# wiegand protocol

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#### Rob Kuipers

Hello!!!

I´m trying to conect a wiegand proximity sensor to a PLC or PC, but I cannot find information about the wiegand protocol.

¿ Does anybody knows where can i find information so I can make an adaptor for a PC or PLC?

Thanks!

[email protected]

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#### Carl Ramer

I missed the original posting for this thread, but thanks to Bob Lockert I can sort of deduce the gist of the matter.

Access control is one half of the wonderful world of electronic security for facilities, intrusion detection is the other half. Electronic
Security Systems (ESS) are a whole separate industry with publications, organizations and other features similar to Industrial Automation.

A quest for interleaving IA systems with ESS generally involves a little kluge work since neither industry follows the other's protocol very closely. If you're trying to control access at a remote location, the choices are basically two, local database and central database. Obviously local database is much less expensive and designed for smaller populations. Central systems are meant for populations in the
hundreds to tens of thousands. There are several local control units on the market in the $200-300 price range that can provide access control for a facility using a variety of credential technologies. Magnetic stripe, Wiegand wire, proximity and simple keypad are the most common. Features common to most good "Premise Control Units" would be upload/download via phone line, autodial to user specified number or numbers on alarm or condition, 600 event logging (or more), self power supervision and notification, 8 to 256 intrusion detection points for door sensors or other! types of devices (usually closed loop with EOL resistors for loop supervision), battery back up, support for multiple keypads, relay output on alarm/event, local and remote audio-visual alarms, etc., etc. Most are fully programmable. Any of the PCU's can take care of your access control/intrusion detection requirements and also provide at least a contact closure to a PLC if required. If anyone needs more specific information, contact me directly at [email protected] > > <<...OLE_Obj...>> > Carl Ramer, Engineer > Controls & Protective Systems Design > Space Gateway Support, Inc. > Kennedy Space Center, Florida B #### Bob Lockert Carl, Most of the facilities I deal with already have intrusion, temp, etc. detection at the PLC without the need for any PCU as you describe. Where access control via card or whatever is required, a separate local system is used. But the two systems don't talk to each other. It's not really necessary that they do so, but ideally they share a communications link back to a central site. This is most easily done by having the card number, intrusion point, key code or whatever; fed into the PLC. That data is then available at the central site through the PLC's native protocol. (Note: I recognize the security issues related to loss of communications and the benefit of redundant paths. But loss of communications is already detected at the central site and constitutes a priority alarm on its own.) Security devices and PCU's can be supplied with RS232 interfaces at greater cost, but spare serial ports on PLC's are often at a premium. On the other hand, a few additional digital I/O points can usually be found. What I would like to see is a DIN rail mounted module that provided a FIFO serial buffer of the weigand output of a reader. Field selectable jumpers for bit stream length and an output clock rate selection to accomodate the relatively slow scan times of the PLC. Alternately, the PLC could use a digital output to signal 'next bit' or something. The PLC can parse the serial data into appropriate fields and report the event to the central site. The goal is simply to differentiate between known and unidentified entrants without duplicating the entire communications network. Regards, Bob Lockert G #### Geoff Moore > Access control is one half of the wonderful world of electronic > security for facilities, intrusion detection is the other half. > Electronic Security Systems (ESS) are a whole separate industry with > publications, organizations and other features similar to Industrial > Automation. It's a little bit of an over simplification to divide the whole security industry into access control and intruder detection > A quest for interleaving IA systems with ESS generally involves a > little kluge work since neither industry follows the other's protocol > very closely. Hmmmm...so when an automation engineer connects two dissimilar systems it's called "integration" and when a security engineer connects two dissimilar systems it's called a "kluge"?? My company specialises in designing sub-components for integrated security and building management systems, and providing systems design and integration expertise. The security and IA worlds have a lot in common, for instance: - Lots of proprietory protocols - a few popular but non-interoperable protocols - a continuing quest for "the perfect interroperable protocol/comms media" that will never see an end because there are too many vested interests - the need to reliably gather information from distributed low cost sensors and do something useful with the information - etc etc etc This thread started off with a question about Wiegand. Never was there such an "accidental standard"!! As has been correctly stated it came from the ancient magnetic stripe reader where it was simply raw clocking and data pulses from the heads. It is now possible to find just about every type of identification technology imaginable on sale with a Wiegand interface. The original reason for this was to allow alternatives to magnetic stripe readers to be connected to old mag strip based system controllers. Unfortunately this "opportunistic solution" stuck. To refer to Wiegand as a "protocol" is really dressing it up in clothes it doesn't deserve. It is a physical layer interface definition, which offers a representation of information coded on som ID device or other. As a result there are many manufacturer specific variants. Most popular would be 26 and 34 bit types from the mag.stripe world, but with different sized facility codes, user types and user codes required for different applications that's way to limiting for most up to date applications. You really need to speak to the specific manufacturer to get details of the specific implementation you want to deal with. Wiegand is uni-directional (unless you implement some proprietory two way scheme) so in it's basic form you cannot even tell a reader to "open the door", you need to run in another pair of wires to power or control the lock. It is over-complex for the job required these days (the majority of readers of any type now include some intelligence and could easily implement a more practical interface). There are many many MANY access control systems out there, the market is almost as overcrowded as the intruder detection market, and yet there are still companies all over the world producing more and more variants of the same old thing. There are a lot of very good products that do their jobs very well and that are actually quite easy to integrate. I'd suggest anyone who's looking for a solution speaks to a professional and gets the right tool for the job. I certainly wouldn't be looking to implement the functions on a PLC, I simply don't understand why you'd want to. Access control is far more closely related to the MIS and HR ends of a business than the industrial control end. Echelon is being adopted quite widely now at the more sophisticated end of the market, but in systems that are aimed at the$200-\$300 market you can't really expect too much!!

