Z-Wave reception is pretty poor


(Scott) #1

I’m just getting my ST Hub and related kit, especially z-wave door sensors, set up. My house is (I think!) pretty tiny - the footprint is probably 20ft by 30ft.

At the moment, the ST hub is sitting on top of the couch and has a mostly unobstructed view of the kitchen and dining room.
I’m trying to set up z-wave door open/closed magnetic-reed switches and they work perfectly right up to the last six inches, and then they move into “no contact” mode, where the LED stays hard on. If I move them a foot back into the room and make/break the contact then they’re fine.

Both doors are very modern with (steel? aluminum?) surrounds so I wonder whether that’s what’s causing the issue and, more important, what the solution might be.


(Never Trust @bamarayne) #2

It may be the doors, not sure.

What I can tell you is my house’s footprint is significantly larger, 3600 sq ft or so and my hub is in my basement and talks fine with zwave devices on the other side of house on the 2nd floor.

A hardwired Zwave device near your doors may help the devices communicate effectively on the network.

Is the rest of your house construction metal?


(Never Trust @bamarayne) #3

Also, what contact sensors are you using?

If they are in a metal jam of a metal door, that’s a problem.


(Scott) #4

Thanks JH

The sensors are generic door open/close devices with reed switches. To be fair, in the open air, the magnets work at around a 2-3 inch distance.
Your footprint is, as you say, significantly larger so I’m thrown as to what the issue is.

One of the doors is a flush mount so I can’t see the surround being the issue.

I can take pics if that would help?

Thanks again
Scott


(Scott) #5

I think I need to move the Hub. At the moment, it is best placed to see the garage (which contains most of my expensive toys!) but moving it is probably the first step


(Never Trust @bamarayne) #6

Yes pictures will help.

Also what make and model are the contact sensors?


(Scott) #7

Thanks again, JH
I made a quick video which I hope will show the problem and the distances (small!) involved.

The units are Ecolink Door and Window Sensors and it’s a ST Hub version 2


(Never Trust @bamarayne) #8

Cool house!

It really seems like a radio interference problem.

  1. Bad Radio on the hub
  2. Bad Radio on the sensor if other sensors pass the test in the video
  3. Your house is a metal faraday cage
  4. You have another radio system interfering with the Zwave frequency (I don’t know what country you are in, etc)
  5. You may be able to aleviate by adding hardwired zwave devices to act as relays

The area the sensor seemed to work in appeared to have unobstructed line of sight, so not sure if your walls are metal or something…?

Calling in the big guns @JDRoberts

In any event that sensor shouldn’t have any issues talking to that hub under the correct conditions. Something is wrong here.


(Scott) #9

Cheers :slight_smile: we like it!

We’re in the UK but for the sake of accuracy (and possibly complaints) this is all US spec kit. The outer walls will be aluminum mesh, so I can see them possibly upsetting the radio waves. That said, aluminum should have zero carbon / ferrous impact, I’d have thought.

Any suggestions appreciated - I would certainly have thought that this house should fall well within the z-wave spec.


(Never Trust @bamarayne) #10

Is it possible the US Zwave frequency has some very bad interference in the UK from overlapping systems using that same frequency there?


#11

Excellent video.

I’m really tired, so this is going to sound grouchy, but I’m not grouchy I’m just tired.

It’s the range. And it’s the metal door. It’s not complicated. Those are inexpensive sensors and they just don’t have the power to handle what you’re asking them to do.

Normally when we lay out Zwave battery powered devices (not zwave plus), we assume about 12 m of range. I think you’ve clearly gone beyond that. And the metal door itself will cut signal probably 40%. Maybe more.

Ideally, you would put 2 zwave repeaters in every room. That would give you a really nice strong mesh. So in the video, there would be one repeater in the kitchen, and another over by the doors to the outside.

With the current generation of Z wave, pretty much any mains powered device except a smoke sensor also acts as a repeater. That includes light switches, plug-in pocket sockets, plug-in sensors, In wall relays, etc.

You just need to add a repeating device in the kitchen and you’re probably solve the problem.

The metal door is an entirely different issue because it’s going to completely screw up that particular kind of sensor after a week or two . Here’s the FAQ on that. But that’s actually a separate issue than the range.

