Inductive current measuring using Raspberry Pi 

I have a Ph.D. in electrical engineering and I am very impressed with your knowledge. You really know your stuff! It is so refreshing to see someone who genuinely thinks about things and solves problems in a deep-manner. The more experience I have working with other engineers, the more that I am convinced that these traits are exceedingly rare. Most people do the bare minimum to get things done and are very surface level, making decisions based on their ego rather than focusing on the problem at hand. You are a treasure!

Alternate title: Man fails to create an electrical fire for 10 minutes

You can estimate how subtle the considerations are in a Matthias explanation by the number of nested "buts".

9.06. That is right in line with what we are taught as electricians when calculating fuses for motors. We are taught that most motors will surge with roughly 6 times the current of steady state. 70A/12A=5.83. So bang on! The same goes for the circular saw

10:30 You should lookup the trip curve for your circuit breakers. For example, if I look at the trip curve for a 'C' curve Eaton Breaker I see that it could let through 9 times its rated current (that's 135 Amps for a 15A breaker) for almost 3 seconds, however at 10 times rated current (150A) it will trip in < 0.02 seconds.

Depending on the breaker characteristic, it could trip "instantaneously" for anywhere between ~3x rated current to ~20x rated current. Look up the trip time characteristic curve for the manufacturer and part number for the breaker in the panel - there should be a point where it jumps in value from seconds down to milliseconds (it'll be a log-log plot, so it's pretty obvious)

As a retired electrician I found it very interesting and matches up to my real world experiences.

Great video! I love the journey toward simplified solutions.

Great video Mathias! I work at a national lab as an EE and I do a lot of hands on stuff like your doing there. It is cool to see how much you think out side the box.

fun to watch. love seeing you experiment with building your own stuff instead of always reaching for a COTS solution.

I've been an EE for a LONG time. When I was relatively new at the job, an old timer pointed out that if you want to get rid of "noise" you have have have an energy consuming element. IOW: a resistor. Non energy absorbing elements (caps and coils) merely move the noise energy about.

I enjoy watching these types of videos on this channel And I can tell that you enjoy making them as well Another great video keep up the good work

Every time i pop the breaker at home i get pissed and here is Matt trying to pop one on purpose .Love your channels

This is so helpful! I'm planning to work out some kind of a current monitoring setup and see how many lines I can monitor off a single Pi. This single quick video covered about a few months of research and experimentation that I would have needed to do otherwise. Bravo!

I've got a spare Raspberry Pi (well, 10-20), an Adafruit ADS1115, and loose ethernet cable...I should give this a try! Well also a chinesium ADS1115 and some split current-sense coils, as I intended to do a similar power-monitoring project already. :D

Pretty interesting indeed, Matthias! 😃 Thanks for the lesson! Stay safe there with your family! 🖖😊

I used to design inverters. I did similar testing, and the worst load that we had to deal with on an instantaneous basis was a compressor.

I had a number of ideas to measure the "mileage" of a thickness planer (or really any of our rotating tools). I think it would be fun to watch how much linear or squared feet of wood I've planed increase over time. Measuring the current jump with such a coil when the cutting head engages the stock seemed like the best overall method.

Love the video. lol. I need to update my periodic table. Chinesium is not yet represented. I had to replay the video. At the end…I realized you basically recreated THE FLUX CAPACITOR! You’re a genius Doc!

My question now is why don't they make a clamp on transformer that fits nicely over 12-2 or 14-2 romex? It seems plenty sensitive, and that way most of the branch circuits in a home could be monitored right out of the box.

Two things: first try to find characteristic (time-current curves) of your circuit-braker, what is important there is to notice that it is just integral from i^2*t on chart. Second measure voltage without and with some restive load (electric kettle is good). Then from current with load and the voltage drop on your cables you can calculate impedance. I don't know exact english transcription but it is something like: external loop impedance. When impedance is high with installation overload (or even shortcircut) you get hot cables (and fire in long time) without breaker trip (because with big impedence, current is not big enough). I am not sure that your fuses are well chosen.... I like your videos, so if you need something from mechatronic engineer just write me :)

I always though you knew a lot about electricity for a woodworker, then I watched your intervew on WWMM's podcast.

I used a clamp meter to verify that I was getting high spikes in the electric here. I found out both by capacitors blowing up and certain led lighting having bright flashes. Finally, they fixed the local transformer.

When there is a “dead short” there is a very high fault current. Much, much higher than what there is during an overload condition. Then the breaker will certainly trip.

Most circuit breakers have a graph of time vs current for it to operate. After many years of electrical engineering, I'd say that a crude rule of thumb would be that a breaker will open when the surge current is 10x the breaker rating. But I have to say again, this is a very crude generalization, consult the manufacturers data, and then add in correction factors for age of the breaker and for the shape of the initial current surge. :-)

You can often request a breaker datasheet from the manufacturer. There they show how long it takes for the breaker to pop at a specific current. The graph is hyperbolic and if the current is

Interesting video as always. Measuring current is one thing, but you don't know the phase of the current with respect to the voltage. If you measure that too things will get even more exciting. And as for circuit breakers, they are designed to prevent your wiring from burning whilst not nuisance tripping from inrush current. Check out the characteristics for these things, the amount of current needed to trip the breaker is strongly dependent on the amount of time this current flows.

