[ale] RFID Systems

Wed May 22 00:31:17 EDT 2013

The RasPi probably has enough hamsters to pull off a small application 
like this and it would be easy to power from vehicle power (12V-5V 
switchmode DC/DC converter).  Doesn't have to be too complicated but 
there are also plenty of 12V direct SBCs around with options like 
MiniPCI and the like.  Anything running some form of Linux should allow 
you to set up a wireless interface as an AP so that it can service 
anyone around the vehicle (assuming the wifi dongle can be put into AP 
mode so just pick one that can).

In order to do multiple tags at once you must get a reader and set of 
tags that adhere to the anti-collision standards (ISO 18593 and ISO 
14430 are a start but there's now several ways).  I hadn't looked into 
multiple tag readers when I was trying to set up the inventory because 
the physical chemical handling protocol doesn't allow for more than one 
bottle to be in motion at any time (safety and insurance against 
dropping a bottle if you try to juggle more than one).  However, for 
most of the readers, it should be specified how many simultaneous tags 
can be in the field without having trouble.  There's some smarts that 
need to go with the process and that's typically part of a reader system 
rather than the chip.  The system is what you're going to want so that 
all it spits out on the wire is a list of tag IDs (you don't want to 
have to code for anti-collision yourself).

The thing to look for in multi-tag devices is an inventory class reader. 
  Those are the ones that will invariably have the anti-collision 
features.  I did a quick search and found a couple.  One is an ultra 
fancy unit[1] from Intermec that bolts to a vehicle, the other is a 
Bluetooth wand that can handle 350 tags per minute[2].

[1]http://www.intermec.com/products/rfid2_iv7/index.aspx
[2]http://www.tagsysrfid.com/Products-Services/RFID-Stations/HHU-400-Inventory-Reader

There are certainly many other options, just look for an inventory class 
reader or anything specifying anti-collision features (tags per minute, 
etc.)  If you want to go with the doorway idea, you want what's known as 
a portal (not portable) reader.  These bolt over doorways, loading 
docks, etc. and read from far away as tags pass by.  The antennas are 
typically larger to get more gain for longer range.  Most of them are 
panels of appropriate size (depends on the tag frequency).  UHF tags 
(800-900 MHz) can use portal antennas that are only about a foot square 
while the HF tags (100kHz-20MHz) need large loop antennas about the size 
of the anti-theft antennas in stores.

On 5/21/2013 20:55, Doug Hall wrote:
> Wow, that's some great info. I was thinking of a small computer with (the
> hammer that I'm familiar with) a Ruby on Rails application which contains
> one table that describes the items, linked to another table for the unique
> data (where the unique RFID codes are), and perhaps a table for users, etc.
> Not really a difficult database. I might even use SQLite as the DB. The
> point of the app is simply to store what's supposed to be in the truck, so
> that when they finish a project and prepare to leave, they can find out
> what's missing. We could use the antennas by each door, and do the in/out
> approach, but I think it would be equally acceptable to wave a wand all
> throughout the truck, when they want to account for things, and have the
> application tell them which items, if any, were last scanned more than #
> minutes ago. I think that our project managers have iPhones, so they could
> be used to interface with the Rails App, and possibly with the wand (if
> necessary).
>
> The small SBC sounds interesting. I'm pretty sure they have power, but I
> need to get some more specifics about the environment. Your SBC with a
> wireless card is intriguing. I don't have a lot of experience with SBCs.
> (Just my Raspberry Pi.) If you can send me some links to the equipment
> you're thinking about (both SBC and antennas), that would be SO helpful.
> You sound like you've had some experience, so if you can recommend certain
> hardware that you've had success with, that would be awesome. A quick
> Google of SBCs give me too many options to be useful.
>
> Much appreciated!
> Doug
>
>
> On Tue, May 21, 2013 at 7:54 PM, Alex Carver <agcarver+ale at acarver.net>wrote:
>
>> A tiny SBC on the back-end is probably all you'll need to do live
>> inventory.  Put a wireless card/dongle on it and set it up for AP mode to
>> let any WiFi enabled smart phone, laptop or otherwise access it, no cell
>> connection needed.  It also would give you persistent storage which you
>> could save and transfer later to do things like determine what equipment is
>> used (or not used) and how (in)frequently it gets used (useful for space
>> management on the truck).
>>
>> The best thing for inventory is to put RFID antennas on the inside and
>> outside of the truck doors (one pair per access point to the gear).  As the
>> equipment enters and leaves, you get tag information and direction (outside
>> before inside, item going in; inside before outside, item going out).  That
>> makes it idiot resistant and doesn't require any user to actively think
>> about scanning/wanding/etc.  I was setting up a similar system for chemical
>> inventory at a semiconductor research fab.  The chemical bottles were all
>> tagged.  A bottle going into the chemical cabinet registered +1 inventory
>> and a user pulling out a bottle registered a -1.
>>
>> Some of the higher quality readers will report multiple tags at once which
>> means a Pelican case full of individually tagged items can all be
>> inventoried in one pass through the antennas.
>>
>>
>> On 5/21/2013 17:20, Doug Hall wrote:
>>
>>> I'm researching the use of RFID tags for inventory control for a truck
>>> full
>>> of expensive video equipment. At the end of a project, our employees need
>>> to be able to do a quick inventory of all the equipment on the truck, and
>>> be able to quickly account for its contents. Ideally, the system could
>>> leverage an iPhone front end but be served by an open-source back end -
>>> perhaps a Rails application that I can write. They may not have internet
>>> access, though. Sometimes the truck is needed in locations without
>>> cellular
>>> access. So, if the application could work offline, that would be great.
>>> It's not mandatory, though. Perhaps all I need to do is learn how to do
>>> local storage in html5.
>>>
>>> Any advice or suggestions would be welcomed - especially if you have
>>> direct
>>> experience with RFID. I've written an inventory tracking system which uses
>>> bar codes, but for as many (sometimes small) items as they need to track
>>> on
>>> this truck, that would take too long. Also, it can be a separate and
>>> simpler system than what I've done.
>>>
>>> Thanks for the advice.
>>>
>>> Doug
>>>
>>>
>>>
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