Presence Sensors and ZigBee Reapeaters


(Paul Ockenden) #1

Picture a large house with a single hub, and perhaps half a dozen ZigBee repeaters (perhaps Outlets) dotted around the building, to form a mesh.

Now with most ZigBee devices that’ll be fine, because the ‘things’ will stay in one place, so will always talk to their associated repeater.

But Presence Sensors are different. You could be anywhere in the large house, but you’d still want to be seen as ‘present’. So they need to be seen from anywhere.

However, is this going to work? Surely the sensor will have picked the hub or one of the repeaters as its parent when initially paired, and it’s going to show as ‘away’ when it moves out of range. That is, if I’ve understood that blog post about meshes and repeaters that everyone normally refers back to.

Am I right? Or will the presence sensor report back via ANY of the repeaters?


Smart things Presence Sensor per room?
#2

the SmartThings presence sensor is goofy. There are many many weird things you can see with it. So if you are seeing wonkiness, my own first guess would be that it’s because of that device specifically.

What does “Away” mean?

You know how SmartThings decides that particular device is “away,” right? It’s set to check in every 30 seconds. That is not configurable. It’s always once every 30 seconds.

What is configurable is the number of missed check ins the cloud will allow before it arbitrarily defines the Presence sensor as “away.” For example, if you have a presence sensor which keeps bouncing back-and-forth between home and away usually the first thing support will do is increase the number of allowed misses. So this is not a zigbee activity – – it’s all software in the cloud. The check-in is zigbee but not how the account responds to it.

Keep the Battery fresh so the signal is consistent

Low battery strength can absolutely drive the system bonkers. One of the things that it does is throw off the 30 second timer. So you should Never use a rechargeable battery in one of these devices. And change out the battery whenever it gets to 50%.

Repeaters and the presence sensor

The presence sensor is most accurate if it never uses a repeater. I’m not saying it can’t use a repeater, because it can… But again there’s a tendency to throw off the 30 second timer. Indirectly, anyway. I don’t want to go into all of the technical details but it just works best if the presence sensor spends its time at home about 10 m from the hub (and from any Wi-Fi transmitter) and then gets picked up and taken out of range within a minute or so. If it’s more than one hop from the hub while it’s also “home” Peculiar things can happen. Although it may be fine if you leave it in your car and it’s always connecting to the same repeater in the garage.

Where things will get flaky is if it moves around your house at a distance of more than one hop from the hub but you still want it to always show as home. It will work OK for some people, but it definitely won’t for others. This is one of those “all home automation is local” situations.

The time it takes to find a different repeater and get the message through may cause it to be tagged as away even though it’s really there. Other zigbee devices don’t have the same issue because the cloud isn’t monitoring their check ins in the same way. An occasional delay for them is no big deal.

More discussions

There are lots of threads in the forum on the presence sensor but the short answer is it works great for some people and not at all for others. It is definitely subject to Wi-Fi interference. It works best with the battery 50% or above. And the time out parameter is configurable but only in terms of the number of missed 30 second check ins allowed for the grace period.

Oh, and if you’re using it in a car, adding one zigbee repeater in the garage may help a lot. Notice that in this last case, though, the presence sensor only has two locations from the hub’s point of view: in the garage or away. So it only talks to one repeater on the network, the one in the garage.

Short Answer: Give it a permanent home

So the short answer is if you’re going to use the smartthings zigbee presence sensor, use it as a “crossed the geo-fence” indicator and pick one place in your home where it will always live when you’re not away. :sunglasses:

More on the presence sensor here:


FAQ: Mapping your ZigBee network with Digi's XCTU
(Kevin [Yorkshire UK]) #3

I have done this but it doesn’t quite work out as expected…

When home my presence sensor is normally always in my utility room as that is where we hang the keys. The utility room has two outlets (repeaters) but is also partially in range of the hub. The outlets are less than 2m line of sight from the presence sensor so a good solid path. However when home my presence sensor constantly leaves and returns. I suspect the sensor is choosing the weaker direct to hub route rather than what would be a very solid path via the outlet. Is there any way I can force it to use the outlets as repeaters instead of choosing the flaky direct to hub path ?

When returning home I am quite surprised at the range of the fob sensor. ST detects the returning fob about 50m away from home and this must be via another repeater path as it’s the opposite end of the house.

Just so I understand - when the fob returns to the house and is then placed in the utility room does it re-negotiate a path or has it some memory of previous paths ? Would it prefer a weak direct path to a stronger repeated one ?

Or possibly is it because upon return it passes close to the hub and so picks that path up and then doesn’t fully lose that when it is placed in the utility room even though a better repeater path is available ? In which case these retentions of poor paths (even when stronger ones are available) is likely what causes the leave/return seesaw for many people.


(Paul Ockenden) #4

Could it be that the fob is constantly flicking between the two, and getting confused as a result?

If it’s practical, try unplugging one of those outlets and see whether you still get the problem. If it goes away, perhaps consider replacing one of those two outlets with a Z-Wave model.


#5

Great info here, but . . .crud, I think I have a problem.

I’m not strong with the technical side of this, so bear with me.

I’ve had repeated flakiness with the arrival sensors. They work great at accurately sensing real arrivals, but have the all-too-common problem of departing/arriving on their own when they’re resting inside my house.

Today, I have one ST outlet (which is a zigbee repeater) in my house, in addition to my hub.

Given how bad my arrival sensors have been performing, I just ordered two additional ST outlets … that I didn’t actually need. I bought them solely in the hope that I could form a better zigbee mesh, with more accurate coverage inside my house, and eliminate the erroneous departing/arriving issue.

If I’m reading the above correctly, it sounds like more zigbee repeaters throughout my house could actually make my Arrival Sensors more prone to error and worsen the situation? Is that correct??