I enjoyed that video. Watched whole thing in one go. Nice work.

The look @10:47 - that’s someone in their happy place!!

I understood temperature sensors and iPad charger from this video.

I have seen breakers stick closed when the inrush current was to great. It makes a terrible buzzing noise. It was a new installation, the neutral was wired directly to load.

All of these experiments demonstrate why you need to understand that I=C*(dV/dt) and V=L*(dI/dt) better than any of my college professors could.

Just note: Breakers, or even old ceramic fuses, are made in my country with various "speed" characteristics. For example 10A normal will hold just a few amps over and goes off almost instantly, while "slow" one (old ceramic ones had snail shell printed on) can take peaks from devices like engines for few seconds and still keeps on without going off instantly.

I wonder if the clone chip is based on the ADS1015 instead of the ADS1115. The 1105 is a 12-bit chip with higher sample rates. If the data interface of both is the same that's what I would bet on.

If you look up your circuit breaker make and model and find the datasheet - there are trip curves associated with time to trip based on current load. There are levels for May trip, must trip, and never trip. all in one convenient place.

Very nice... exactly what I was looking for

Mrs Matthias: "honey, why is the fuse box on the house on fire?" 🔥. 🙂

Great video. Very interesting. I've been interest in home energy monitoring for a very long time.

Matthias is now a member of the ThinkPad club

Call the fire department... Matthias wants to play with his Raspberry Pi....

What a fascinating video!

Wants to measure current in power lines. Matthias: Builds a complicated, safe, and effective system. ElectroBoom: Plugs in cut and frayed wires to the outlet to measure. Both are equally entertaining to watch.

If you're particularly fond of a spot of electronics development, a Rogowski coil is an interesting project.

Very good measurements. I will say this though, I don’t think the pi setup is quick enough to measure the in-rush current. I went through this on an aircraft in where they use 28VDC but they have a radar system that is powered by 120VAC 3phase. In order for this to work, they use three separate inverters that are synchronized together. When the operators would enable radars their monitors in the back would turn off and after a second or two turn back on. We did numerous load analysis tests on the aircraft and everything looked great, until we pulled out a more modern oscilloscope and tested across the main DC bus. When the radar was enabled, the 28VDC bus would drop to 0.0 VDC for 3 milliseconds.. yes, three milliseconds. The load analysis equipment we had would take at max 4 samples per second and didn’t see it. This short power interruption was caused by the capacitors inside the inverters. When first turned on, they act like a dead short across a circuit until they charge and therefore build resistance. I’d be willing to bet that circular saw alone would be 150-200 amps for that 0-5 millisecond range until it spins up and induces its CEMF (counter electromotive force) or back EMF into the windings. As always, I enjoy seeing your videos and it’s crazy what you have done with that Pi. It makes me want to get one lol. I’m building a project van and should get something like this or a DC clamp meter so I can do load analysis and such for figuring out what my load is on the alternator to make sure I’m not going crazy. Shouldn’t be too bad as I’m switching out to LEDs and whatnot. Keep up the great work!!

I love these videos. It reminds me that I am not as smart as I think I am and that I probably just hang around really dumb people. 🤔

Really great work.🙆🏿‍♂️

Interesting video Matthias. I'm always looking for "non standard" Raspberry Pi projects.

Amazingly, I even understood a tiny bit of this....

This is roughly how the 'Sense Energy Monitor' products work. They develop a sort-of fingerprint for devices that are plugged in and identified on the circuits into your breaker panel.

Really nice experimentation, thanks for time!

There are $10 smart outlets on Amazon that can measure current and are WIFI enabled. I’d probably try and use one of those with a pi but I love your DIY approach and problem solving. I recently bought an amp meter for the same reasons.

Wow, really neat. I didn't realize you could do this over the wire pairs, thought you needed a single conductor thru the coil, like that clamp on transformer you showed. I have been curious about Hall effect current sensors too, but have so far been too busy and too cheap to buy one.

I did understand a word you said.....'cept for chinesium.

Wow, what a fantastic video! Great content and so educational!

Hi Matthias, excellent work! I would suggest you try a coil transverse mounted to just one side of the romex. Thus trying to only sense the current in say just the black wire. Since the white and black carry opposite currents they are trying to cancel. Wind a coil and place it on the side of the romex.

Nice home made rogowski coil.

A few months ago my dust collector was failing to start and tripping the breaker. My first check was a current clamp meter over one conductor and it would get up to ~70a (120v) before tripping. And that's with a slow meter without a min/max function.

