Solar power for off-grid streaming
Benny, Rob, Franco, Grant, Pablo, Eric

This is a place to put thoughts and experiences from the Cerro Pelón stream in State of México, which is an off-grid installation with a 3G router, Pi streambox and low power custom preamps.

Our aim would be to record our calculations, tests, links and end up with a set of instructions in order to get the Cerro Pelón installation working well, and to create a resource that can be used in other locations eg in Chicago by Eric’s students

Cerro Pelón stream - microphone icon on the Locus Sonus soundmap - 18 Jan 2018 23:23 in London


Introduction

Rob Mackay took the equipment to Mexico in January 2018 and he and the team installed it at a site in the mountains within the Monarch Butterfly Biosphere Reserve at Cerro Pelón. 


Remote recordings made from UK have demonstrated that the stream can convey fine detail with a good ‘binaural’ stereo image that creates a strong sense of place.

The stream has received a lot of interest from the network of those interested in the Monarch butterfly and its remarkable migration between sites in Mexico and northern North America, which spans 4 generations.

It was possible for ornithologists  to identify various species of birds by listening remotely.


Description of the installation

Our aim has been to set up a technical proof of concept in a relatively short period of time, to demonstrate feasibility of a long term off grid stream.

The solar side has evolved as we adapted the installation. Eg we couldn’t use the 4G dongles we expected to be using (because the ISP doesn’t support them); so we added a 3/4G Huawei router, which has a quite high power consumption. We initially plannned for 2 streamboxes; but we have focused our resources and equipment on a single streambox for the time being.

Update - April 2018

In March, we installed a fully functioning off-grid system, which has run continuously in a number of weeks.
In the process of re-installing, the preamplifiers we were using developed a fault, which we are the process of trouble-shooting. This will bring the level and detail of the stream back up to its previous level.
We are currently working out how best to test and fix this part of the installation.

Components


The streambox is in a weatherproof plastic ‘dribox’ with the microphone capsules mounted with grommets in opposite walls. 

The box contains:

On the audio side:  
— a Raspberry Pi 3 with 
— Cirrus soundcard ‘hat’
— 2 x custom preamps
— noise reduction circuitry
— microphones
— audio cables

On the power side: 
— a 10Amp charge controller
—  inputs to the charge controller from solar panel(s)
—  in / outputs to /from the controller to the battery (ies);