Electron won't connect at remote site when plugged into PCB board

Hi -

This is my first post here although I’ve been using the Particle platform & the community forums for over a year. A simple forum search has been able to answer all my questions until now.

I have about 10 electrons currently fielded. Each of these uses a “carrier” PCB that I designed that utilizes header sockets to interface with the electron header pins. All of the electrons run identical code. Until now all of the devices have reliably connected to the cloud.

I recently fielded a device in an area that has -110 to -115 dBm of ATT LTE service, and -90dBm of ATT 4G service. These numbers were obtained during the site survey with an iPhone.

Despite the relatively good signal, the electron fails to connect at the site. The electron is configured properly, and works in the lab where I have about -70 dBm of ATT LTE service. The electron rapidly blinks green. Periodically, it will breathe cyan or a couple pulses and then immediately go back to flashing green. I have tried the following without luck:

1 - Replaced the antenna
2 - Replaced the carrier PCB
3 - Replaced the electron
4 - Attempted connection without peripherals connected

The situation even gets more strange; the electron connects almost immediately to the cloud if it is unplugged from the carrier PCB. However, back at the lab (in the -70 dBm signal environment) the electron connects to the cloud with no problem while plugged into the PCB.

I am currently at a loss as to how to proceed. I could try other antennas, but that seems like taking a complete shot in the dark. One theory that I am kicking around is that the electron is trying to connect to the very weak LTE tower and is ignoring the stronger 4G tower. On site my phone switches between LTE and 4G, and has better performance on the 4G tower. Is there some way to keep the electron locked onto the 4G tower? Does the electron even use LTE?

I really appreciate any advise that the community can give here. Thanks in advance!

The Electron uses 3G with 2G fallback.

2 Likes

Have you tried the Electron troubleshooting app or @rickkas7 electon_cellular app?

https://docs.particle.io/faq/particle-devices/electron-3rdparty-sims/electron/#electron-troubleshooting-app

Finding out what the 3G and/or 2G RSSI at the site would the first thing I would try.

2 Likes

I have not measured the 3G signal strength. I can go to the site and allow the electron to connect without the PCB and check the RSSI and cell quality. If it’s right on the signal strength threshold the PCB might knock off a couple dB and keep it from connecting.

No, I was unaware of those resources. Thanks for taking the time to point them out! I will visit the site and check the 3G RSSI and report back - it may be a few days before I make the trip.

If signal strength is the problem - and that seems likely - I may try to add a higher gain antenna.