Member Discussion

Wiegand Card Reader Cable Specification?

I am having a discussion at the office regarding the requirements for Wiegand Data Card Reader cable.

Does Wiegand Data require non twisted pair cable or is that just the minimum requirement? Is twisted pair cable detrimental to the data signal?

Please provide supporting documentation as I am noticing different manufacturers say different things. Maybe HID would like to comment?

HID's recommended cable for the old Prox line is Alpha 1295C, which is a 5 conductor 22 AWG, untwisted, overall shield. The cable I used to use more than any was West Penn 253186B, which is 18/6 untwisted, overall shield. We sometimes used the 22/6 version of that, rarely, if runs were short.

I'm not sure if twists are detrimental, having never tried it. I imagine if they were it would depend upon which pairs were twisted.

I am aware of HID spec of 5C untwisted cable. What I am trying to understand is it a requirement or a minimum spec.

If you look at manufactures of composite access control cable such as Belden, General Cable, Superior Essex, and others manufactures usually they make the card reader cable with twisted pairs. Also several card access manufactures such as DSX, Kantech, and others recommend twisted pairs in their literature.

Twisted cat5e and cat6 are not good to be used for wiegand readers. The twist by the data can cause problems with the data packets. If you have to use cat5e or cat6, make sure to have the data running on two different twists. Usually the longer the run, the bigger chance of there being reader issues.

As a gerneal rule, wire that are deisgned for wiegand readers are the best to use. (such as Alpha 5388). These cables are usually, shielded, non twisted multicore cables.

Do you have any documentation to site to back up your claim? Why are all the manufatures I liked to in my original post using sheidled twisted pair wiring? I understand that the HID reader spec a 5c wire but is that a minimum requirement? Wouldn't a twisted pair shielded be even better? Several manufactures also spec twister pair wiring and twisted pair shielded wiring.

Since the HID transceivers are apparently not using a differential signaling method, i.e. common mode rejection, use of twisted-par would be non-optimal at best.

Common mode rejection is the method that UTP uses to reduce noise. But unlike a shield, you need equipment on both ends to get the benefit. Plus the signals and their inverse must be put on the same pairs.

So without a shield, and due to the added crosstalk resulting from twisting non-inverted signals, IMHO, the performance would be worse than the specified cable.

If there were only 4 wires, I would say that you could use STP, Sheilded Twisted Pair, without incident, by assigning each pair to a single signal, but you have 5 and so would have to double one up...

Do you have a link showing that HID does not use differential sgnaling mothods?

I said 'apparently' using for a reason. The reason being you said:

I am aware of HID spec of 5C untwisted cable.

If the hardware is using differential signaling (more expensive), yet the cable spec demands untwisted cable, IMHO, that is strange...

Do you have an explanation for how this came to be?

I'll see what I can dig up and report back...

Do you have a link showing that HID does not use differential sgnaling methods?

To be exact, your initial post asked for the "requirements of Wiegand Card Data Reader cable", not HID, although you requested their comment.

The standard Wiegand wiring interface does not define any differential signaling. It's a 3 wire serial, running at 5V to achieve distance.

The Wiegand interface uses three wires, one of which is a common ground and two of which are data transmission wires usually called DATA0 and DATA1, alternately labeled "D0" and "D1" or "Data Low" and "Data High". When no data is being sent, both DATA0 and DATA1 are pulled up to the "high" voltage level — usually +5 VDC. When a 0 is sent the DATA0 wire is pulled to a low voltage while the DATA1 wire stays at a high voltage. When a 1 is sent the DATA1 wire is pulled to a low voltage while DATA0 stays at a high voltage. The high signaling level of 5 VDC is used to accommodate long cable runs from card readers to the associated access control panel, typically located in a secure closet. Most card reader manufacturers publish a maximum cable run of 500 feet. An advantage of the Wiegand signaling format is that it allows very long cable runs, far longer than other interface standards of its day allowed.

Perhaps HID can use differential signaling, but only between its own equipment, when auto-detected? I am still looking for confirmation of that.

But I stand by my statement that running a common ground, non-differential signal, such as standard Wiegand, on UTP will underperform that of a shielded cable.

Going back to my original question I am trying to compare twisted pair wiring to non twisted. I don’t want to compare the shielding. So would having a twisted pair wiring be detrimental to the signal compared to a non twisted pair wiring if they were to both shielded?

I completely agree with you that twisted pair wiring would under preform compared to a shielded non twisted pair wiring.

I am trying to find the referece documents from the manufactureres that I deal with. But I know they all say to stay away from twisted.

Going back to my original answer of

If there were only 4 wires, I would say that you could use STP, Sheilded Twisted Pair, without incident, by assigning each pair to a single signal, but you have 5 and so would have to double one up...

I would say if the cable needs nothing besides the 3 wires (two signals and shared ground), then using STP and by putting each signal on their own pair as well as the ground should perform well. It also halves the resistance of the conductors. Note that this is not using any differential signaling, and the effect of the twisted pairs are effectively eliminated by putting the same signal on both wires.

If you want to use balanced/differential signaling and twisted pair there are ways to do that with rs-485 adapters.

This is unfortunately opinion, though it is well considered, so I think I would like to see what HID says as well...

If you look at the composite cables form my original post all the card reader cables are twisted pair shielded cables. These cables are from reputable manufactures so if they are selling shielded twisted pair cabling for card readers is everyone telling me they don’t know what they are doing? Does anyone have actual backup to prove twisted pair cabling is detrimental? I am not interested in opinions as I have enough of those around the shop.

Quote from HID which I found interesting.

"Do iCLASS Revision C readers still require shielded cabling?

No. HID’s new innovations in RFID reader development significantly reduce installation costs by no longer requiring shielded cable to run between the reader and controller. All wire pigtails exiting the reader no longer contain a shield wire. This new enhancement does not affect data- run length maximums. Utilize twisted pair cabling for maximum noise immunity."

While I cant say for sure re HID. 3 manufacturers that I am certified with all insisit that you dont use twisted cables. As a matter of fact, one of them, wont even work on trouble shooting reader issues if you use cat5

I'd be interested in this as well - I'm spec'd to wire a site for HID readers (I believe mostly MiniProx and maybe a few ProProx keypads) and they have me using Cat5e, would be good to know before we start if I have to have them change the cable spec.

Just a couple of thoughts here. Wiegand was invented some 50 years ago before Cat 5 etc. I think you will find that each manufacturer uses their own wiring specification, and most if not all have settled over the years on the accepted "wiegand" standard, 6 conductor non-twisted, overall shield.

CAT 5 or 6 is designed to extend the ability of the cable to transmit data using tighter winding, the winding canceling out interference. The issue is the power. You will drop too much voltage using 24ga wire to properly power your readers.

I would consult the manufacturers documentation or tech support before using CAT anything. We have tried it in elevators and it did not work well at all. We had to use a Wiegand extender down to the elevator car and standard 6 conductor with an overall shield.