DS10A Interference Problem

[coallen]

Hello everyone. I'm a new registration, but have often read through all the very useful posts in the past.

I've been working on getting my house setup with X10RF devices using the W800RF32A. I've been primarily using DS10A's and MS16A's. My initial plan was to setup an alarm system, but these devices have proved so fun to work with that I've been doing more of what I would consider home automation. It didn't take me long however to run into a problem. I'm hoping someone out there might have some thoughts as to how to solve it.

The issue is that the bytes being received by the W800 are getting mangled when more than one unit transmits at the same time. This doesn't happen very often, but often enough that it's noticeable. I currently have my system speaking when doors are open and closed and when motion is detected. This is currently for testing purposes only as it would get annoying pretty quickly if left running all the time. So the situation is that the system says a door has opened and then occasionally misses saying the door has closed. I narrowed the occasional miss down to a nearby motion detector.

I have been able to repeat generating the mangled bytes by using two DS10A's that open and close at the same time. If you're watching the data come across the COM port, it gets corrupt when the simultaneous transmission occurs. It doesn't happen every time, and the devices transmit their signal about 7 times in a row for each open/close sense, but as I said, it does still occur.

I know many of you are using a lot of DS10A's together, to monitor things like mailboxes and kitchen doors. So I wouldn't think I'm the only person who's run across this. I was thinking of maybe adding a second magnetic switch to the door further down it's length and connecting it to the same DS10A in parallel to see if I can get it to resend it's signal shortly after sending it's first signal. Or maybe adding a 555 timer to get it to resend it's signal.

Any thoughts? Thanks in advance!

 

[electron]

Hi coallen, welcome to CT!

That's a pretty interesting situation. I have several DS10As deployed as well, and have not run into this issue. I'm wondering how commercial RF sensors deal with simultaneous transmissions. If you don't get an answer here, I'd try contacting the WGL folks, they are pretty responsive and can probably give you some good suggestions. Keep us posted!

 

[SnyperBob]

Hi coallen,

I have been running the same setup for about a year now and I have never had the problem you describe. What software are you using for your automation? I know you said you can see the collisions or whatever by looking at COM traffic, but I thought it was up to your automation software to figure out whats going on

I have been using Virtual Crib (vcrib) for free for a long time with my setup. It's free you can try that out if you got some time. www.thevirtualcrib.com

I have a build thread over there that explains my setup.

The only other thoughts are that your w80orf is bad or something. I have had issues where some of my cheap x10 devices aren't working correctly (motion detectors usually). I've never really had a problem with my setup, so I've never analyzed my COM traffic that much. I guess the problem would either be your transmitting devices or your receiver, but I know that doesn't help much :blush:

 

[coallen]

I'd try contacting the WGL folks, they are pretty responsive and can probably give you some good suggestions. Keep us posted!

Thanks Dan. I did contact WGL support and this was their response:

"The problem is X10's RF format. This is a very common occurrence and so far no one has came up with a solution other than replacing X10's devices for much more expensive ones."

I responded back, asking if there might be a way to detangle the bits if I knew what data I might be expecting. This was their response:

"It is not the data format, but the modulation format. X10 just switches the 310MHZ carrier on and off for each bit making it very easy for any outside signal to corrupt the original."

What I'm planning on playing around with is adding a passive reradiator to the DS10A. I don't appear to have the ability yet to post links in this message, but if you google dave houston passive antenna you should find it.

My problem is that my motion sensor in the stairwell is interfering with the close door signal. When someone opens the door, steps into the stairwell, starts up the stairs and then closes the door, with their arm behind their back or with their foot (as they move up the stairs), the signals get sent simultaneously (I've become quiet adept at reproducing the maneuvers necessary, it's quite amusing to watch I'm sure). I have the motion sensor there so that I can turn the downstairs lights on when someone is coming down the stairs at night. If I can get the DS10A to overpower the motion sensor, then I will still get the motion signal when someone comes down the stairs and then the motion signal will be overpowered when the door sensor transmits the close door as someone is going up the stairs. I'm also considering replacing the motion sensor with a couple of pressure sensors on adjacent steps.

The underlying issue isn't a huge deal normally as it's very unlikely that other sensors will be transmitting at exactly the same time (though it can happen with lots of motion/door detectors). I can't really fault X10RF as the basic idea was to operate as a security device (where any device could trip the alarm, so a missed signal somewhere isn't a big deal as something else will transmit another signal--plus the idea is that there's not a lot of activity in a quiet house).

After doing lots of research on this topic, I noticed that Spark Fun sells cheap ($3.95) transmitters and receivers ($5.95). I've ordered a couple of each and may tinker with creating my own transmitter/receiver using a microcontroller to send a signal out on a semi-random basis over a period of 10 or 20 seconds. That would make it more likely that signals wouldn't collide. Something like this would be cheaper to implement than ZigBee. My dad came up with an idea where I could use a microcontroller and the insides of one of those slimline wall switches. This would make it very easy to implement. I could probably stick the whole thing into a small box no bigger than the ds10a and put it right next to it.

Then again, after having run it continuously over the last week, I only seem to be missing signals occasionally in the scenario described above, and not once in another scenario, so it's probably not a big deal.

Thanks!

 

[coallen]

I know you said you can see the collisions or whatever by looking at COM traffic, but I thought it was up to your automation software to figure out whats going on

I'm using software of my own creation, written in C#.

The only other thoughts are that your w80orf is bad or something.

My dad has also been able to reproduce the same results with a different W800. Plus the W800 support people have acknowledged the issue is with the X10RF transmission format itself.

Thanks for your response. I'll have to check out your site. I'm always interested to see what other automation owners are up to!