Author Archives: Kirk

Range testing xbee SX868

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Two xbee SX868 modules – with mostly line of sight and a nice 3G antenna at the other end – I obtained a safe 1km range – going up to this 1.5km if a few errors can be tollerated (showing -94 dBm). Over wet an slightly frozen ground I got -95dBm at 1km. I did get a few packets at 2km but it was showing -96 to -100dBm (very weak). This gives us confidence to install GPS units up to 1km away from their base station in Iceland. 1km

update on our next generation ice tracker

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Thanks to a lot of work by students over the past year we are on track to producing our new u-blox based trackers for Iceland this summer

Our new choice of microcontroller board running Circuitpython – it is connected to the GPS, its radio The processor is a 120MHz ARM Cortex-M4F. Basicall it has lots of ways to connect to other hardware and is pretty fast – while using very little power.
The dGPS board by Sparkfun allows us to take measurements within about 30-50s, accurate to about 2cm. They use 1/10th of the power of our previous units so our batteries can be smaller.
This is the SWARM sat-coms board by Sparkfun – allowing data communications to the web from anywhere on the planet! We will test this from a base station to shjow that the system can work anywhere and send data back to researchers daily.

Fjallsjokull timelapse camera 2022

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We installed a Browning HP4 camera on the Fjalls base station pole to test it as a way of getting a long sequence of timelapse images. It has their solar panel fitted (small one half way up) – and is filled with lithium AA batteries.

The camera will take a couple of photos after sunrise and before sunset – it is very restrictive on timelapse unlike the Brinno cameras.

older camera left in summer 2021 looking at the Fjalls lake from near the footpath

Fjallsarlon time-lapse camera

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To see if a time-lapse camera would be useful in measuing rough lake depth changes we installed a Brinno again in 2022. It is set to take one photo every day at noon.

2022 Brinno TCC200 camera looking out across the lake (including measured rocks).

DJI Zenmuse P1 camera quality test

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If you zoom into JPEG images from the Zenmuse P1 camera they look “damaged” so I took a view from a stationary (on a table) Matrice300 in jpg and raw. Converted the raw simply to tiff, cropped both to look at a small area in focus:

original image (reduced from 8192×5460 for this page)
crop from raw image
crop from JPG file showing over-sharpenning and contrast enhancement

The conclusion is capture RAW only on the P1 and batch convert later. Each raw is 86MB rather than 5-7 MB (which was suspiciously compressed for such a high resolution image) so you will need 10x the SD card space/disk space.

Swarm pico-sat coms tests

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We have been doing more tests on the Swarm pico-sat coms with a view to using their system in Iceland.

This graph shows the temperature measurements during 6 days – showing the solar panel charging. On average the modem used 52mA but the battery was providing more like 120mA due to the LEDs and feather board.

Swarm Sat-coms test over a week showing currents
The pass predictor showing the optimum periods for communcation

our first swarm.space network test

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Swarm have a system of tiny satellites (11x11x2.8cm) for low data rate communications anywhere on earth. This enables lower cost data access to very remote places.

The Swarm dev kit – the actual unit is the silver rectangular block

In my first test I received my message on their Dashboard within a minute (I was not timing!)

A maximum of 192 bytes can be sent on one message – which is OK for batches of sensor readings. Their cloud (“Hive”) has a RESTful API to gather the data easily. We look forward to building an environmental sensor network test with the help of the Swarm team!

Range testing new systems

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In our mountainsensing project we showed that fully standard communications could cover large areas. For that project we had to add an 868MHz transceiver to our designs. This year we are doing a lot of development with the Atmel SAMR30 based system-on-chip as it includes a sub-GHz radio and has good support in the RIOT-OS. One important thing to test was the typical range to make sure it was similar to our roughly 1km with the previous CC1120. Here is a photo of a quick test in the New Forest which achieved 1km with this set of antennas:

image of test node on trig-point