Lightning detector AS3935: Part 3 of 3

Clockwise from top left: ADSL splitter, AS3935 (in vise), ESP-12E, relay module, powered USB hub, modem and POTS analog phone. All blinkenlights are go.

In the last part of this series, the AS3935 detector is hooked up to the ADSL line, and the ESP-12E is programmed to disconnect if there is a thunderstorm overhead. When the storm moves more than 8km away it will reconnect after 30 minutes.

As first mentioned in Part 2, it publishes to a local MQTT server, and also subscribes to it. This is to allow it to disconnect and reconnect the ADSL modem remotely on demand. For the last six months or so my TM Streamyx (now 'Unifi') ADSL2+ line has been unstable; dropping and reconnecting every few hours or worse. This constant failover to 3G tended to overload the TP-Link MR3420. Disconnecting the phone line during the bad periods seemed to give it some relief.

As before, the AS3935 can be quite sensitive to inteference. I ended up using separate shielded USB charger cables for 5V for both the ESP-12E and the relay module. At worst, excessive interference resulted in permanent false alarms for 'storm overhead'.

Also you can reduce false alarms by additional shielding. I partially encased the AS3935 module in a steel vise to stop it triggering when I turned on my fluorescent lights. Do not shield it completely or there will be nothing detected.

Jury-rigged steel vise shield for the AS3935

Connecting to the telephone line

My incoming POTS line has two wires, but a standard US RJ11 phone jack has at least 4. Our benighted Talikon Malaysia uses British standard (BS 6312), but most devices (not phone line) comes in the US RJ11 4-wire format, which is what I used.

Lanshack has a good page on the pinout:

The 4 wires in my RJ11 jacks cover pins 2 to 5 corresponding to Pair 1 and Pair 2. Pair 1, ie R1 & T1 at pins 3 & 4  (ie red & green wires) seem like a good starting point. I took out the modem ADSL cable, ie one with RJ11 jacks on both ends and cut it in two. The red and green cables are easily accessible.

Start with your modem phone cable, and cut in in half 

Modem cable with just Pair 1 reconnected

I verified my guess by reconnecting just Pair 1 and used my modified cable to reconnect the modem to the phone line. My ISP TM (TMnuts for short) uses ADSL2+ and that did not seem to affect my modem operation but your mileage may vary. Since broadband runs at 1Mbps up to 20Mbps changing the phone cables characteristic impedance with discontinuities like connectors and joints might affect it big-time.

Also, it would be wise to hook up the ADSL splitter and the POTS analog phone to see if they still work. If the joints did not affect your phone or modem setup, go ahead and hook up the relay module. A note of caution: disconnect the phone cable from your ISP line before you rewire. Phone line voltages are around 40Vdc and are usually safe to handle. This can change to as much as 100Vac if someone tried to call you on that phone. Be careful- phone lines can be hazardous! so you really do not want to touch the relay module when the phone is ringing.

Relay module cabling, clockwise from top left: 5V power, R1, T1 and TTL serial

I wired up the ISP side to relay Normally Open and the modem side to Relay Common. This means the relays need to be on most of the time and more power (about 100mA at 5V) will be used. The advantage is if the first strike took out the power mains, the modem will not be reconnected to the ISP.

If you only have the single relay version just switch T1 to break the circuit. This should help a lot and reduce the power of a strike, but my guess is the lightning strike can still reach the modem via R1 and if it is near enough will then complete the circuit to modem Earth or failing that to modem DC GND.

Of course if a strike is almost on top of the modem it will probably jump the relay air gaps, but the modem will be the least of your problems then. It is advisable not to go near the setup in a thunderstorm, even after the relay module has disconnected the modem. I have noticed the electronics twitching on following strikes even without power, ie after the first strike has taken out the power mains.

Software  

For esp8266 MQTT client I used pubsubclient. It was quite painless to use and its sample code worked first time with mosquitto so I will simply skip ahead to the complete version. For details on the mosquitto MQTT server, see Part 2. The nice thing about a local MQTT is that the AS3935 can then be used to disconnect more than one IoT device, for example the autogate, POTS phone extension and the satellite TV.

