exactly the same but very similar). If you look at the circuit they use for the LM358 current sense amplifier there is a network of series resistors between Vcc, the op amp inverting sense pin, and the current shunt to ground. These are used to overcome the op amp's bias issues and get it into the linear region of operation. I had trouble replicating their circuit exactly myself, but there is an easier way. Just place any silicon diode, 1N4148, 1N4001, etc. between the output of one op amp and the feedback resistor. The op amp feedback loop will drive the output to compensate for the diode drop. This will put the output into the linear region and you'll get accuracy. Still don't understand? The op amp's output pin goes to the Anode of a diode (PANIC= Positive Anode Negative Is Cathode), then connect the cathode of the diode just like it's the output of the op amp. Next issue... I also tried several different combinations of multiple op amp stages like you did here. Don't do this. Your amplifying the error from your first stage. Do all of your gain settings in one stage. Once you compensate the circuit for linear operation you'll see it works perfectly and no need to try and rig code for none linearity in your op amp. Finally, your calculations for your shunt resistor are wrong as far as current ratings are concerned. You don't calculate a shunt resistor like a power resistor. Your not placing the shunt resistor in parallel with the load. Your placing it in series with the load. If you want to know the actual power rating needed you need to calculate the voltage drop at peak current. This voltage drop is the "Voltage" you plug into the equation to calculate the power rating needed. For example let's say you have PSU capable of 10v at 1A supplied to a load. This load is connected to the PSU positive output and to a 1 ohm shunt resistor on the common/return that is connected to the ground terminal of the power supply. In this situation, the shunt resistor is not connected to the positive terminal of the power supply. This means we can't calculate the power rating based on it's voltage drop like a power resistor. This should make sense if you think about it. *Your trying to amplify this voltage drop in order to calculate the current of your circuit. If the voltage drop across the resistor is the power supply voltage, what the heck are you trying to measure and amplify?* The number your trying to amplify is the actual voltage number you need to use to calculate the power rating of your shunt resistor! You know this number is tiny and fairly linear, but obviously this changes in the circuit and you still need to calculate the power rating for your shunt resistor right?!? How do you do this? It's very simple and easy. You need to know the maximum current your power supply circuit can supply. In my example above, (10v at 1A w/ 1ohm shunt), you know you have 1A across a 1 ohm resistor. This is going to create a 1 volt drop across the shunt resistor when there is the maximum of 1 amp across it. This means that the shunt resistor only "sees" 1 volt at 1 amp, so it will dissipate 1 watt. The big mistake people make is calculating a shunt resistor as if it's a power resistor, aka the resistor as the load/as if the whole power supply voltage is placed across the shunt. If you did this *wrong* like many people do you might calculate 10 volts across 1 ohm is 100 watts. That is how you calculate power resistors/a load, but it is totally incorrect for calculating resistors in series, aka shunt resistors. The other problem people tend to miss is that the load is going to see the same voltage drop in the circuit as the voltage drop of the shunt. This means that at 10 volts and 1A the load is only getting 9v due to the 1 ohm shunt's 1volt drop. You can build your power supply to compensate for this or you can use a tiny shunt resistance value that creates a very small voltage drop. If you think about it, with our 1 ohm shunt resistor example, you don't even need a current sense amplifier. You can use the internal reference of the AVR and set up the ADC to read from 0-1v. Choosing a lower value shunt resistor allows you to minimize the effects of the shunt resistor voltage drop, but the voltage drop is too small for the ADC to measure and therefore you need a current sense amplifier. This type of common/return shunt resistor is still very crude but it is reasonably accurate and enables you to use cheap jellybean op amps. Better designs work on the positive terminal but that requires a much more advanced differential amplifier configuration...I think... that's one I want to explore more and test out soon on my bench. Hey, at least you didn't etch something yourself on a tiny SMD PCB just to learn about the bias current and none linear op amp issue. You should be able to add a diode to your protoboard design easily and fix the problem. -Jake

a pcb track can be used as shunt. Recently I made a usb V/I meter using an op amp without μC. Its gain is so adjusted that a multimeter can show the current value in terms of Voltage. This way we can reduce the effect of the meter cable resistance

@Electronoobs is it possible with higher voltage and current? I want to build one for my van to see how much Amp hours I need. So max. 14V and 150A. What I have to change? Only the shunt and the settings in the program?

Excellent video, almost exactly what I was looking for. But is there a way to use this power meter (could be slightly changed) and give a constant output of 5V? And what is the output power?

Plz do a esp8266 with Arduino tutorial in your style As you explain stuff very well

HI, how would i go about coding the eeprom to store the data and remeber it when power is switched on again?

hi! can i use 10 ohm 115 watt ceramic resistor for measuring hight current up 100amps?

can you please explain the formula used to get the energy?

Will you please help me to find the power factor using Arduino in order to calculate the AC power?

Hola, hace un tiempo intente hacer esto para adaptarlo a mi fuente variable. Pero no estaba conforme con la resolucion y precision del arduino. Asi que termine usando el arduino mas el ina226, y quedo perfecto. Saludos

ma dude ...your editing is on point !!!!

I'm curious to know what's inside of that 'Time Travel Stuff' Box 😐

hey there, really awesome project, wonderful to point explanation, the only thing i felt missing is designing a proper 3d printed case, i mean you even made this portable by powering the circuit via Li-Po , you could had made a practical Multi-Meter Style box or something that is humane to hold, anyways, this is awesome, cheers to great work!

Works with White Blue color 128X64 OLED LCD LED Display Module For Arduino 0.96" I2C IIC Serial new original?