What we're involved with is integrated security and building management where the various systems in a building (access control, door entry, intruder detection, fire detection, CCTV, guard tour, energy management, HVAC, lighting control etc etc) all work together. We make an infrastructural product that allows the different systems to be integrated quickly and easily with no "kluge".

Geoff Moore
====================================
Straight Forward Solutions Ltd
Naas, Co.Kildare, Ireland
Phone : +353 (0)45 892739
Fax : +353 (0)45 893880
Mobile : +353 (0)86 8179683
email : [email protected]

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#### Ramer-1, Carl

Geoff Moore wrote:

> It's a little bit of an over simplification to divide the whole
> security industry into access control and intruder detection
>

Well said Geoff, but you missed a bit in my posting. I said that access control and intrusion detection were halves of electronic security for facilities, not the whole security industry. And those security features are by no means a large portion of facility automation.

There are several major and quite a few other companies that produce full up facility automation solutions that include access control and intrusion detection almost as bonus features to their primary functionality. Kluging, integration or modification is generally only needed if someone insists on trying to make an existing control or automation system perform functions (like security) that it wasn't intended to perform. A modification to most systems will kill any warranty or tech support you may have, so the other two options are left. Integration is obviously the preferred choice, but a kluge ("something not designed as a whole but rather put together from available parts. The term if frequently used by engineers..." from http://pespmc1.vub.ac.be/ASC/Kluge.html) is sometimes the only available option. None of us want to do that, but at times are forced to by external circumstances or conditions.

Carl Ramer

...and after a while Carl said, "There are parts of our culture that stink with phoniness. But we can do some wonderful things too. "
-- As recounted by Murray Morgan in the book The Dam

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#### Bob Lockert

I've used both mag stripe and proximity card readers with PLC's. Integration is simple only if you use serial ports. The problem with talking to a professional from the access control side of things, is that just like you,
they don't understand why you'd want to implement the functions on a PLC.

