M1 KP2 Wiegand Interface Problem

I have a fingerprint/prox card reader I purchased through a local supplier, that works great with the Elk M1KP.  I've been using this reader for over 2 months with the ElkM1 for access control.  It has not missed one valid fingerprint access or card access.  However, I'm having problems getting this fingerprint reader to work with the KP2.  No matter what I try, the KP2 acts as if there is no signal coming from the print/prox reader.  The only response I get that indicates anything is happening is if I remove the D0-D1 connector from the KP2 and reconnect.  I get one short beep from the KP2, but nothing shows on the display.
 
With the KP, I just connected the V+, GND, D0 and D1 wires to the corresponding inputs of the print/prox reader, and saved the reader output codes for fingerprints or prox card activations as different users' access codes in the Elk system.  I was then able to program Elk rules to perform various functions based on whose fingerprint or card was presented.  Since there are only 2 Wiegand connectors for the KP2, I connected the D0 and D1 outputs of the reader to the corresponding connector on the KP2.  I connected V+ and GND to the red and black input wires of the KP2.  Unless I'm missing something, that would be the proper connections.  I tried reversing D0 D1 just to check, but still no dice.
 
I contacted the supplier of the KP2 who contacted Elk, but they could offer no suggestions, other than it should work and to try a replacement KP2.  I've now done that, but nothing has changed.  I tried to call Elk myself, but since I'm a homeowner rather than a professional installer, they don't want to talk to me.
 
I've seen a few members of this forum have experience with 3rd party Wiegand-compatible devices, and would really appreciate and suggestions you might offer.  I can continue using the Elk KP, but wanted to take advantage of the KP2's sleek look.
 
Thank you,
Jerry

Check voltage? Many weigand readers are very sensitive to getting voltages below 12V.
 
The beep only indicates whether or not the reader is getting power.
 
Maybe a pinout change or incorrect plug locaton? Since the issue doesn't follow the KP, the issue is between the reader and KP2, assuming you have a KP2 with functionining weigand input.

Thanks for the reply, DELInstallations.  I'll check the voltage at the reader when I get back home.  I don't know if voltage is the problem, though, since the reader continues to make all of its normal beeps, noises and LED indications (accept/reject/onboard relay closure, etc.) regardless of which keypad it's connected to.  But, at this point, I'll try anything.
 
I'm not sure what you mean by "pinout change or incorrect plug locaton".  The only difference I can see between the KP and the KP2 is that there are only connections for D0 and D1 on the KP2, as opposed to a complete power/data connection for the KP.  However, the reader functions with only 4 connections with the KP, power +/- and data 0/1.  I have those same connections with the KP2, I just draw the power from the bus wiring when using the KP2 rather than from a dedicated wiegand connector, as with the KP.
 
I had hoped that I could rule out the possiblility of a non-functioning wiegand input by exchanging the first KP2 for a new one, and I'm sure that's why Elk recommended to the vendor that we go that route. 
 
I have noticed the the D0/D1 connector on the KP2 has pins that are considerably smaller than those on the KP.  Since it's just the data signals on these pins with the KP2, I wouldn't think size really matters.  However, I initally had a problem with undersized wiring between the reader and the KP, mimicking the problem I'm having now (reader working but wiegand signals not being received by Elk during user programming).  It's only a short wiring run (about 18"), but I replaced the stranded wiring I was using with 24ga. solid wiring and everything worked well.  Nothing I can do about the size of the KP2 connector pins, but I thought I'd mention it.
 
Thanks,
Jerry

nitewind said:

 However, I initally had a problem with undersized wiring between the reader and the KP, mimicking the problem I'm having now (reader working but wiegand signals not being received by Elk during user programming).  It's only a short wiring run (about 18"), but I replaced the stranded wiring I was using with 24ga. solid wiring and everything worked well.

Click to expand...

 
The size of the wire and stranded vs solid really shouldn't matter for this.  I'll guess that you're using a different cable to connect the reader to the KP vs the KP2, correct?  If so, that suggests that the problem is in the wire/cable and not the reader or the KP2

RAL said:

The size of the wire and stranded vs solid really shouldn't matter for this.  I'll guess that you're using a different cable to connect the reader to the KP vs the KP2, correct?  If so, that suggests that the problem is in the wire/cable and not the reader or the KP2

Click to expand...

 
Actually, I got tired of connecting and disconnecting the 2 different wiring harnesses when switching out the KP and KP2.  When I reinstalled the KP yesterday after trying the replacement KP2, I left the power leads to the reader connected to the V+ and GND wiring on the data bus, and just slid the 2 individual D0 / D1 connectors I was using with the KP2 onto the D0 and D1 pins of the KP.  It will make it a lot easier to switch out keyboards when I again test the KP2, but also rules out any wiring differences causing the problems. 
 
The reader and KP combination are working fine using the KP2 wiring arrangement.  Same wires and connectors, just different pins for the data.

RAL said:

The size of the wire and stranded vs solid really shouldn't matter for this.

Click to expand...

 
I also thought it odd that I was originally unable to get the KP to receive wiegand signals from the reader using CAT5e 24ga. stranded wire.  However, when I replaced the CAT5e with the 24ga solid conductor cable, I've had no problem since.  I really didn't think it would take such substantial conductors to pass a data signal.  Power...that's understandable, but not for signal purposes.

nitewind said:

I also thought it odd that I was originally unable to get the KP to receive wiegand signals from the reader using CAT5e 24ga. stranded wire.  However, when I replaced the CAT5e with the 24ga solid conductor cable, I've had no problem since.  I really didn't think it would take such substantial conductors to pass a data signal.  Power...that's understandable, but not for signal purposes.

Click to expand...