Here’s some more stuff on range and repeaters. But basically you’re just asking it to go longer than it’s designed to. Zwave and zigbee devices are intended to be very low power which is what gives you the one to two year battery life.

http://thingsthataresmart.wiki/index.php?title=Repeaters

If you want longer range without putting in repeating devices, you’ll have to go to a different protocol. The Kumostat wireless tags can do it. But they cost more money and the interaction with SmartThings is a little more fragile. And the metal door still has the same problem.

Anyway, nothing wrong with the Z wave radio, nothing wrong with the hub, you’ve just gone too far for a single hop with that particular sensor. :sunglasses:


#12

Any metal blocks radio signal, ferrous metal ALSO messes up the magnetic sensor.

Wrap a device in aluminum foil and reception drops significantly. It’s electrical conductivity that causes the problem, not iron content.


#13

No.


(Never Trust @bamarayne) #14


(Scott) #15

Thanks for that, folks. Nothing that I wasn’t expecting.
So it looks like I need to get a US spec z-wave repeater somewhere between the devices and the hub?..


#16

Yep, that should do it. The problem is which one can you use. I usually recommend a pocket socket, but the problem is that it has to be one on the exact same frequency as your hub, which means a US pocket socket. So then you’ll need an adapter to be able to plug the pocket socket into your outlet.

Battery operated devices do not normally act as repeaters.


(Alex) #17

@skotl - The US Zwave uses 908MHz frequency which is also used by GSM phones in Europe. I can’t say whether that is the issue but I suspect it is illegal to use the US hub there as it is illegal to transmit on those frequencies without a license.

Also, if your house is made of concrete, bricks, cement, rebar, metal doors and frames, etc - all of that will reduce the range of RF. Typically the higher the frequency the higher the impact. I am not an expert on zwave but it is meant to be used as a mesh network so it uses very little power as it only needs to hop (max unobstructed 30m) to the next closest device and not necessarily all the way back to a central hub. Adding more plugged-in devices in your house will likely resolve the issue as the hops will be shorter (that is assuming all your equipment is just fine). HOWEVER, I really do not recommend using equipment that transmits on frequencies allocated to telecom companies… here in the USA, 902 to 928 MHz is an ISM band which allows unlicensed operation so there are lots of devices that use it (home phones, baby monitors, zwave, etc).

Quoting wikipedia: "Z-Wave uses the Part 15 unlicensed industrial, scientific, and medical (ISM) band.[15] It operates at 868.42 in Europe, at 908.42 MHz in the U.S. and Canada but uses other frequencies in other countries depending on their regulations. "

I am originally from Italy, although half my family is from the UK, and in my yearly trips back home I have always noticed how hard it is to get RF through walls of my home in Rome… while my wood and drywall home in Texas is much more RF friendly.

I would definitely look into adopting the UK model. There may be lower zwave device availability operating on 868MHz (EU frequency) but you might find a larger number of zigbee devices you can use instead. Those operate in the 2.4GHz ISM band which is common to most of the world.


(Alex) #18

I beg to differ… cell phones use that band in Europe and transmitting on frequencies allocated to cell phone companies is illegal. Whether there is a tower servicing that frequency close enough to Scott, thus causing issues, I don’t know… but I would not be surprised. More details in my post a bit further down.


#19

I Agree with everything said above except that I think you will find there are many fewer zigbee devices available in the U.K. that would be compatible with SmartThings than you would find in the US. This is a common complaint in the UK section of this forum.

While it is true that there is only one zigbee frequency, the zigbee standard allows for the use of multiple “profiles” and these are not all inter-operable. They don’t even use the same addressing structure.

SmartThings uses the “zigbee home automation” profile (ZHA 1.2). These devices much less popular in the EU than zwave.

In addition, different countries set different maximum ceilings on the transmission power of zigbee devices. The level allowed in the EU is about half of that allowed in the US, which means that many US zigbee devices are illegal to operate in the U.K.

There are some zigbee devices which use the ZHA profile and are available in the UK, in particular the Orvibo brand, but in general you have many more choices in each device class in the UK if you look for zwave rather than zigbee.

The main reason may be that Wi-Fi and zigbee operate in the same band and WiFi can drown out zigbee. This makes device placement much trickier for DIY installs.

Z wave operates in a completely different band and does not suffer from Wi-Fi interference, so it is generally easier for do it yourself installations. This probably contributes to the popularity of the protocol.


#20

This is all true, but it’s unlikely to cause a contact sensor which reliably works 4 meters from the hub to stop working 4.1 m from the hub.

I agree that it would be much better to adopt UK frequency devices.