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RFID BASED ATTENDANCE SYSTEM +TX ,RX[9/9/08]

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ramdasi vaibhav

Tue Aug 19 2008, 06:53AM

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I would like to use a transmitter to transmit the attendance collected by system to a remote pc instead directly using rs232 connectr.
The remote computer would be almost 400-500meters away from classrooms.
Will it do?
If yes then which transmission protocol should i use?

[ Edited Mon Sep 08 2008, 08:51PM ]

say2paul

Tue Aug 19 2008, 07:21AM

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RS485 . .
It is successor of RS232 and can cover distance upto 1200 to 1400 meters.

I request Arun Kumar to further help you on this...

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ramdasi vaibhav

shyam

Tue Aug 19 2008, 10:40AM

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well i dont know ...
but can RS485 be used commercially ... is it open source...
i am talking about the networking protocol ahead of RS485!

lProgress is not made by early risers or hard workers, but by LAZY people, trying to find easier ways to do the same........

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ramdasi vaibhav

say2paul

Tue Aug 19 2008, 10:41AM

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Don't know buddy, but Arun recommended me the same..

So lets wait for his reply!

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ramdasi vaibhav

shyam

Tue Aug 19 2008, 10:47AM

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what Arun recommended u was make ur own RS485 protocol!

but i want to know if RS485 protocols like siemens MODBUS etc.. are open source and can be used for commercial/hobby products!
hope arun will give the exact idea...

all i know is this

RS-485 is a physical layer electrical specification, not a communications protocol. RS-485 uses two wires and differential signaling (ie voltage differences across the two wires), and be multidropped to allow multiple devices on the network. Modbus-ASCII, Modbus-RTU, and Profibus-DP are three examples of protocols which use RS-485 as their physical layer.

ref:

http://www.rs485.com/rs485spec.html

[ Edited Tue Aug 19 2008, 10:51AM ]

lProgress is not made by early risers or hard workers, but by LAZY people, trying to find easier ways to do the same........

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pdi33 , ramdasi vaibhav

Arun Kumar V

Tue Aug 19 2008, 10:55AM

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Hello Vaibhav,

your thread says "RFID" and in your post you ask " transmit wireless using RS232" ?

anyway i'll brief you how its done : RFID reader reads the RF tag at particular freq. and sends it to the Micro, micro displays the Tag info on LCD and sends it to PC for database storage. there'll one RFID reader and many RF tags ( in the form of Student Ids).

Now RS485 protocol which, paul was talking helps in a Multiprocessor/controller scenario (1 master and more than 2 slaves), since in you case its only one micro and one PC, RS232 can be used with help of 433Mhz RF modules ( range 300 meters in open air) for longer range ( as in your case) you have to go for Hi-power Transceiver ( 1Km range)

before we go further, let me know your opinion

Arun

[ Edited Tue Aug 19 2008, 10:58AM ]

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ramdasi vaibhav

ramdasi vaibhav

Wed Aug 20 2008, 09:00AM

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Sorry for the delayed post and thanks alot for earlier replies!
Now, let me explain u what i would like to do:
1.I want to do project RFID attendane given in download section and want to implement that for my dept.
2.I want to do one modification in the given project.
-Instead of storing database directly in th pc connected using rs232 i/f,i wish to transmit collected data (attendance) from uc,wirelessly to remote pc situated in the dept.
3.Now,the problem is:The classrooms are quite away from my dept.To be exact-
My claarooms are on groundfloor and dept is situated at around 400meters,in another building ; that too on second floor.
4.If the dept and classrooms were nearby each other,i wld have used zigbee modules(i guess?...).
5.So for these physical tx and rx locations,which type of transmission sceme should i be using for faithful database storage in remote pc.
( Plz do rectify my ignorance bcz i didnt have practical knowlg but wish to enhance it)

Ajay

Wed Aug 20 2008, 01:29PM

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well thinking about your requirement, i would just answer for point 2,3,4

well its possible to transmit data wirelessly to remote PC but distance is the problem, in your case you are considering 400 mt displacement, where as there is shift in floor too. which makes a lot of difference.

zigbee modules are good, but they may be complex for this simple data transfer application. So you can look for basic wireless modules like 433Mhz, 868Mhz or 2.4Ghz all are ISM bands.
your one unit is on second floor and other on 2nd floor, so depending on distance in two buildings (considering two floors parallel) and then distance between ground and second floor, so it may be possible that you need multiple wireless modules to meet these distance conditions.

--> One simple solution

read data on local PC where your attendance is being taken, then transfer data from that pc to other PC in second building via LAN (local area network) which is available everywhere in colleges.
you can make a simple VB application in which data can be transferred from one PC to other PC. All you need is simple winsock based application. as its LAN so speed will be fast enough.
I hope this solution can resolve your problem, and will make your application place independent (within the LAN).

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ramdasi vaibhav

ramdasi vaibhav

Wed Aug 20 2008, 10:50PM

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Thank you ajay sir for your reply.
Your suggestion of LAN is appreciable but my guide insisted me to use wireless transmission.
Also my classroom hasn't got the pc and LAN is not possible in this case.
Hence wireless transmission is must and it will be usp of my project.
After discussing with my project guide i sorted out the problem.
Now the position of tx and rx are slightly changed.
THe distance between tx and rx is around 100 to 120 meters but the physical location remains same i.e. rx on second floor and tx on ground floor.
I think now transmission might become easy than prev case.
Stil i don't know how to implement it.Will u plz tell me how the zigbee transmission is complex.

[ Edited Thu Aug 21 2008, 12:06AM ]

Arun Kumar V

Thu Aug 21 2008, 07:42AM

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Hello vaibhav,

RS232 can be used with help of 433Mhz RF modules ( range 300 meters in open air) for longer range ( as in your case) you have to go for Hi-power Transceiver ( 1Km range)

the above excerpts are from my previous post, here's the Hi-Power long range(up to 1Km) 433Mhz Transceiver: