Remote Switching Power to Radios

 I run a Winlink RMS at the house and occasionally encounter software issues that will take it offline for a few hours. This gets frustrating when Trimode encounters a serial port or soundcard error and spends hours trying to self correct. Trimode has a mechanism to prevent an excessive number of restarts but it is excessively high and out of all its menus there isn't one to change this setting lower. All of the Winlink sysop programs include a feature for offline notifications but if you're hardware/software are offline and the Winlink programs still have connections to the CMS you won't receive these notifications. In those instances where Trimode is struggling, it will go through all of its restarts (approx. 50) then stop itself and the minimum alert time is 2 hours after that failure to start. I've done all I can in Windows registry to standardize my USB devices so the programs always find their designated device but things still pop up intermittently.

I have the whole system including the server running off of 12v power with battery back up. The 12v power supply is also connected to UPS battery back ups. I can always restart the computer remotely if it has an internet connection. This should rarely be a problem because it has ethernet to both my home fiber as well as a Starlink Mini. The DRA 36M as well as the Motorola CDM 1550 to which it is connected for VHF packet have never been a problem. The IC-7300 has been very reliable but it is an intricate machine and has led to the aforementioned issues in Windows in the past. Additionally, the Pactor DR-7400 derives its power from the Icom's accessory port (p.70) and it too has developed issues in Windows after some time. This means the only reasonable way to power cycle the Pactor modem is to power cycle the radio. I currently have no means of doing this remotely.

I started my search for a self contained, internet connected (smart) relay capable of both switching and obtaining power from 12v. This became much more complicated than I anticipated. Most "smart" devices are tailored to home automation and imply 120V AC power is somewhere in the circuit. A few tailored industrial devices are capable of the amperage I was initially searching for but had superfluous features and unreasonable costs, all exceeding $200. I considered developing something with an ESP32 and another capable relay, normally closed, pulled high to open. This is still an option but I wanted to test something off the shelf. 

I finally realized that running at 50w, and almost always in receive, my amp draw requirement was negotiable. After much deliberation, I acquired a Shelly 1 Gen4. This smart relay has "dry contacts" so the switched voltage and powered voltage can be separate although I don't need this. It does however accept 12v with no modifications. A higher capability Shelly 1PM Gen4 include power monitoring and previous generations accepted 12v however Gen4 does not. Both are Matter compatible so I am able to add them to my Apple Homekit with zero additional effort. 

They Shelly 1 has many more features than I expected in a $24 device including bluetooth, zigbee, dual wlan client, wlan relay, GPIO, scripts, as well as all of the smart device features. I currently have it configured to power on 60 seconds after any power loss so that it always remains connected. I've read tales of people converting the 1PM to accept 12v but have not seen exact instructions. I have acquire both devices and will experiment with modifying the 1PM for 12v to obtain the added monitoring and power usage features. My main concern is over drawing through the Shelly 1 as it is only rated for 10a at 30v. This should be acceptable for my short duty cycle but to monitor power for guarantees currently requires additional equipment.

Below are several pictures of both devices' internals. The 1 has a blue shell and the 1PM is red. I currently have the 1 connected to Anderson Powerpoles (generic from Amazon) for in and out with taps to power the device. My goal is to duplicate this wiring after modifying the 1pm. You will see the positive (red) goes in and out of the device and the negative (black) is straight through. 

Device in Homekit

Shelly 1

1 PCB rear

1PM PCB rear

1 capacitor

1PM capacitor (same as 1)

1 capacitor

1PM capacitor (same rating as 1)

Empty shells (red 1PM, blue 1) [note reset butons]

PCB rear side by side



PCB front side by side





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