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This Is The Year Of PCB Inductors | Hackaday

tags104 smd resistor

We have told this story dozens of times. In the past fifteen years, the cost of manufacturing a small number of circuit boards has dropped sharply, which has allowed people to conduct some interesting experiments on the functionality of PCBs. We have seen this on artistic PCBs, and also on the shells made of PCBs. This year we have seen some experiments on putting coils and inductors on PCBs.

At the forefront of these experiments on PCB coil design is [welcome], and he has made brushless and linear motors using only tiny copper traces on glass fiber. Now he is experimenting with inductors. His work recently won the Hackaday Award

, This is a simple circuit, but it needs an inductor to work. If you want to give an example of a method where copper spirals can be used on the PCB, it is more suitable than this project.

The idea is just to make the Joule Thief Tour. The circuit is not complicated-you only need a transistor, a resistor, an inductor or a transformer to increase the voltage on a dead battery enough to light up the LED.

The trick here is that [bobricious] does not use wires wound on ferrite or off-the-shelf inductors, but uses 29 turns of copper wire with 6 mil traces and spacing on the PCB. Any board room can do this, that's for sure, you can technically reduce the BOM cost of the Joule Thief circuit, but it will take up board space. This year is the year of PCB inductors. What else should creative PCB trace design do?

Stupid question-can you use a certain ferrite material in the middle layer to make a 3-layer board and use vias to "wind" the traces around the outer 2 layers, thereby reducing the footprint?

Or just stack layer after layer of coils between the layers of the PCB?

In fact, I have seen this and added some flat ferrite to the outside. You still don't get super-good density, but it is still cheaper than winding and mounting the core. Imagine a ferrite, which is like a magnet in a refrigerator, with scotch tape adhesive on one side, and you are there.

This technology is usually used at higher frequencies that do not take up much space...

Ferrite (or iron or iron powder) must pass through the coil, otherwise nothing will be done. How much iron is placed on the iron sheet (in terms of cross-sectional area) is a trade-off between the area occupied by the iron sheet (subtracted from the available copper area) and the increase in magnetic flux density obtained by the iron core. In commercial equipment using PCB coils, the powder iron core is usually two pieces, one of which is E-shaped or C-shaped, and the other is the same or flat. Only one end of C or the middle of E passes through the coil. The other end is wound on the outside of the coil, just like a discrete transformer or iron core inductor, but the winding is completed as a PCB trace instead of an insulated wire.

If that is true, there will not be any ferrite support on the wireless charging coil. It must be in the magnetic field so that it can participate, but does not have to "pass through" the coil.

It does not have to go through. If you want a larger inductance, it's best to have it on both sides, but it can also be on one side. Think about what these fields do. Just like the difference between a microstrip line and a stripline transmission line. air-and-fr4 and fr4-and-fr4.

You can use a ferrite core that passes through the PCB hole, called a planar transformer or inductor. A few years ago, I designed a DC/DC converter using this transformer, and the result was very good coupling, very low leakage inductance and a flat design.

On the other hand, you can use a thicker PCB, have a smaller toroidal core in the middle milled part, and leave traces and vias as windings throughout the stack. Murata NXE1 DC/DC converter uses this technology to search it as a picture.

Check out Murata's NXJ1 series of DC-DC converters – it is a very thick PCB with a ferrite core in the middle (inserted before applying the top stack), with traces and through holes to make windings. Very cool. I am surprised that their single price is only US$3.50.

How does the cost of a larger PCB compare to the cost of a discrete inductor? The PCB area is usually not free.

Inductors and transformers are among the most expensive components, but yes, they must be considered on a case-by-case basis.

The cheapest PCB manufacturers offer fixed prices on any board under 10cm x 10cm (4 inches x 4 inches).

Keep your board below this limit, the inductor is actually "free".

If the Schottky diode is connected in series with the LED, the frequency can be increased to a very high frequency, so that the required coil is much smaller

This +++

The 48V Telco quarter-brick power supply must be made with at least PCB inductors (at least 12 to 20 layers).

