Making a Current Transformer from Washers

This is a tutorial showing how to make an AC current sensing transformer out of a handful of steel washers.
We also do a deep-dive into the design of signal processing circuitry to make our washer transformer into a useful building block.

You can download the schematics here:

[kmxu]

It is amazing how well you convey the lessons learned from decades of experience!

[BusinessCat]

Forbidden pineapple slice. I really love how you explain this. Really clear and concise. Thank you

[ats]

I'm not crazy about using washers when much better cores are easily available from broken electronics, but I learned about using a winding shuttle from this video, and that will save me countless hours going forward. Thanks!

[proteekbasu]

Would like to thank you for this wonderful work, I am working on a wireless mains monitoring device and wanted to build something similar for monitoring the a.c. mains, came across your video but I had LM324 available that is pin 2 pin similar with 6024, instead of 75k 1% used 82k that was readily available, it worked like a charm and fulfilled my requirements.

[MrHvfan]

Really enjoyable video, its been years since i designed an analogue circuit that had to eliminate the diode forward drop, id almost forgotten the frustration and then the euphoria of solving it- great project, looking forward to watching some of your other videos

[NoNiceUserNames]

Great videos. Wish I had found them earlier as you fill in a lot of practicle gaps in my knowledge

[tonyfremont]

I love those microchip opamps. Some even come with a built in divider for a virtual ground reference.

[JonPrevost]

Liked and Subscribed. I think your explanation is great when working with hobbyists, but not so with students studying to become engineers or experimentalists. These road blocks are not insurmountable within a learning environment that is designed to test their fortitude and critical thinking skills. For those of us trying to introduce more people into electronics, I completely agree with your take on using better parts. One might say, more integrated integrated circuits ;)

[cap_fearless]

You are amazing builder. Glad I stumbled upon your channel.

[Chris_Grossman]

Using the washers is an excellent idea for a low cost AC transformer. I will probably use this idea in a future project.

[NotMarkKnopfler]

I really can't thank you enough for this video. You have solved all the problems that I anticipated - I have been thinking about how to solve this for days and was stuck on the Vf loss of the rectifier diode. But you solved it. I'm just getting started - I'm a software engineer by trade but I'm enjoying electronics *so* much! Thank you again! 👍

[mmoci]

Looking forward for a new lessons. Those kind of videos are great for beginner. Subscribed

[chrisfreitag]

Nice explanation. It would be great if you could zoom in on each section of the schematic.

[benjaminscherrey]

Definitely agree with your advice of using components that have really reliable and flexible behavior when getting started. The only thing missing from this video is some background on the AC side of things. How do we know to do 100 turns of wire on the washers? Also, what range of AC inputs will this circuit work with? Thanks for the cool video.

[accountant]

Thank you Leo, this is a great job and a very interesting video.

[EdwardKilner]

Subscribed. Very nice video. It’s been decades since this old EE did anything with circuitry. Nice commentary on $2 op amp. Can you imagine the cost of building that from discrete components?

[samsami]

many thanks dear, great video, , i hope you can do something about the shunt resistor and an OP amp, to make a current monitor or current limiter, specially if we can read that current using a 7 segment display.

[MyProjectBoxChannel]

Just a layer of clear lacquer or paint is probably enough insulation to prevent eddy currents. Sometimes the oxides on the metal is enough.

[freeenergytransformer]

When you need to measure a current and don't have a current transformer, there are a few ways to make one. One way is to use some common household items. For this example, we will use two washers.

Take one of the washers and bend it into a loop. The hole in the middle of the washer should be facing downwards. Take the other washer and do the same thing, but make sure that the loops are facing in opposite directions (one clockwise and one counter-clockwise).

Now, take some wire (preferably with insulation) and twist it around each of the loops a few times. Make sure that there is enough wire so that you can connect it to your voltmeter or other device.

[reetesh_bpg]

Really loved the video. Can you please help me with constructing a 'Rogowski coil'.