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RF proximity switching

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rjh

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Hi all,

I'm new and not any form of electrical engineer. I've got a small project in mind and I'm wondering what it would take - or indeed if anything like it actually exists.

I would like to control flow of electricity to a device (an appliance) by inserting (or otherwise) a programmed RF tag (or other very-near proximity control method). Scenario: I want to give permission to only certain people to use said device - Person A is authorised so if they insert their personal tag containing the relevant credentials the electricity will flow and they can use the device; Person B is not authorised and their tag does not have the relevant credentials therefore electricity does not flow.

I realise that some of this scenario requires other technology (i.e. software) to run - checking credentials against a database etc.

However is it possible to have a unit that controls flow of electricity in response to user credentials? Happy to hear any and all ideas, I'm not glued to any one approach.

Cheers,

rjh
 
Think of your application as the same thing as using an ID card to unlock a door electrically. The expensive, off the shelf way is to go to a security company with access control products (Identiv, etc.). They have the database software, cards, readers, etc. The software will be WAY WAY WAY more complex than you need for your simple task, but you need something to create users, assign rights and credentials, link those credentials to the serial numbers of the RFID tags, key cards, etc., interface with the key reader, and drive an output relay. From your question I assume that you want your users to have a physical key device rather than remember an access code, but the electronic key approach is much more expensive than a keypad and an Arduino.

ak
 
This is an ideal candidate for an arduino and a rc522 module or similar, google them and see if you can make sense, all of the coding has allready been done, if yor handy shouldnt be too hard.

And yes welcome here.
 
Why does it need to be so complicated?

How about 10 switches in series. A random number or N.O. and N.C. switches. Certain switches need to be ON and certain switches need to be OFF for electricity to flow. The person that knows the correct combination can make it work.
 
My Circuit offers a Greater Security.

Every Time you push a Wrong Number, It Resets.
 
My guess is that the OP wants a physical key rather than have users remembering a code.

ak
 
Chem's circuit is more secure and quite elegant.

You could and I've seen this done wire 4 or more 12 position rotary switches in series, then only when all 4 switches are in the correct position will you get an output to unlock, no electronics require at all.
 
My Circuit offers a Greater Security.

Every Time you push a Wrong Number, It Resets.

But what makes that better? My circuit offers great security too. Put 1000 N.C. and N.O. random switches in series it never works until you get the number combination correct like a bank vault. Possibilities are 1000 x 1000 x 2 = 2,000,000. possible combinations.
 
But what makes that better? My circuit offers great security too. Put 1000 N.C. and N.O. random switches in series it never works until you get the number combination correct like a bank vault. Possibilities are 1000 x 1000 x 2 = 2,000,000. possible combinations.

1000 Switches? Definately BIG and EXPENSIVE!

My Circuit: If Someone just stands there and just pushes buttons, every time he hits a wrong number, it resets to start over.
But he will never know he hit a wrong number.

Even though the combination is only 4 Buttons, This Dramatically increase the Odds against him.
And there can be as many RESET buttons or Touch Pads as you want.

I am not sure How you would Calculate the ODD's on this, but I can guarantee it is Very HIGH.
 
Bit of a guess here chem but I'd say your system has 630 : 1 combinations.

I'd sooner enter a code on 10 pushswitches than a 1000 toggles.
 
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Wasnt meant to be an argument chem, maybe your right.

My reasoning is:

Standard keypad with 4 numbers from 0-10 has a possible 10 x 10 x 10 x 10 combinations = 10,000 total.

Your system has 10 keys, however from the schem you cant repeat the same number twice, so
possible combinations = (10 x 10) x (10 - 1) x (10 - 2) x (10 - 3), or 10 x 9 x 8 x 7 = 5040 possible combinations.
Also you could put the number in the system any way round, such as 1234, 4321 both would work,
there are 8 ways of entering in a 4 digit number, so 5040/8 = 630.
I might be wrong there, thats just a bit of reasoning I find such things interesting.
 