*With flat PCB transformer.

I think I used it for the first time about 15 years ago.

The flip point is made by some manufacturers using PCB coils.

Unlike more classic wire-wound coils, they have a lower operating voltage and a higher operating current (in return).

But they are lighter and cheaper.

Is the inductance of a "space filling" curve (e.g. Moore curve) (

) Is somehow reduced significantly (maybe even 0.0)? Because the advantage of this is that the two leads are adjacent to each other on the same side of the circuit board.

(Damn) s /Significantly reduced/Significantly reduced inductance/

This will result in a rather complicated magnetic field. I suspect it is not very useful in this application due to interference fields. Generally, you want the magnetic field of each coil to increase to the previous magnetic field.

The inductance of the coil is proportional to the square of the net number of wires running in the same direction. Therefore, whether it is a proper space filling curve or a positive oblique square tooth, any given inductance level will be eliminated by another inductance in the opposite direction.

If you look at any low-cost electronic products, such as mice or wall chargers or toys, they will not use PCB coils to make inductors and transformers. The small power ratings that can be achieved with this structure can be made with slim, inexpensive components, and the final circuit board area is small, so they are suitable for being packed in small packages.

This is an interesting idea, useful for educational or "wizard" purposes, but has no practical meaning in actual products.

This may be impractical, but it is feasible, and due to some publicity, it is safe to say that we will see it in actual products! :)

Many people don't realize how cheap small unshielded inductors are. I even brought a bag of through-hole small holes, and I spent a few cents each. I hope that what people do will not accept extensive testing and spend a lot of time designing on these PCB inductors, without even looking at the prices of all the inductors in stock in order of price.

My experience with using cheap inductors in DIY projects is that I am interested in saving more money when ordering parts, but when I make something, I actually don’t mind spending $1 on a good inductor . There are too many cheap inductors in my parts box to imagine PCB coils :)

It depends on power and frequency. You will see very common etching inductances in RF circuits. In receivers and high-frequency transmitters, the skin effect comes into play, and most of the current in the inductor can flow through the gold plating. The inductor etched on the PCB is definitely not the curiosity of the laboratory.

Please correct me if I am wrong, but isn't that the inductor shown in the photo above the transistor? I made hundreds of joule thief circuits, some of which can light up hundreds of LEDs with a single AA battery, and also used green-like inductors in the photos. A similar circuit is used in the circuit that powers the garden solar light, and this is where I got it. Does he use one wire wound on the PCB and another wire wound at the same time? This confused me.

This is a high tolerance resistor. It's not really needed in this application, but maybe this is what he has appropriate value on hand.

Thank you Brian. I have several inductors that look exactly the same. In addition, I am easily confused, haha.

In this case, it appears to be a resistor to reduce the current flowing to the base of the transistor.

Yes, all of my JTs use resistors, and some of them use variable resistors. I think I have never seen high-tolerance resistors, and inductors look a lot like them. Thank you.

I think this is a 560 ohm 1% resistor, which limits the base current of the transistor. Axial inductors similar to resistors usually have a brighter green body.

I remember that I have seen PC tracking inductors in various radio kits since the late 1970s, so I'm not sure if there really is such a year. Although these usually work a few turns at VHF, they have a correspondingly small inductance. Compared with many other inductor designs, they tend to have larger winding capacitance and lower Q, which is a problem to consider. There are still these neat things, they are "built-in" in the card, and it makes sense to use them when there is no problem with a large area or even when they are not needed.

Is this a good starting point for understanding stripline and microstrip lines?

Your circuit works in the kHz range. I have seen articles about building commercial FM antennas on PCBs. Although I suspect that microstrip lines etc. will be more effective above 400MHz, it will be interesting to see a mix of traditional and stripline designs around 140MHz.

Why not just use mounting screws as inductors? I don’t know, but it’s still on the periphery.

Don't forget the PCB Tesla coil from Megavolt.nl.

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