X10 Community Forum
💬General Category => General Discussion => Topic started by: BryanS19 on November 20, 2019, 03:49:16 PM
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So a while back I got the bright idea to take some of those cheap ESP-01 boards, a DHTxx sensor, some glue parts, and spin up a cheap board to make a deployable temp/humidity sensor. While that worked just fine, and I went through a few revisions of the product, I ran into some interesting troubles.
The first problem was the DHT sensors aren't reliable enough. They would randomly stop talking and require a power cycle to resume operation. I think there are some other issues as well, being the second problem:
The second problem, the ESP-01 I was using spews RF out at just below 320MHz, with other stuff floating around the same area. While one of these deployables didn't do anything, the 10 or so I put online made the signal from the X10 wireless gadgets I have unreliable AND knocked out my 318MHz garage door opener's receiver. You could literally see receive lamp on the opener "on" all the time, indicating it was seeing something on it's band. Turning off all of the deployables restored normal communications with all devices. I believe this noise was also causing some of my DHT sensor issue, since they seem to be susceptible to RF as well. I know the opener's radio is wide enough to see the noise from the ESP8266's, and I have to assume that the X10 wireless modules are wide open as well, so were being overloaded by the noise.
I experimented a little with ESP32, but they have the same issue, and the FCC certs even state noise at 319.9MHz. Oh well, I guess, now I just need to dispose of a stack of boards, fortunately they were cheap!
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Since X10 is 310.00MHz and its receivers are not too selective. I am not surprised if the ESP modules where spewing RF that X10 could be compromised.
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I figured the receivers were wide open with no filtering. Once I determined what the ESP modules were doing, it was no surprise as to the results.
All of the ESP-xx modules seem to leak this, so things like Sonoff switches could be a problem if used with a X10 wireless system. The ESP-32 modules are just as bad.
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It's been several years (10+) since I tested this so the exact details are a bit hazy but...
Older X10 RF transceivers are super-regenerative which makes them susceptible to being triggered into oscillation by ANY strong RF source. They self-oscillate (which may be what the OP is seeing) and this can interfere with nearby devices. I believe my testing was with multiple X10 receivers where I found they needed to be several feet apart to avoid problems.
Even the 120kHz PLC signals radiated from the powerlines can cause problems for the super-regenerative receivers .
Super-regenerative receivers are super-inexpensive so they were widely used in garage door openers and other RF devices. As inexpensive single chip super-heterodyne receivers appeared, they have largely replaced super-regenerative designs.
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I didn't dive into the X10 problem too much, just enough to say "Yeah, the ESP8266 is spewing out RF ~receive frequency of the modules, so it's probably overloading the receiver and causing problems."
The garage door opener wouldn't be a problem if I didn't have a Linear (Corporation) unit. It uses a strict 318MHz frequency, so even if it's only got a bandpass of 4-5MHz before it hits the dirt, that's still enough to allow the noise from multiple ESPs to cause problems. Other manufacturers used 390MHz, and now use a strict combination of 310, 315, and 390MHz to reduce this kind of interference (and stay off the bands that Uncle wants to use...)
I was able to directly observe cause and effect by powering 1 ESP32 module within 10 feet of the opener. ESP32 off = no receive indicator, all operation normal, ESP32 on = receive lamp on continuous, no remote operation.