HARDENED pi
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Don, there should be a battery to run the PI if the mains go away, and the battery has to be big enough to keep it up for the duration of any outage, or there has to be some smart way to tell Linux to stop, then remove power from the PI, then when the power is back, bring the PI back online.
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My nodes have a 2 amp gel-cel and the mains run a 14.2v DC supply to run the radios and charge the Raspberry PI. The radios run off of the mains power so only the NInoTNCs and Raspberry PI are on the battery. There is no protection for if the Raspberry PI runs the Gel Cel down. In one non-air conditioned site (mostly in the shade and well ventilated), I’ve lost 3 batteries in 7 years and two of the batteries were before I realized that my 13.8V power supply which is then dropped through a protection diode wasn’t enough voltage to keep the battery charged. I fixed that by upping the mains DC supply to 14.2V and put in the 3rd battery. The 3rd battery died, I think, because the mains power was off for 4 days. The site is in a wood shed (open at the eves) in the back yard of a ham’s relative’s house. Each time the battery died, the Raspberry PI also went offline and needed attention. It’s been 18 months since I put in the 4th battery. The batteries cost $10 each so that’s been the cost of my education. The other sites are easier to get to, are all air conditioned, and have also never had an outage for more than an hour. Only the woodshed site has ever locked up and needed a visit. All of my nodes use G8BPQ software running under Raspbian OS on a Raspberry PI. None of them have a fan for ventilation except that which is in the power supply. I’m in North Carolina where the humidity is high and the in-the-shade temperature is in the 90s during a summer day and in the low 30s during many winter night, below freezing rarely. Tadd - KA2DEW On Aug 30, 2021, at 3:21 PM, Don Ritchie <dritchie@...> wrote: |
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The first thing that comes to mind is, what are you trying to accomplish? You mention a remote site that is difficult to access. AFAIK, Winlink is mostly a messaging system and is generally used by an operator. VARA FM is just one digital mode used by the Winlink application to communicate. You can use traditional packet or a few other modes to communicate. As previously mentioned, VARA FM is a Windows only app, so that leaves out the Raspberry Pi.
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That being said, if you want to have some kind of digipeater or telemetry service or whatever at a remote site and want to use a "hardened" RPi, my suggestion is to use a MoPi2 power hat. This is a great device that provides several key things. First, it has two power inputs that accept 6-30VDC as well as a charging input from something like a solar panel. You have your primary mains power on one input and your back-up gel cell on the other. The charge input maintains the gel cell. If the main input drops below a preset level, or loses it entirely, it automatically switches to the backup gel cell. If power is not restored and the gel cell drops too far, it automatically does a graceful shutdown of the RPi. It has a single power button control for starting and stopping the RPi gracefully. For one remote situation I have used this, there is an RPi with the MoPi2 doing things. There is a main 12V power supply powering all systems, including the RPi, plus a gel cell backup for the RPi. In case of a long power loss that shuts down the RPi, there is a small Arduino device that detects when the RPi is shut down. When power is restored, the radio comes back on. The Arduino device senses the RPi is down and sends an ID over the radio periodically. Detecting that ID, I know the RPi is off. I can send a DTMF tone, which is detected by the Arduino and closes the control line to the RPi to restart it. That allows me to restart the system without a trip to the remote site. Hope that gives you some ideas. 73, Michael WA7SKG Don Ritchie wrote on 8/30/21 12:21 PM: SORRY, THIS MAY GET LONG ... |
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I've built a couple of remote solar powered sites. Here are some of my ideas:
I use Industrial SD cards. More reliable and just a few dollars more. SLCs are better but much more costly.? I have a DTMF decoder to do a reset on the pi.? I use APRS's telemetry function to measure battery current, voltage, power, solar radiation and cabinet temperature.? This device is easy to interface to the pi?? |
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9600 baud is doable with a DRAWS? HAT -- which also powers the RPi from the 12 VDC you have for your radio.? There is a metal case available for the Pi?+ Hat.? It also has a built-in GPS for time and location.? Use Direwolf for your software TNC. On Mon, Aug 30, 2021 at 2:18 PM Don Ritchie <dritchie@...> wrote:
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John D. Hays Kingston, WA K7VE / WRJT-215 ? |
Tadd KA2DEW in NC
Michael WA7SKG
Bill WA4OPQ
John Hays - K7VE / WRJT-215
Jouko OH5RM