Hello electronoobs, this cool video. How can i get 121 OpAmp gain? Thanks

Hey,well I should visit Spain or not.There is bigass summer here in India.🍉🍉🍉🍉🍉🍉🍉.How is the weather there electronoobs.

please make a video on wirelessly programming of arduino using hc 05

Can I use this to measure eanergy form an wall out let isialing 120 vac

Hello my friend Excellent video. I would like to measure 600v, 10amps please tell me.If i can change only the resistors in input;

Enjoyed the video I have recently tried the same setup, i tried using an 3 op amp instrumentation amplifier. Still a work in progress. You used a massive shunt resistor. That 100 watt resistor would go to 100 Amp with proper cooling. I used a 0.1 ohm 5 watt shunt resistor that will easily measure up to 5 amp at 2.5 watt. Kind regards

Awesome

Great video keep up the good work but in order for everybody to enjoy your videos you need to learn the correct pronunciation of the word current thank you.

Can you make a multi meter

I am santosh, i use to see your video regularly, also trying the seme ckt. With code , but when try to made this project, all is fine only when i don't apply measuring voltage & current, still there is some reading on display like, 0.244V. & 0.026A , so how to solve this problem ?? Please guide me to solve this problem. Santosh

good

yo can you do a how to video for diversity video reciever rx5808 module ?

I hope you're using magnet wire for those crazy homemade resistors.

Very nice project, thanks. BTW: The tang on the screw terminal can slide into the next one, so that they lock together in a straight line, instead of jamming together at an angle as shown.

Excellent project

otro excelente video...

Awesome project! Why did you use two opp amp inputs rather than just changing the resistor values for a bigger gain on one opp amp?

Can I buy it?

Plz, make a 18650 li-ion battery capacity tester

Really awesome job, man. That way should be easy to make a 18650 batteries tester. 😊

I had no idea that the "Spinal Tap" Joke, "ours goes to eleven!" was based in electronics... the op-amps each have a gain of 11.

great video !!

It is not ok to have a current shunt as a coil. You have to wind is such manner to cancel the current, in this way it is not reacting like a coil. Have a look on ElectroBoom channel too see how to make one. Although a very good video about power meter. Keep up.

great scott has made a better one over one year ago.

how to make an arduino uno hdmi shield?

Porque no haces los mismos videos del canal en inglés en el de español? Es más! Tú debes hacer un guión para tus vídeos, cojes el guión en español y lo agregas como subtitulos en RU-vid

may I use it for 230v also?

Excellent video. I’m going to build one of these. I’m looking forward to some videos showing things In your "time travel stuff" box :)

Why did you use two series amplifier instead of using one with higer gain?

No have AH

Is there any comparison between atmega328 and Intel 8086?

Where is the code for PowerCalculation? i cant find it :(

I built a system almost identical to this as a part of my ebike controller. Just that I use a 50 w 0.01 ohm resistor, a different op amp gain and a nokia spi display. When the system is measuring 0-10 A it is relatively accurate but when the current goes to 30+ amps it shows almost double the true value. Any ideas ?

What is the maximum power it can measure ??? Without any heat dissipation in ckt

NICE!!

I want to measure 220volt AC of my house. Should I use voltage divider?

I think this setup will not be accurate at all. As the battery voltage changes, the internal voltage reference for the ADC will change as well, and because the ADC values are referenced to the voltage reference (as the name implies), you will get a value proportional to the battery value. This could be solved by adding a step-up 5v regulator to be sure that the input voltage for the ATMega328p is always the same.

Thanks.....I have learnt many things noobs.....and way present is awesome man....👦👦👦

Wondering if you would be interested in a project! Please DM me

How to use 16x2 lcd instead of OLED. Code please. Thanks in advance.

but when you coil the wire then it becomes a inductor and filters out the signal

Turn it up to eleven? Good idea.

Andrei, you are not terminated not used opamps in 324, again... This can cause excessive energy consumption.

I would like to ask you something please if I may. So...... Is the schematic correct as shown above @ 4:45? And is this high side or low side? You are explaining this as if it is high side, but your circuit DOES NOT MATCH. You have the resistor in parallel to your load can you please fix this? This is VERY confusing, PLEASE PLEASE PLEASE, fix it. On the web site as well, you are confusing people whom you are supposed to be teaching, we all make mistakes and it is not a big deal to say sorry and fix it. as this video is so old maybe you can do an update on this specific video and link the update into this video's description? I don't mean this in a negative light but as constructive.

What happen to our brushed Motor drone

If you gonna measure current values up to 1A and uses a 10mR resistor, the resistor dissipates only P = R * I^2 = 10mW. The 10mR x 10W resistor is only necessary if you going to measure I = sqrt(P/R) = sqrt(10/0.01) = sqrt(1000) = 31.6A!!! I didn't understand why you said those specs for the shunt resistor on the video.

the wrong readings are probably caused by the offset voltage of the lm324 also

Hi bro ....good job man ....really awesome project . Dude i want to make 3ampr current booster .what i do ? .please help me bro . I want to make small 3ampr current regulator for brushed drone . Can u give me a great circuit form google.

Hola cuando veremos volar el minidrone?

I generally like your videos, but the "schematic" at 4:46 in this video leaves me disappointed.

So...what's in the 'time travel stuff' box? Haha

The cürent.

Kurent

You're trying too hard to produce content like GreatScott!'s

I hate the way you say currrent, you are doing it wrong man....

All this complexity to measure DC? Sorry, your effort is good, but that's some rubbish design.

You copied idea from great scott

It would help if you would articulate better, sometimes you slur your words and it makes it hard to understand u