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Car rnode

Cars end up all over the place and so are great for testing and extending a lora radio mesh. It is most convenient if the rnode carries on running for as long as possible after the car has stopped running. Therefore this build (see below) uses an uninteruptible power supply (UPS) that keeps the rnode up and running while the car is parked. When the car is used, the UPS's batteries get charged, and the rnode will then hopefully be working again for about 24 hours even if the car is parked. If the rnode switched off due to the UPS's batteries being flat, the UPS is designed to re-start the rnode as soon as the car starts. In practice, if the car only runs for just two hours a day, the UPS batteries deplete after a while. This is because the rnode and Raspberry Pi 5 need about 48 Wh to run for a day, and the car in 2 hours only provides about 30 Wh with the power adapters listed in step 4 below.

Parts list:

  1. Rnode with battery: Rnode using Raspberry Pi 5 and Geekworm X1206 UPS.
  2. Car: Toyota Proace City Team Deutschland edition (same model as as Citroën Berlingo, Fiat Doblò, Opel Combo and Peugeot Rifter / Partner Tepee) with under-roof boot compartment.
    3. Antenna on car Compartment under roof of car.
  3. 12 V socket in car (cigarette lighter type socket): The car has a 12 V socket that is rated to 120 W.

  4. Option 1:

    USB adapter such as SYNCWIRE 90 W Cigarette Lighter USB C PD45W & QC45WCar Adapter or similar. This one does not sit tightly in the cigarette lighter socket, but is OK. There must be ones with a tighter fit.

    A USB-C to USB-C cable of suitable power rating and length to reach the rnode. The image below shows that the adapter above seemed only to provide about 16 W or so (measured with a USB power meter).

    12 V socket in car. 12 V socket in car with cables running to back and up to compartment under the roof.

    Option 2:

    Car power supply e.g. by HKY, Universal, 12V 5A that allows you to use the 5.5 x 2.1 mm DC power jack of the rnode (specified to 10 A) and that might supply higher power that the USB-C solution above. That adapter actually also only delivered 16 W, so is just an alternative and not an improvement.

    The measurement was made using a Buck converter with display set to 12 V and maximum current limit, using some wire and two jack adapters to connect the Buck converter in series between with the car power supply jack output and the rnode power input 5.5 x 2.1 mm input jack socket.

    Current and voltage measurement tool. Power from car power supply above.
  5. Antenna fixed to car roof: consists of an antenna and magnetic base to attach to the car roof. The antenna itself is from the product Sirio - SKA 901 C (Product code: 510901 Factory code: 2208906.26) with the magnetic base from the product Sirio SKA 900 1/4 MAG (Product code: 220713075 Factory code: 2207130.75). A 3 m long cable is included.
  6. Antenna adapter: to convert antenna to SMA connection Keple FME Male to SMA Male Adapter.
  7. Duct-tape to stick the antenna cable down where needed.

Build steps:

  1. From the parts listed above in item 5 & 6, put the antenna together from the two Sirio products. You will have some parts left over, but those can be added to your radio equipment reservoir.
  2. The car luckily has a sufficiently large gap by the upper hinge to let the cable pass even when the boot is closed.

    3. Antenna cable passes into car via gap by hinge. Antenna cable passes passes into car.
  3. The 3 m cable (that came with the antenna) is passed down to the base of the boot by running it down the outside of the car frame that lies underneath the boot lid; and then into the boot and upwards, inside the boot, to the compartment under the roof. Use the duct-tape as required to make the cable run correctly. Doing this long run means that the water-proofing sealing that seals the lid is only compressed, when the boot lid is shut, at a location down low at the base of the boot, and so at a location where water will not come in as a result of the seal being a bit compressed there.
    4. Cable goes down outside the boot lid and into the car at the bottom of the lid.
  4. Put the rnode into the boot's roof comparment.
    5. The rdnoe in the compartment under the roof in the boot.
  5. Connect the antenna to the rndoe.
  6. Connect up the power supply to the rndoe (only if antenna already connected, so avoid damage to radio).

Using the car rnode:

  1. The rnode will run as long as the UPS is sufficiently charged. It seems that running the car for about an hour a day is sufficient to keep the rnode on 24 hours. That way the rnode is up and running mostly 24/7. If a manual re-start of the rnode is required, this is easy to do with the button on the front of the Geekworm case.
  2. I had this setup on the car for over a year with no problems. In underground car-parks of height less that 2.10 m the antenna just flips over and you can put it back up straight when outside again. The antenna holds fast at all driving speeds I have tried. For the car-wash, the antenna has to be un-screwed at the cable entry into the magnetic base.
  3. The long cable to the antenna was never a problem at all for when I was using this with a Station G2 node under Meshtastic for over a year, and I got one message over 100 km with that setup. The cable appears to be of sufficient quality that the radio appears to work well enough.
  4. The MeshChat settings for a car rnode are probably better set to Interfaces -> three dot menu -> Optional Interface Settings -> Roaming, but this is a matter for testing.
  5. There is a bit of a disco feeling in the compartment.
    6. Red blue and green lights on the rnode, with the slots of the case making red stripes on the roof of the car compartment. Red blue and green lights on the rnode, with the slots of the case making red and blue stripes on the roof of the car compartment.
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Last edit 03-30-2025 MMDDYYY 12:00:00 EST

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