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Multiple RFID readers access control system

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songbreaker View Drop Down
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    Posted: 11 March 2010 at 6:45am
Hello fellas,

I am sorry if I post this on wrong sections, could not find suitable one. Feel free to move the threads if you think it is unsuitable here...

Let me start by introducing who am I, what am I doing and how I ended up stumbled upon this awesome site.

I am a programmer, I have quite strong programming skills, be it in C++, C# or any other C-derived members.

Recently I am promoted to lead a project for a newly opened community college. Mind you this college is funded by state and...the state is happened to be not so rich. Well our state needs the college so that we can educate students from average income families.

The college is so new that we don't even have any attendant recording system. I was instructed to develop an RFID based attendant system that records students attendance when they enter the class.

Now, I have developed a single terminal RFID for smartcard data access by using EZWave reader and it was in C++. It was awesomely fun experience. The system contains a reader attached to a PC by serial port.

Back to the project. The proposal requires that each building has multiple access points. I can do that as same as previous system but it is gonna be so redundant and costly. If I am to follow the previous one, there is going to be one PC for each RFID reader..which I somehow think not so effecient..

So the question raised.. Is there something,somehow that I could do so that in a building I could have multiple readers controlled by a terminal?

Thanks in advance.


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amal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 11 March 2010 at 10:00am
Originally posted by songbreaker songbreaker wrote:

The proposal requires that each building has multiple access points. I can do that as same as previous system but it is gonna be so redundant and costly. If I am to follow the previous one, there is going to be one PC for each RFID reader..which I somehow think not so effecient..

So the question raised.. Is there something,somehow that I could do so that in a building I could have multiple readers controlled by a terminal?
 
Hey songbreaker, welcome to the forum. Check this out; a new reader just released a few days ago that supports both XBee wireless communications as well as a multi-reader communications protocol which allows one PC to communicate with up to 255 readers on a single serial COM port. Furthermore, you can connect multiple buildings together under a single PC using the XBee carrier board to a USB network device server (assuming the buildings are networked).
Amal ;)

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songbreaker View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote songbreaker Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 6:11pm
Wow, 255 readers on single serial COM port? I never thought that could exist! LOL

That really helped me alot. However I do have couple questions regarding the product.

Let's say the building has multiple floors. Is the wireless communication still reliable in the situation ?

Also, is there any options if I want to do have the readers wired but at the same time without having too much difficulty in case if the wireless communication deemed unreliable from signal interruption?

I am really amazed by the xbee wireless communication.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote songbreaker Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 6:17pm
I forgot to ask regarding the readers programming side.

I have reviewed the specification and APIs provided. Supposed that I do not really want to use the .NET API, does the reader come with low level protocol manual so that I could develop my own API?


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amal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 6:22pm
You can get special XBee modules that have what's known as the ZigBee protocol firmware loaded in them. These allow for a mesh network in which each node (XBee module) in the system will form a mesh and forward messages for other nodes. So, let's say you've got a node at each end of a giant 1000 foot long hallway. There's no way those two nodes could hear each other, but you place mode ZigBee modules in between, and they will all forward messages for each other, allowing each node to talk through any other to reach the target node. The only bummer is, I have no idea where to get ZigBee modules and have never played with them... but from what I hear they do have the same pinout as normal XBee modules, so you should be able to plug them straight into the RedBee reader without any problems.

There are also high power XBee modules that have an increased transmit power and thus boosted range, but I doubt the voltage regulator on the RedBee will support the additional power requirements. You'll probably burn out the RedBee voltage regulator if you plug one of those in... but I'd have to check to find out for sure.

Aside from that, if you use normal XBee radios, you'll have to test the deployment area and put more carrier boards in the deployment area.
Amal ;)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote FourQ Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 6:23pm
Originally posted by songbreaker songbreaker wrote:

Let's say the building has multiple floors. Is the wireless communication still reliable in the situation ?

Do many people at the college leave by jumping from the first or second floor? Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 6:26pm
Originally posted by FourQ FourQ wrote:

Originally posted by songbreaker songbreaker wrote:

Let's say the building has multiple floors. Is the wireless communication still reliable in the situation ?

Do many people at the college leave by jumping from the first or second floor? Wink


Hahah well it is college :) But I'm actually deploying these readers in a two story building as a simple universal access control system (both internal and external doors), and I'm facing the same issue.
Amal ;)

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amal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 6:29pm
Originally posted by songbreaker songbreaker wrote:

I forgot to ask regarding the readers programming side.
I have reviewed the specification and APIs provided. Supposed that I do not really want to use the .NET API, does the reader come with low level protocol manual so that I could develop my own API?


There are serial commands listed in the manual, and the serial protocol was designed to be very simple. Just open the COM port at 9600,8,N,1 (no flow control) and hit enter. You'll actually see a > prompt. The commands listed in the reader manual should be fairly clear. Of course, you can post any questions you have here :)
Amal ;)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote songbreaker Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 6:32pm
Yea..nice point lol you got me there :P .  I hope no one jump out the building or else...man i hate seeing dead body in my workplace! :P

I was thinking if the project might included access points to rooms in the building. In that case.. I was thinking if every floor requires a terminal? I myself never involved in wireless communication project before so, my knowledge for its range is soooo limited. 


Just to clarify the zigbee you mentioned is for wired one right?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 6:38pm
Originally posted by songbreaker songbreaker wrote:

Just to clarify the zigbee you mentioned is for wired one right?


Nope :) The XBee module is a wireless module that plugs into the XBee socket on the RedBee reader. It enables the RedBee to communicate wirelessly. The XBee modules have their own firmware and run their own little microprocessors. Normal XBee modules can only talk to other XBee modules within range. Therefore, if you have three XBee modules (A,B,C) and placed A at 0 feet, B at 100 feet, and C at 200 feet, then XBee module A could not talk to module C because the distance between module A and C is 200 feet, which is too far.

However there are special XBee modules that have ZigBee firmware on them. The ZigBee firmware enables a special "mesh" mode that will allow module A to communicate with module C through module B. When module A sends out a packet for module C, module B hears it and recognizes that the data packet is for module C, so it forwards the data packet to module C.

As I said though, I'm not sure where to get XBee modules that are loaded with ZigBee firmware.
Amal ;)

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