In Australia the short circuit trip current of a breaker is 7.5 times the breakers rated current. So if its a 16A breaker then the instantaneous trip current would be 120A. You should cut a wire to make it short circuit and see what current reading you get. Just use properly insulated tools

Great! Had fun watching it and learned something, thanks Matthias! :)

Yup, your first attempt made a high-pass filter. With a resistor in series and a capacitor in parallel you get a low-pass filter (and the much-cleaner signal on your scope).

in your dark blue coil you're wrapping the turns around the torroid of the loop. this will add noise to your signal. leave those out of the wrapping and use tape or something non-conductive.

Damn, i'm too dumb for this video. I'm a woodworker, not an electrician or engineer and wish I understood these videos from matthias as well as I do his woodworking videos.

If your coil had enough loops you could pass its output through a rectifier and filter cap to get a smoothed reading. More loops in the coil means more voltage allowing it to more easily overcome the forward voltage drop of the rectifiers and so it can be measured accurately by a lower-impedance device.

Very useful also if u have a wire like in europe. 3 in a triangle not in line and from exterior is a circle. The current transformer also not possible.

Great video, it had self propelled scaffold levels of evergy and fun haha How about making a self propelled step ladder for old times sake

You need the circuit breaker manufacturers tripping curve.

if you power your electronics connected to the Pi with a separate power supply it will help with noise a ton. Running them off batteries will work best for eliminating noise. The Pi has very dirty power.

The shield couples just one wire to the coil as long as it does not approach the centre of the current carrying wire. In the diagram the flux should be shown from the second wire going in the opposite direction. You may get better results if you wound the coil around the 'shield' which would then become a transformer core and then put the shield / core a bit less than half way across the wire.

You could use a extension cord with split cables to measure every machine. No need to split the cables of the machines.

Your lucky, my modern house distribution board pops the breaker every time I start my circular saw or drop saw. I need a circuit with a slower current curve for those high surge tools. I have to run them from my portable generator in order to use them at the moment. They worked fine in previous homes I lived in. Just newer electrical standards for wiring now.

A fun experiment. Thanks.

Funny, every time I started my table saw and shop vac at the same time it blew my 15A breaker or would tripped the GFI. I guess the arc from the vacuum motor is the cause? Annoying for sure.

Wow, your shop circuit is only 15A! And all those tools didn't trip it!

I like how your brain works!

This is some quality content.

The white is neutral wire and connected to the ground in the breaker box. The alternate electric flows on the black wire from the breaker.

you can film a CRT display by setting your camera shutter speed and scan direction to match the tv (or in this case, oscilloscope)

Might want to check the loop impedance on that circuit to get an idea of whether it is limiting your fault current. Would be an interesting detail.

Have you ever seen the sense energy monitors? They are pretty interesting but it is hard to swallow the initial cost. They can take awhile to pick up all your devices but it's awesome when you eventually get a lot of devices.

Instantaneous trip current is 6-10x rated current according to Schneider electric’s datasheet for square D style breakers.

That spike of current on startup is called inrush current.

Try two separate coils, one over the black wire edge and one over the white wire edge of the cable. Connect these coils in series in different polarities till you get the highest output.

rms of ac sq root of 2 time dc resistance gives you about 70 amp peak turn on of the plainer.

Did you try a hall effect sensor against the wire?

I used current sense transformers on each of my machines connected to an arduino to automate my whole dust collection setup. I have a vid explaining the details on my channel. I actually want to experiment using an FPGA instead of an arduino. Do you have any interest in FPGAs or Verilog?

If you want to make a current tansformer you need to put a load. Your coil needs to have a resistor accross it.This whay you'll get rid of the noise and actually measure current and not voltage that somehow depends on current, but also on other things

Now I'm very curious as to what is inside the split current transformer. I was under the impression that they didn't work unless closed. Quite interesting!

Its quite common for a motor's peak starting current to be about 6 times the normal running current. 12 amps × 6 = 72 amps

If you powered the ADS1115 off the 5V rail, than yes I suspect you would see noise due to whatever the RPi is doing. The 5V rail is unregulated. However, the 3.3V rail is very stable - try that

TIL: less flux reluctant magnetically permeable hysteresis saturation effects linearity

Cool Matthias! You designed a Sense energy monitor! LOL

I didn’t know breakers were that tough

The video shows your lights dimming for a fraction of a second as you switch on multiple loads.

Raspberry pi ftw

You should compare your results to the breaker manufacturer's Time/Current curves. Looked like a Cutler-Hammer/Eaton breaker. Check their website.

Great work!

This is a very practical invention. I don't expect the length of the pickup coil adds at all to the sensitivity. I would expect the number of turns to improve sensitivity. How would one connect two coils to provide a quadrature signal that will tell you the direction of current flow for when, for example, current is being fed to the grid or being drawn from the grid?

That was fun!

Aren't ferrite rounds used for cleaning up the electricity? Wrapping the romex around a suitable ferrite donut could help.

I'm enjoying this sort of content, but I'm weird. Could you describe some of the theory behind filtering noise from the RPi? I had constant issues with mic noise with my RPi. I was using USB sound chips. I'm glad you decided to look in to the clamp on style probes.