No the Lock will NOT Open if the numbers are Reversed or Switched around.
They MUST go in ONE Order Only as set for.


If Any Wrong number Pressed, You must START OVER!

So Partly is the question is:
What are the ODDS of getting the 4 Digits Correct, Without hitting a Wrong Number.
And with a Key Pad you also have the " * & # " to use for Entry or Reset.
 
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Back in the days when I worked every morning I walked up to a gate and presented my RFID badge. The gate opened and allowed entry and all day I used my badge and assorted codes to transgress certain areas. Don't see a need for something that elaborate. If this is a case of some employees can access the machine and some can't a simple bar code reader could scan badges or whatever. Bar code reader could easily interface with an Arduino or similar uC. There is no shortage of ways to go about doing this, just a matter of how complex the user wants things to be? Have employees with access use a code? Just be damn sure the code isn't shared. Really? How secure do you want it?

Ron
 
I'm going to use this **broken link removed** site as an example of not necessarily what you want to do, but it introduces a technology. The technology is the iButton. Unfortunately, this lock only accepts one user.

The ibutton is basically a 2 wire (commonly called 1-wire because they don't include ground) which is programmed with a unique serial number. I THINK it's like 128 bits/
So, yea you need some sort of database management and security and in this case, a way to supply power when the batteries get depleated.

It does require physical contact.

So, the trick is in all cases is a database for who has access and it falls under the category of an "access control system".

So, here's a simple scenareo:

Many user keys
A key that puts th lock out of service
A key that puts the lock in service
An Add key
A delete key
A programming key

Lets say some lights, externally powered for now and lets say it's a washer.
If the washer is broken, you can take it out of service. when it's fixed, you can brig it back into service.

If you have to add a user, you use the add.user key and then read the next key. That user is added. The time/date of the new key is logged.
If you want to delete a user and you "have the key" you use the "delete key".

We have not used the "programming key yet". What that might do is give you access say via USB, Ethernet, WIFI or whatever. The "port" could be visible, but not connected during normal use.

When you add a key, the time stamps are available, so you can associate a user with the key. You do that association with a PC connected to the lock. USB serial port or even HTML. A lot depends on how many users. A 1000 users requires something diffferent.

Access restrictions would be set up..

You would also have the ability to reove a user when you didn't have the key returned. You could read keys.

I was involved with an early RFID based lock system. A credit card PCB with antennas on them and a small active electronics that fit in a milled recess covered with plastic on both sides. It would activate early store anti-theft systems. There was a door controller that handled multiple doors with a coax and lock strike power to the door.
At the "secure location" a printer, terminal, controller and dual cassette tape were located. Every access printed on the terminal and access rules were entered on the terminal and stored on the cassette tape. The system could be set to fail-safe or fail-secure. In the fail-safe mode any card would allow access. The cards had a pre-printed code on them, so if they were lost they could be associated with the user.

You didn;t have to take the card out of your wallet. You just had to wave it (wave you wallet) across where the hidden receiver was or back your butt onto it.

The iButton technology is use din reverse, for guard walk-arounds. The buttons are placed in the locations where the guard has to do his rounds.

Then you have magnetic stripe cards and the old master key type systems.
 
Aha yes, your clocking the bits through a shift register from d type flip flops, so we are back to 5040 : 1 then, it'd take someone a long time to get that right.
Just goes to show you dont allways need an arduino.

4, 12 pole rotary switches would give about 2000, thats difficult to work out as you could set the first 3 switches and just sweep the last one every time, anyway its less secure.

If anyones interested heres a 3 switch lock:

http://www.next.gr/security/lock-circuits/Three-dial-combination-lock-l12012.html
 
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Still waiting on the OP to weigh in on a physical pass device vs. a keypad code.

LSI makes the LS7220 that performs the same function as the circuit in post #2, with added security. With the 7220, if a correct key is pressed out of sequence, the circuit resets. The circuit in post #2 does not. LSI also makes parts that are code-programmable through the keypad.

ak
 
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