(If so, accckkk!!!)


#6

No, fortunately the guesses described above are not how zigbee mesh works. If it did it would not be at all suitable for home automation deployments.

You can feel comfortable that as long as you have done at least one zigbee heal since all the devices were first added the arrival sensor will use the best available path. No matter how many repeaters you have. :sunglasses:

The issue of the arrival sensor getting confused and thinking you left is an entirely different issue. Sometimes it’s a platform issue. Quite often it’s interference from boosted Wi-Fi. (I have this problem with my own home. The arrival sensor will work fine for much of the day, but on many days right around 330 pm it starts bouncing back-and-forth. I suspect one of my neighbors has boosted Wi-Fi and a teenager gets home from school around that time.)

Support may be able to help, there are a few things they can do on their side. Additional zigbee repeaters can only help, not hurt. But sometimes the set up at one particular location just doesn’t work with the arrival sensor, and then you have to look for alternative methods for Geopresence.


#7

No. Zigbee takes signal strength into account when selecting a path. As long as you have done at least one network heal since adding all of the devices you can feel confident that messages will negotiate the best path, no matter how many repeaters you have. This is one of the intended advantages of Mesh. If a device tries one repeater and it’s busy and then tries another one it doesn’t sign off from the network in between. So there’s no problem with shifting from one to another, that’s part of the intended topology. :sunglasses:

You can easily do a network heal to make sure everything is up-to-date. Have all of your zigbee devices on power, and the arrival sensor in its usual place.

Now take the hub off of power including taking out any batteries from the hub. Leave the hub off of power for at least 15 minutes. Over this time all of the zigbee devices will go into “panic mode” as they realize the Coordinator is off-line.

Now put the hub back on power. All of the individual devices will rebuild their neighbor tables. This can take a while, so you might not see improvements until the next day. For this reason, it would be best to leave the arrival sensor in its usual location for a few hours, but it’s not a disaster if you don’t.

If you don’t see improvement after that, contact support (there are a few things they can do from their side). Otherwise, it may just be a local interference problem. See the thread I linked to in the post above this.


(Kevin [Yorkshire UK]) #8

I have done a few network heals (with removed hub battery) and it has helped some devices but I think the treatment with a presence sensor maybe different as to how it rejoins the network when it returns.

Often after a heal my presence sensor works well until it leaves and then returns.The last comment in my previous post was surmising that having found a good direct path it then retained that path as it became weaker even when better paths via repeaters became available. I was uncertain if it would renegotiate unless the path actually failed.

I have a similar issue with WiFi in my house where devices keep hold of weak access points even when much stronger ones are available. I couldn’t understand this behavior but now understand why. It’s because there is no guarantee the alternative access points are on the same LAN but this shouldn’t be an issue with ZigBee.

WiFi interference in that particular area should be minimal, No detectable access points from my iPad - but yes that could be a concern nearer the hub.

I’ll try contacting support and see what they say.

Paul - I’ll try your suggestion and reduce to one strong outlet although actually I suspect there are three if not four outlets in wireless range. Worth investigating. I took the sledgehammer approach and added quite a lot repeaters to my home to try and create a robust ZigBee mesh. If this were the problem it’s slightly awkward as a washer and a dryer are the two devices on the outlets and I log/graph energy consumption and advise on cycle remaining time / finish - so switching to Z-wave would require a few tweaks to keep that functionality. I also don’t have good Z-Wave reception in that room except on the direct to hub weak path.

suth - let me know how you get on. I’m just guessing at a possible explanation so I’d remain hopeful that your new outlets will fix it for you.


#9

I understand what you’re saying but it wouldn’t produce the behavior you’re seeing.

Your arrival sensor attempts to check in with the hub every 30 seconds no matter where it is. It could be 20 miles away, it could be in your utility room. Every 30 seconds it attempts to check in.

Your smartthings cloud account marks The arrival sensor as “away” when it has failed to check in for a specific period of time. The exact amount of time can be changed by support, and often the first thing they’ll do if you have a “bouncing” arrival sensor is just to extend The grace period. Note that this doesn’t change how often the arrival sensor checks in – – that’s always once every 30 seconds. It just changes how long the cloud account takes to mark the device as “away” when no checkin has been received.

This set up is completely different than the way Wi-Fi, which is a continuous connection topology, would work.

It’s not a situation where you can stand right on the boundary of your covered range and take one step forward and be present, take one step back and be away, take one step forward and be present, etc. You could do that with the Wi-Fi device, but not with the arrival sensor.

That’s because the “present” function for the arrival sensor is not an in range/out of range measurement. Instead, it’s a timebased “hasn’t checked in” system. That’s all. You could step back and forth across the coverage boundary 25 times and the hub wouldn’t even notice. Because it’s not a continuous connection topology. As long as you got just one message through during the allotted grace period, it doesn’t matter what you’re doing the rest of the time.

So there’s way more than enough time for the arrival sensor to try one path, have it fail, and shift to an alternate path before the grace period is up. In fact it probably has time to try three or four.

As long as there’s one good path, a message should get through. Which is why having multiple repeaters available strengthens the mesh.

When you’re seeing the ping-pong affect, it’s usually local interference which is crushing zigbee signals briefly, but long enough to miss a multiple check ins.

The next question is usually “then why don’t all of my zigbee devices go off-line?” And there are two answers to that. The first is it some of the May be, but you don’t notice because they keep coming back. And the second is that of all the zigbee devices that work with SmartThings, The arrival sensor intentionally has the weakest signal in order to limit the radius of its detection area. So it’s always the one that shows the most failures.

Anyway, I hope that helps make things a little clearer. The arrival sensor is sending a lot of messages. Some get through, some don’t. All you need is for one to get through during each Grace period And it will be marked by the cloud account as “present.”