View Full Version : Hello all!

03-06-2013, 06:32 PM
Hello everyone, I'm Jon. We are in the advanced planning stages of our shop called Imagine.Design.Build.
I have been tossing the idea around of a controlled access system. I'd like to take it a step further than a simple rfid system allowing access to a few doors. I'd like to have the ability to control access to all of the dangerous machines in the shop. I especially would like to be able to lock certain people out that have not been trained on the equipment. I see the rfid equipment on this site are read only, this would limit the ability to change access with the same card. Will the Arduino Read/Write modules commonly found on eBay be compatible with the wireless modules here? Please be kind, I'm new to this type of project. Thanks in advance! -Jon

03-06-2013, 06:51 PM
Tech Shop has tried a system like this in their San Francisco and San Jose locations.

They do not store information on the cards, though; instead, each reader is connected to a central database, where all your equipment clearance is stored.

You should know that a "maker space" will probably be full of people who would like nothing better than develop a reader/writer that updates their card to have all the access allowed. (Just like a certain university ended up giving CS students free lunch for a while before they realized that cards with stored value are easy to fake...)

03-06-2013, 07:01 PM
Our insurance company likes the idea. They also like the idea of a binder telling you not to shove your hand in the table saw. So I'm just trying to explore all options. Thanks for the reply.

03-06-2013, 07:18 PM
Thoughts on optical fingerprint sensors for this application? Like I said, trying to explore any and all avenues.

03-06-2013, 09:31 PM
If your maker space has a machine shop, machining gives you small cuts on your fingers all the time. That might mess with finger print sensors :-) And finger print sensors need to be networked just like read-only RFID cards. I actually think RFID cards are a fine solution for this application. That, or retina scanners ;-)

03-06-2013, 10:02 PM
Yeah, the more I thought about the fingerprint scanner, the more I didn't want to make sure they were kept clean:p

03-07-2013, 06:05 AM
They use full-hand scanners here to control access to housing and dining halls. You either swipe or type your ID number (all the card has is ID number) and stick your hand in a small-ish box. Basically, there are four little metal posts (for the webbing between fingers) to keep all hands in a uniform pose. On the bottom surface is a reflector and in the top is a camera (and likely IR LEDs). Since the position of the hand is mostly the same in all scans (because of the posts), it is simply a matter of comparing the image taken with the calibration images stored in the central database (pointed to by the ID number). Seems to work well enough as I don't recall anyone cheating the system, and the reflectors get pretty grimy looking after a couple years of use, but seem to keep working adequately. Pretty sure the four little posts also sense the presence of skin (capacitance or galvanic response) to make sure the hand is fully inserted/positioned.

I was going to save #666 for a vanity post making fun of bible-thumpers, but I couldn't think of many ideas that probably wouldn't get me banned.

03-07-2013, 10:54 AM
Regarding the table saw specifically, I don't see any reason not to use a Saw Stop these days.

03-08-2013, 08:54 AM
Yeah, we are looking into getting a SawStop. They are quite spent though. We will have to see. Back to the RFID. If the software dictated who got entry, and not info on the card (just numbers) that would limit the "hack" issue correct?

03-08-2013, 09:08 AM
Back to the RFID. If the software dictated who got entry, and not info on the card (just numbers) that would limit the "hack" issue correct?
Not really unless you used some sort of extra method of identity verification that cannot be duplicated electronically (can replicate rfids and magstripes without much difficulty given the right tools and a little determination). That is a variation of the problem jwatte mentioned with the cs students (find someone with access and copy their swipecard). Even a simple PIN would make it a bit more secure, as long as people don't share their PIN.

03-08-2013, 09:47 AM
Ahh. I see what you are saying. I don't really see it being too much of a problem. We will train everybody who uses the space anyways so they won't really be gaining anything by copying a card. It's mainly a "insurance"safety feature. They like to see systems in place.

Now. What products do I need to order to start messing around with it? I want RFID, but I want it to wirelessly communicate with a remote computer ( at front desk), but under 100 ft away. I will need relays I'm assuming, to turn power on to the machines. Can you guys point me the right direction? Sorry for the noob questions. You guys have been very helpful and polite:)

03-08-2013, 12:07 PM
For wireless communication, a small single-board computer like a Raspberry Pi with a WiFi USB plug-in would probably be best. You can get RFID readers that speak serial UART, and hook that to the RPi. Just make sure the voltage is the same -- Raspberry Pi I/O is 3.3V and it dies if you try to hook 5V I/O to it. There are Arduinos and Arduino WiFi Shields that accomplish the same thing, but actually cost more for less capabilities.
However, I would recommend actually running wired Ethernet. (The RPi comes with that on board already, so no extra dongle needed)

03-08-2013, 12:29 PM
Gah, jwatte beat me to the punch. His method would work pretty well if you can get your hands on enough RPi and cheap wifi dongles and logic-level converters.

Well, trossen used to sell a really cool little device called the RedBee (even had a nice plastic enclosure for mounting on surfaces), but that appears to have been replaced by the RFIDuino shield (125kHz EM4102). If you want to go super cheap, you could go with the seeedstudio 125kHz (EM4102) readers (I have one of the plain UART versions along with a collection of their dongles/cards and they work well enough). Just about any way you decide, you will have to make an enclosure to protect it, but that should be easy enough for your group to do (Cytron makes a fully sealed reader, but no immediately available documentation).

Whatever your choice, connect the reader to an arduino or other minimalist microcontroller system and an Xbee (they're easy to use, but there are plenty of other choices). You won't need a high baud rate, so even indoors you should get pretty good range out of them (max 300ft line of sight). Use the arduino to pass the output from the RFID reader over Xbee to the central database (some form of packetization and/or encryption might be nice). If the RFID tag is cleared to use that machine, send a message back to the arduino over Xbee to tell it that it is okay to power the machine. Controlling power to the machinery is a bit of an open question. It depends a lot on the voltage and current ratings of the devices (solid state relays are nice, but expensive for really high power).

03-08-2013, 02:25 PM
You guys are awesome! That was very helpful! I'm sure ill have more questions after I receive all the toys. In the mean time, I'll continue reading up here! Thanks again!