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My 4G solar relay

How to level up from typical NBN satellite latency (and speeds):

to something more like:

I don’t get a 4G signal at my house/office, but there’s a good signal at the top of a nearby hill.

How to use it? There’s a thread about this at https://forums.whirlpool.net.au/thread/9xzljjk9 (and a wiki) for inspiration.

In putting mine together, I’ve tried to keep the number of moving parts down, and use “cheap but reliable” components to end up with something robust and “performant”.

Under $1500 for what’s shown here in this end-to-end diagram:

On the Hill

Here’s what I’ve got on the hill:

Plus battery and solar panel of course – the battery sits in the box in front of the Comfast unit.

The little white thing is a Comfast E5 (which came on a slow boat from China due to COVID)

which contains a modem to connect to the Telstra tower, and a wifi network to the house. Its powered by USB (5V, 2.5A; the specs say the E5 uses <12W).

Here’s what’s inside – a Quectel EC25-AU:

It only exposes a single 4G antenna (no MIMO unless you add another), and its a class 4 device (so no carrier aggregation), so its not the fanciest modem, but the speeds shown above are good enough for me, and having just 2 antennas is simpler. So as long as it proves reliable and sips little power, I’m happy!

Average power consumption (over a 4 day period) for my usage, is 0.35A. At 5 volts, that’s 1.75 watts, or 42 Wh per day.

The 2 antennas are just:

  • wifi: the “LIEHU” flat panel is an el cheapo $9 wifi antenna (claimed 14dbi)
  • 4G: LPDA antenna from https://www.ebay.com.au/itm/183762388396 which claims 9 dBi gain for B28. Its vertically polarized, but you can see I didn’t worry about that too much 😉

I built ROOTer 1907-2 for ATH79 (there’s a COMFAST CF-E5/E7 profile) and installed it.

ROOTer reports:

(that RSSI does vary to -65)

Battery is a DiaMec 18Ah SLA, https://www.jaycar.com.au/12v-18ah-sla-battery/p/SB2490

My solar panel is the JayCar 100W folding solar panel at https://www.jaycar.com.au/powertech-12v-100w-folding-solar-panel-with-5m-lead/p/ZM9174 which has a solar charge controller on the back.

But I wasn’t sure that solar charge controller was waterproof, so I wanted one I could put in the weather proof box.

So I got a Electus/Jaycar/Road Tech Marine MP3743 unit (rebranded ProVista SCP30 with wifi, see https://www.provistahk.com/wp-content/uploads/2020/05/Provista_Products-4.pdf page 20).

I selected this because of 3 features:

  • USB socket (this one claims 2.4 amp, more than some of the others)
  • Remote monitoring (power generation, battery state, power draw)
  • Timer

.. and the fact that I could buy it locally over the counter.

The reason a timer is of interest is to turn off the E5 during sleeping hours, to save battery power. But if the E5 is off, my weather station doesn’t upload (it can’t cache), so my weather record is compromised. Similar issue with any security cameras, so its much better if the E5 can run 24×7. It turns out that the load-on/off timer doesn’t apply to the USB socket, so its not even an option.

The load monitoring doesn’t measure the USB socket either (nor did it measure the power draw of the E5 when connected via non-USB? Have to double check this…). The ECO Solar app works OK for me, but could be better. God only knows why Electus/Jaycar/Road Tech Marine don’t employ someone to write decent English language instructions…

Since it doesn’t quite live up to expectations, you could use a much cheaper controller, and a $20 Jaycar MP3675 12V DC to USB convertor. (Plus a timer if you choose)

That said, the app does produce some real-time data:

(just ignore the load info) and historical data:

(Yesterday it rained all day, hence the poor power generation; today, it is only 10am, so that most recent bar will increase) Over August, it averaged maybe 60Wh per day, which is more than the 42Wh typically used.

At the House

At the home/office I use 3 pieces of Ubiquiti kit:

  • NanoStation loco M2, to connect to the hill (using its internal antenna) at 2.4 GHz
  • UniFi AC LR AP, to provide wifi around the house
  • EdgeRouter X SFP (ER-X-SFP), which provides power (POE) to both the above devices, and DHCP (the AP can’t do that). I’ve got a UPS powering the router, so this stuff will run for a while if the power goes out.

Troubleshooting

Things seem to be running smoothly.

I do have a cron job running on the Comfast unit to restart wifi periodically (after it crashed on me once). I don’t want to have to walk up the hill to reboot it. Although if you can send an SMS, apparently ROOTer supports a remote reboot-by-SMS. You send an SMS to the SIM card’s phone number, containing just:

::reboot!!

But if there is no Internet, the first thing I do is look at the NanoStation to see whether it is connected to the Comfast unit:

Bill of Materials

That’s most of it; there is no pole priced here, since everything is hung on or screwed to a gum tree 🙂

Next Steps

  1. I still have the Satellite NBN, so I should connect it to the router. Maybe I’ll route some traffic over it. But mostly, it is peace of mind if the tower in knocked out in a bushfire.
  2. Evaluate epever triron as a possible replacement for the SCP30. Mostly out of curiousity, and just in case…

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