Passive NFC-bar for easy reading of cards by smartphone

This is a further development of my idea of ​​the stand for convenient work with cards.

I share with the community new developments in order not to spend money on patenting and not allow others to sit in the hay as a dog. I hope that my experience will be useful to someone.
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Your attention is offered implementation options for all occasions.

The challenge is the engine of innovation.
When working with a smartphone as a smart card reader, there are ergonomic inconveniences and limitations on the options for installing and fixing the device.

Goal is a better life
Move the card reading area from the back cover to a more convenient position, without making structural changes to the smartphone.

The solution lay on the surface
To make a substrate with a built-in antenna, which will transfer the magnetic field of the NFC reader to the upper part of the structure, it is much more convenient to apply smart cards.

So the following versions of the performance were born:

1. Desktop monoblock

Only for reading cards. It is more convenient from an ergonomic point of view - no need to take the phone in your hand each time. An external battery can be mounted on the reverse side, which will turn the design into an autonomous “long-playing” reader.

2. Automotive

The design is useful when installed in a bus or other transport, also used only for reading cards.

The phone does not need to be held in hand, it is always on charge and in a prominent place.

3. Mobile manual

The uniqueness of the design lies in the fact that in this design it is possible to read not only cards, but also bar codes from tickets. The strap is attached to a suitable case for your phone, the phone is inserted into the case and voila - you have a standalone mobile reader in your hand, similar to what the jig carry with you in transport, add only a strap to your neck. If desired, you can equip the design with an external battery to increase the period of autonomy.

4. Desktop spaced

It will be convenient in rooms with access control. For example, when the customer and the cashier are on opposite sides of the glass, the readout area is moved closer to the customer. In banks, they do this with pin-pad.

Schematic diagram of the NFC-bar

If you look inside, everything ingenious is simple.

Two connected in a closed circuit copper solenoid of thin wire, placed inside the slats in a special way. Solenoids have a special shape and size. General electrical specifications comply with the requirements of NXP AN1445. The strength of the magnetic field produced is within the required limits (0.3–3 G).

The magnetic field excites an electric current in the first solenoid, which in turn creates a specular magnetic field in the second solenoid. Its power is certainly lower than the original, but quite sufficient for stable operation, and with high-quality manufacturing of the bar - completely without complaints, and is within the limits recommended by the standard.

In the central part of the bar there is a window for the camera of the smartphone, which allows you to read bar codes without disconnecting it from the NFC bar. This feature is urgently needed in tourist buses, where not only contactless cards are presented for control, but also printed tickets with 1D or 2D bar codes. I plan to introduce this design in St. Petersburg double-decker. Now they use a smartphone without such a bracket.

The design and equipment of the product

A smartphone can be of any size, the body of the bar initially corresponds to the maximum possible size of a certain group of devices. The side edges of the strap are made with perforations, which makes it possible to break them off, thereby adjusting the width of the strap to the size of the smartphone.

Externally, the slats are made of fairly durable opaque plastic, mostly white. On the front side images are applied at the request of the client. By default, complete with slats are stickers indicating the reading area.

The brackets are recommended not to be attached to the smartphones themselves, but to hard cases suitable for them, which are purchased separately.



Thus, the possibility of hot-swapping a smartphone is preserved, as well as the appearance of the smartphone and warranty conditions for its operation.

Application in life

To date, my work has not been widely adopted for a number of reasons, however, even without them, the system works and shows good results, both on water and on land. The desire to make strips at least for your project - is, and there is a possibility, but this possibility is limited to the number in the range of 20-30 pieces. The process of making any industrial development was repeatedly highlighted in Habré, with the obligatory mention of the number of the rake, especially when it came to cooperation with colleagues from China. Therefore, the process may be delayed.

I will definitely share the results in the next article.

In an attempt to make a correct calculation for the solenoids - I found a useful resource with a calculator .

And finally, I ask you to take a survey. If the models are in demand, then I suggest to cooperate for their manufacture.