You can get a copy of the software from github.

To look at the MQTT output:

$mosquitto_sub -t 'AS3935/messages' -v

To turn on the relays

$mosquitto_pub -t 'AS3935/commands' -m '1'

Or you can do it from a smartphone App. I used MyMQTT. For now, you need to be in the same WiFi access point as the AS3936.

I used MyMQTT on my Android phone

As usual we keep monitoring for bugs and tuning the calibration settings. I tend to desensitize the alarms as Malaysia gets many violent but localized (ie usually not widespread) thunderstorms, and I do not want to trigger a disconnect until it is right on top of the AS3935. I also have fluorescent lights and a hot shower which tends to set it off unless I use a threshold setting of 9 and above.

This is my typical output for a real storm:

AS3935/messages 14:08:59 2019.11.19 Lightning detected 8 km away
AS3935/messages 14:09:04 2019.11.19 Lightning detected 6 km away
AS3935/messages 14:09:13 2019.11.19 Disturber detected
AS3935/messages 14:09:21 2019.11.19 Disturber detected
AS3935/messages 14:09:22 2019.11.19 Disturber detected
AS3935/messages 14:09:30 2019.11.19 Lightning detected 6 km away
AS3935/messages 14:09:45 2019.11.19 Disturber detected
AS3935/messages 14:10:07 2019.11.19 Storm overhead, watch out! Disconnecting the phone lines ..

AS3935/messages 14:20:13 2019.11.19 Disturber detected
AS3935/messages 14:31:10 2019.11.19 Lightning detected 12 km away
AS3935/messages 14:32:40 2019.11.19 Lightning detected 12 km away
AS3935/messages 14:33:18 2019.11.19 Disturber detected
AS3935/messages 14:36:02 2019.11.19 Disturber detected
AS3935/messages 14:40:08 2019.11.19 Reconnecting the phone lines ...

Once it disconnects, the software waits for the storm to move 9km away, waits a further 30min and then automatically reconnects.

At this point we just sit back and watch the light show. Happy Trails.

Lightning Detector AS3935: adding Serial Relay Module and MQTT Server Part 2 of 3

In Part 1, we interfaced the AS3935 lightning detector to an ESP-12E using SPI. In Part 2 here, we add an ESP-01 2-channel WiFi relay board and also set up an MQTT server.

But first, some test results. After running the system in Part 1 for a few weeks we know that:
1. There are many false (ie 'disturber') alarms
2. Some lightning strikes are incorrectly classed as 'disturber'
3. The little antenna is directional, so be careful positioning it
4. The AS3935 and relay module are best on separate 5V wires, otherwise there may be too many false alarms
5. The settings that worked for me are: Noise Floor: 3, Spike Rejection: 0, and Watchdog Threshold:2
6. There is good correlation between actual lightning strikes and the AS3935 readings
7. I have good results disconnecting the relays when the lightning is less than 5km (ie 'storm overhead') and reconnecting it 30 minutes after  lightning strikes are further than 8km away.

2-channel wifi relay module

ESP-01 2 Channel WiFi Relay Module

I got mine from lazada.com for RM27 (about USD4) each. Unlike the other ESP8266 relay boards this one has a separate CPU to activate the relays and instead of using precious GPIO pins you can do it with the serial port UART0.

makerrelay has a good writeup on a very similar module, complete with schematics and identical relay switching commands. Even better, libretto (Sergiy Zaschipas) shows you how to reprogram the relay CPU.

I can not only replace the ESP-01 with a NodeMCU ESP-12E, but I can now add relay 'channels' by simply adding more relay boards. I do not even have to use extra GPIO pins - the same TTL serial port UART0 can drive all the relay boards.

