Multiple RFID Shields on Etherten

The RFID Lock Shield makes it easy to control an electric door strike using an Arduino and an RFID reader. (Note: obsolete, replaced by the RFID Door Lock Shield). [Product page]
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thebeast305
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Joined: Mon Apr 01, 2013 9:53 am

Multiple RFID Shields on Etherten

Post by thebeast305 » Mon Apr 01, 2013 9:56 am

Hi,

I'm new to arduino (and kinda new to electronics) and just have a quick question (hope it's not a stupid one)

Is it possible to stack multiple RFID shields onto a single Etherten (for multiple doors)?


Looking forward to any responses.

Thanks in advance.

cef
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Re: Multiple RFID Shields on Etherten

Post by cef » Mon Apr 01, 2013 10:11 am

Welcome to the world of Arduino! There are no stupid questions. :)

The current design of the RFID shield does not allow for multiple RFID readers or multiple relays for doors.

The shield uses specific pins for talking to the RFID reader and to control the door relay, that cannot be changed on the shield itself.

If you could change the pins, you could probably control two or three before you ran out of pins, however the software would need to be changed to suit.

Shields like some of the relay boards use an I2C bus to communicate to get around things like this. Unfortunately I2C hasn't been used on the RFID shield, otherwise it would most likely be fairly easy to change.

Note: Any change like this would require the code on the Arduino to change as well to support it.

thebeast305
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Joined: Mon Apr 01, 2013 9:53 am

Re: Multiple RFID Shields on Etherten

Post by thebeast305 » Mon Apr 01, 2013 10:30 am

cef wrote:Welcome to the world of Arduino! There are no stupid questions. :)

The current design of the RFID shield does not allow for multiple RFID readers or multiple relays for doors.

The shield uses specific pins for talking to the RFID reader and to control the door relay, that cannot be changed on the shield itself.

If you could change the pins, you could probably control two or three before you ran out of pins, however the software would need to be changed to suit.

Shields like some of the relay boards use an I2C bus to communicate to get around things like this. Unfortunately I2C hasn't been used on the RFID shield, otherwise it would most likely be fairly easy to change.

Note: Any change like this would require the code on the Arduino to change as well to support it.
Thanks cef!

I was worried that was going to be the answer. So essentially if I wanted to control multiple doors i'd just need to have multiple arduino's each with a RFID shield and then software to suit?

cef
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Re: Multiple RFID Shields on Etherten

Post by cef » Tue Apr 02, 2013 12:52 am

That's probably the easiest way.

You could make something up where you have only one reader but more than one relay (eg: you scan the RFID and it opens multiple locks via individual relays), but that's getting more complex, especially if you're new to Arduino. You most likely wouldn't use the shield for this setup (and instead use a 4 channel relay module or the 8 channel relay shield). This way you could have different RFID tags open different locks, rather than any listed tag always opening the same lock.

If you're interested in going down that route, I suggest you at least get hold of one of the RFID shields first, as this will give you a great introduction to Arduino and RFID, improve your electronics knowledge. You can then work from there to get the desired result.

The sketch (or code) for the Arduino to run the RFID shield is listed on the product page (it's the example sketch from the Practical Arduino book), but can also be found on Github at: https://github.com/practicalarduino/RFI ... trolSingle

thebeast305
Posts: 3
Joined: Mon Apr 01, 2013 9:53 am

Re: Multiple RFID Shields on Etherten

Post by thebeast305 » Tue Apr 02, 2013 5:17 am

cef wrote:That's probably the easiest way.

You could make something up where you have only one reader but more than one relay (eg: you scan the RFID and it opens multiple locks via individual relays), but that's getting more complex, especially if you're new to Arduino. You most likely wouldn't use the shield for this setup (and instead use a 4 channel relay module or the 8 channel relay shield). This way you could have different RFID tags open different locks, rather than any listed tag always opening the same lock.

If you're interested in going down that route, I suggest you at least get hold of one of the RFID shields first, as this will give you a great introduction to Arduino and RFID, improve your electronics knowledge. You can then work from there to get the desired result.

The sketch (or code) for the Arduino to run the RFID shield is listed on the product page (it's the example sketch from the Practical Arduino book), but can also be found on Github at: https://github.com/practicalarduino/RFI ... trolSingle
Yeah, although having a few door strikes hooked up to relays and controlled from 1 rfid reader and different tags for different locks would probably defeat what I'm trying to achieve (a multi-door rfid access control system for my house) But i see what you mean.

I think I might buy an arduino and lock shield and play with it. I've hooked up plenty of alarms, access control systems and other gear in the past just never made any from scratch, I've always bought pre-made systems and just wired them in. Ideally I want one central unit (be it andruino, pic, raspberry pi, whatever) that has all of the details in it then to just link all of the rfid readers and strikes into that (so that it's all centrally managed) and power it all over ethernet but there's no way i'm buying an etherten + a door strike + rfid lock shield + rfid reader module for each and every door lol it'll end up costing $150+ a door and I'm sure there's a better way to do it. Anyway enough of my ramblings haha

Thanks for your help cef.

cef
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Re: Multiple RFID Shields on Etherten

Post by cef » Tue Apr 02, 2013 8:33 pm

Main issue with this sort of thing (decentralised readers) is the length of cable between the RFID reader and the host processor. You can usually drive a strike from some distance, but the RFID reader definitely has a limit on how far it can be from the host (it's serial comms @ 5V).

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