 
That's correct - the data signals are very low power in an application like this.  You could use 30 gauge wire over the short distance you have here and it would be fine.   Not sure what made the difference when you switched to solid wire.  Are you using insulation displacement connectors on the end of the wire?  There are differences in connectors meant for solid wire vs stranded wire, and that could be what made the difference.
 
It's possible that whatever connector you are using isn't designed for use with the short pins that the KP2 has, and a different connector is required to make proper contact.

For testing, I used the connectors from a motherboard-to-front panel connector (the black slip on connectors for HDD, Reset, Power, etc.).  I removed the crimped copper connector/wire combination from the black plastic housing.  The connector is a small copper conductor that wraps around the pin on all 4 sides.  It has a split on one side of the conductor that allows it to fit slightly different sized pins, so it fits both the KP and the KP2 D0 and D1 pins snugly. A continuity check from the bottom of the D0 and D1 pins on the KP2 with these connectors attached at the upper portion of the short pins, to the other end of the attached wires shows continuity (not an easy task considering how short the KP2 wiegand pins are!). Again, these same connectors on the KP wiegand pins work great.  Attached to the KP2...nothing. 
 
It's almost as if there is a toggle, keypad or system setting that needs to be activated in order to get wiegand to work with the KP2, but I've found no such setting.

DELInstallations said:

Check voltage? Many weigand readers are very sensitive to getting voltages below 12V.

Click to expand...

 
Checked the voltage at KP2 input, 13.6V, same at reader input.  Checked voltage at each of D0 and D1, 4.4V to ground each.

It's been a while since I've done this - I do remember some tech-notes stating that wire length from the keypad to the reader was pretty important - not sure how long the run is... but I can confirm that there's nothing to set; I have a wireless fingerprint reader hooked into mine and I did the same basic thing - I tapped into the bus power and used a spare PC header connector to slip on those pins.
 
If you have a DBH I'd take the reader and keypad to the closet and test there to see if things are any different.

nitewind said:

A continuity check from the bottom of the D0 and D1 pins on the KP2 with these connectors attached at the upper portion of the short pins, to the other end of the attached wires shows continuity (not an easy task considering how short the KP2 wiegand pins are!). Again, these same connectors on the KP wiegand pins work great.  Attached to the KP2...nothing. 

Click to expand...

 
It sounds like you've done all the reasonable things to get to the bottom of this, so now I'm pretty well stumped, too.

10' max wiegand length off KPAM or KP.
 
Weigand data shouldn't make a difference if it's C5 or other cable construction. Actually the twists are more benefitial as most access control reader cable is twisted pair and shielded.

Your D1 and D0 should read different voltages in relation to ground, one is clock and the other is data signal, completely different items. Reading the same voltages indicates there's no data going downstream.

The length of my wires to the reader is 18-24 inches.  I did have a problem using CAT5 for V+, GND, D0 and D1, but replaced with some 24ga. sollid coper wires, and all worked well with the M1KP.
 
The D0 and D1 voltage I was referring to is when the reader is idle.  I've Googled other Wiegand-compatible interfaces, and all the specs I've seen for guaranteed minimum voltage level on a data output, set to 1, is 5V.  I've been unable to find a Wiegand spec for minimum voltage level of a "high" digital output (ie: 4.6V, 4.4V, 4.0V...).  However, 4.4V at 2 digital output terminals for a device that is guaranteed a minimum of 5V by other manufacturers seems a bit low.  Maybe someone who is familiar with Wiegand specs can tell me if 4.4V is too low to signal a change when the voltage drops to 0V during data transmission.  I've contacted tech support for my print/prox reader to see if this "normal" or "high" state voltage of D0/D1 is too low.
 
I'm really not sure what else I can do.  The reader works great with an older Elk keypad.  That makes it difficult to tell the reader vendor that it's a problem with their equipment.  I have exchanged the M1KP2, with the same results, so that makes it difficult to tell the KP2 vendor that it's a problem with their equipment.  Hopefully, a positive result with another W26 device and the KP2 will shed some light on whether it's a problem of signal strength on the reader.

Any other reader to try on the KP2?

nitewind said:

The length of my wires to the reader is 18-24 inches.  I did have a problem using CAT5 for V+, GND, D0 and D1, but replaced with some 24ga. sollid coper wires, and all worked well with the M1KP.
 
The D0 and D1 voltage I was referring to is when the reader is idle.  I've Googled other Wiegand-compatible interfaces, and all the specs I've seen for guaranteed minimum voltage level on a data output, set to 1, is 5V.  I've been unable to find a Wiegand spec for minimum voltage level of a "high" digital output (ie: 4.6V, 4.4V, 4.0V...).  However, 4.4V at 2 digital output terminals for a device that is guaranteed a minimum of 5V by other manufacturers seems a bit low.  Maybe someone who is familiar with Wiegand specs can tell me if 4.4V is too low to signal a change when the voltage drops to 0V during data transmission.  I've contacted tech support for my print/prox reader to see if this "normal" or "high" state voltage of D0/D1 is too low.
 
I'm really not sure what else I can do.  The reader works great with an older Elk keypad.  That makes it difficult to tell the reader vendor that it's a problem with their equipment.  I have exchanged the M1KP2, with the same results, so that makes it difficult to tell the KP2 vendor that it's a problem with their equipment.  Hopefully, a positive result with another W26 device and the KP2 will shed some light on whether it's a problem of signal strength on the reader.

Click to expand...

 
The Wiegand interface dates back to the 1980s and is based on 5V TTL logic levels.  5V is the logic supply voltage, but the signal levels usually are below that.  Typically, the input circuits will see anything above about 2.5V as a high input level.  If you are measuring 4.4V, that should be fine.
 
It may seem like a long shot, but if you obtained the second KP2 from the same supplier, it's possible that they came from the same manufacturing lot and both could be bad.  It wouldn't be the first time.