Another convenience is the relay outputs need not be reset especially since the ESP8266 is sometimes best reset if it is unable to reconnect to WiFi. If the relay CPU is reprogrammed, the ESP8266 may even read back the relay states. Since the AS3935 drops the phone line when a storm is overhead it can actually cause WiFi disconnects.

Based on some of the board markings, it is possible the original design is by LC Tech. LC Tech also provides documentation.

NodeMCU ESP-12E Pinout

You connect GP101 (also TXD0 or TX) to the pin (ESP-12E bottom right) marked 'TX' on the relay board. Connect up the adjacent GND pin to the correcponding relay module pin and you are good to go.

Relay module, solder side

Note that if you want to supply power to the relay board you need 5V which is on the other column of pins (VIN) of the ESP-12E, and not the very tempting 3.3V pin.

The relay commands are:

//Hex command to send to serial for close relay
byte relON[]  = {0xA0, 0x01, 0x01, 0xA2};
//Hex command to send to serial for open relay
byte relOFF[] = {0xA0, 0x01, 0x00, 0xA1};
//Hex command to send to serial for close relay
byte rel2ON[]  = {0xA0, 0x02, 0x01, 0xA3};
//Hex command to send to serial for open relay
byte rel2OFF[] = {0xA0, 0x02, 0x00, 0xA2};

To turn on relay 1:

Serial.write (relON, sizeof(relON));

It is that simple. My setup now looks like this:

AS3935 SPI and Relay serial port cables consolidated to one 2-headed monster. Note the 5V VIN cable on the far right. System power is via the USB cable (silver)

Top left to right: ESP-12E (partially hidden), relay module and AS3935

MQTT Server

Now that I have a way of disconnecting the ADSL modem, a convenient way to monitor the AS3935 results would be nice. Initially I simply printed the results using Serial.print() and got the output via the Arduino IDE Serial Monitor.

This worked when I am at my work station but pretty soon I was printing out to my Adafruit MQTT feed. This worked much better until a lightning storm came close enough for the relay module to disconnect the ADSL modem at which point the Adafruit connection got interrupted.

Now my WiFi does have a 3G failover, but it takes precious seconds for the Adafruit feed to re-establish itself and vital AS3935 messages are often lost. So one of the things to try would seem to be a local MQTT server, which could capture and retain my MQTT messages and if necessary upload them to my Adafruit feed for when I am offsite.

It sounds like a lot of work, until along came Mosquitto. Since my main station is still Slackware 14.2, I got my SlackBuild here:

As usual douwnload the SlackBuild tarball and unzip it:

$tar -xvpzf mosquitto.tar.gz
mosquitto/
mosquitto/slack-desc
mosquitto/README
mosquitto/mosquitto.info
mosquitto/doinst.sh
mosquitto/mosquitto.SlackBuild
usr/man/man8/mosquitto.8.gz
usr/sbin/
usr/sbin/mosquitto
usr/share/

Then download the mosquitto source code (from the SlackBuild link not the Eclipse one) and copy it into the mosquitto slackbuild directory. Then all you need is

$./mosquitto.SlackBuild

And then a Slackware install:

$upgradepkg --install-new /tmp/mosquitto-1.6.7-x86_64-1_SBo.tgz

Next you need to set up a mosquitto user:
$vi /etc/mosquitto/mosquitto.conf

And add the line:
user mosquittouser

If necessary create the new user:
$adduser mosquittouser

You start the server thus:
$mosquitto -c /etc/mosquitto/mosquitto.conf
1572678454: mosquitto version 1.6.7 starting
1572678454: Config loaded from /etc/mosquitto/mosquitto.conf.
1572678454: Opening ipv4 listen socket on port 1883.
1572678454: Opening ipv6 listen socket on port 1883.

And to check use the included client subscriber:

$mosquitto_sub -t 'test/topic' -v

The publish:

$mosquitto_pub -t 'test/topic' -m 'hello world of mosquitto'

And that was all you need. I suspect it is even easier in Debian/Ubuntu. The next thing I need would be an MQTT client for the ESP-12E, but that is another story.

So till then, Happy Trails.