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I do computer support in our public library. Lately I've run into some issues with the RFID readers we use for our check out and staff stations. I'm trying to troubleshoot the problems we're having, and possible find another source for our antennas.

We use a Smartstation 200 Shielded Workstation from Bibliotheca. I can't seem to find a product page on their own website, but here's an outside vendor.

These come as two parts; the RFID reader that connects via USB, and an external antenna. The reader that ships with this set is a FEIG ISC.MR102-USB. I'm not sure who makes the antenna.

I currently have two different complete setups (reader & antenna) that are malfunctioning. We're having trouble getting help from the company we got them from, so I'm trying to troubleshoot myself. I took the faulty setups and started mixing and matching with ones that were working. I found that the two readers I had worked fine with antennas known to be good, but when I swapped in the two spare antennas I had in to our existing checkout stations they didn't work. So it seems like the antennas were the problem.

They'll each work properly for maybe 30 seconds, then the status LED starts flashing. According to the manual I tracked down this means "Temperature alarm, short circuit on antenna output". I'm not sure where to go from here.

I've gone over the wire that leads from the reader to the antenna and I don't see any visible damage on it. The only thing that looks a little sketchy is the circuit board inside. You can unscrew the metal plate on the base and lift it off, along with a plastic spacer, then you have direct access to it.

Here's one of the ones that's having problems:

enter image description here

Here's a newer one that's had virtually zero use:

enter image description here

Connection close-up:

https://i.imgur.com/66JZMg7.jpg

Obviously some of the solder connections have a sort of build up around them. I don't know if that could cause any issues. Both of the older ones look similar. Aside from that, I'm lost.

Any other brilliant thoughts about anything I could check, or test?

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  • \$\begingroup\$ We're having trouble getting help from the company we got them from, so I'm trying to troubleshoot myself. - you need to be more persistent on this. If they are a reputable company they will help. If they aren't reputable then why did you library use them in the first place? It's not rocket science to choose companies that are reputable in this field and it's something that you really might have to do. Just don't buy stuff from dodgy dealers or, companies with an unrecognized quality system or, when the documentation isn't that good (including service manuals). \$\endgroup\$
    – Andy aka
    Dec 31, 2021 at 9:22
  • \$\begingroup\$ Is the antenna a FEIG ANTS370? The problem could be as simple as a faulty antenna cable, but you'll need rf test gear to check this, or unsolder the cable and do a continuity check, or simply replace the cable - this would determine if the cable is the issue or something else. There are various companies that will assemble rf cable and connectors for you, but you'll need to understand what you're ordering or show them a sample and they should be able to make a cable for you. They may also be able to do the soldering. Google RF cables and connectors assembly. \$\endgroup\$
    – Kartman
    Dec 31, 2021 at 9:50

1 Answer 1

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(my guess is they use isolated dipole wires so a short is a problem but may work for 30 seconds, so locating the connection short is your goal)

This might surprise you but for near field , a piece of wire can be good enough for an RFID antenna to scana book, but a security exit needs two clever geometric coils, one on each side.

Of course there will be blind spots but a few minutes of experiment will tell you what works. Then a couple hours to optimize the sensitivity for the area and small gap it has to detect with some box or non tagged book gap to add margin for range.

But they also make large antenna for exits with double panels, so I'm not sure which antenna fails. The quick test could be an open circuit is OK with a $5 DC Ohm Meter and anything well less than 20 Ohms could cause this over-heating issue.

I have no idea what the antenna design looks like, as closed loops in a book or open dipoles in exits but I see several pairs of wire. The fatter wire just reduces the inductance a bit and makes it stronger. It's not for current, rather, just low impedance.

Imagine the surface of the antenna wire as glowing red and the orientation that is brightest will have the most sensitivity. Then tuning the length across the axis depends on the 1/4 wavelength per wire but isn't that critical unless you are on the very threshold of detection. They have one size to shield and the other to centre conductor on the left.

The antenna board is just for impedance matching RF and splitting the signal into two paths. It looks fancy and with low power might work for 30cm ~ 1m range. If locating the open or short fixes it, great. The white power is a result of copper corrosion and no clean low acid flux. Not great, as a non-insulator but probably not the problem, as it would show signs of heat stains in that region. It could be cleaned with rubbing alcohol and a toothbrush to look pretty though and maybe work a little bit better later.

The company who designed them I believe is in Taiwan, which may explain the lack of communication. Then someone else probably fabricated them so QA support is rather difficult for these small kiosk markets. But if your organization had more buying power , go thru purchasing to get their attention with the details you are providing us including failure rate, P/N and qty. And request "ASAP SVP Gracias ') (which covers 3 languages but the Taiwanese are pretty smart being the pioneers of LED & MOBO production.)

http://www.pnss.com.my/cayin.html ( not much help on site, except contact info)

Failing that to make a semi-permanent solution (assuming that works) you need what I believe is called an OSX coax receptacle to solder . You could make it a dipole with similar wire but hopefully your find that connector damage has shorted the tiny coax or some other open or short different in the antenna, while tested with the power off using any DMM in resistance mode.

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