While 'access control' may mean physical access to you, my purposes are to enable access to the functions of the process being controlled. For example, an HMI panel may have an elaborate menu structure to provide operators with various supervisory type functions. It may be desireable to let anyone see status or alarm items. Only more senior operators can change setpoints.

A proximity card reader adjacent to the panel could be used to identify the operator to the PLC, which in turn could vary the menu tree accordingly. Furthermore, if this PLC was a slave to a central site, the operator presence, and his actions could be logged for historic purposes.

Yes, an access control system could be made to do this. But why add a complete system just for identity purposes.

There are also circumstances in which PLC's are more suitable to limiting physical access than a security system. Combustible gasses, H2S and

There are endless opportunities to implement simple security devices into control strategies. The weigand format (yes not really protocol) is almost ideal. I just need the data stream a little slower.

Regards,

Bob Lockert

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#### Geoff Moore

> I've used both mag stripe and proximity card readers with PLC's.
> Integration
> is simple only if you use serial ports. The problem with talking to a
> professional from the access control side of things, is that just
> like you,
> they don't understand why you'd want to implement the functions on a PLC.
>

Well actually I think you've missed my point, and the arguments you've presented still don't convince me othewise.

> While 'access control' may mean physical access to you, my purposes are to

Not at all. Access control is about controlling access. We don't only use it to control locks and gates. If we did there probably wouldn't be much interest for me on this list!

You're talking about identification technology, we use that identification technology to control and measure access to both physical and virtual
areas/functions including HMIs.

> For example,
> an HMI panel may have an elaborate menu structure to provide
> operators with
> various supervisory type functions. It may be desireable to let anyone see
> status or alarm items. Only more senior operators can change setpoints.

...and this is why using application specific, dedicated hardware makes sense. Why re-invent the wheel? Good access control products provide you with sophisticated user profiling and time profiles etc etc.

You talk about "senior operators". Well the position within the heirarchy of a company is set by the HR department (or at least someone senior in the management structure). If they are senior enough to change specific setpoints then they are probably only senior enough to get into specific areas of the plant at certain times during their shift. Who sets the seniority of a member of staff and who sets the shift times? Not the automation engineer.

In any reasonable sized facility you are going to have an access control system anyway. Why duplicate the functionality? If your senior operator gets fired the HR guy might take him out of the main access control system but who's going to remove his access priveledges from the PLC based access control system and how long will it take?

...and what about day workers? They need access to areas and facilities for a fixed amount of time then they should be locked out of everything automatically. Easy if all access is controlled by the one system.

If you want to vary the way your plant works depending on who's in the area then connect the relay outputs from your access control system into digital inputs on PLCs and use them to interlock the functions you are setting up.

> Furthermore, if this PLC was a slave to a central site, the operator
> presence, and his actions could be logged for historic purposes.

...all included in most reasonable access control systems.

> Yes, an access control system could be made to do this. But why add a
> complete system just for identity purposes.

I think the question should go the other way. Why duplicate a system that already does the job (and probably better and with a higher degree of
sophistication and flexibility)?

>
> There are also circumstances in which PLC's are more suitable to limiting
> physical access than a security system. Combustible gasses, H2S and
> radiation levels come to mind.
>
> There are endless opportunities to implement simple security devices into
> control strategies. The weigand format (yes not really protocol) is almost
> ideal. I just need the data stream a little slower.

I'm always interested to see the different approaches and trends taken in different parts of the world to tackling similar problems.

We've used access control system to provide interlocks into PLCs in lots of situations including in factories to control access to machines, the idea is far from new to us, but it simply wouldn't occur to me to waste a lot of the customer's time and money re-inventing the wheel when I could buy in a guaranteed to work first time solution that did the job perfectly well and at very little cost.

If the access control systems available don't carry the certification you require for the environment you intend to use it in I'm sure it is simply because nobody ever asked the manufacturer for it.

Ask, and if there is a market (even a niche one), I'm sure product will appear.

Regards

Geoff Moore
====================================
Straight Forward Solutions Ltd