Gizmos

From Seamonster

• Technical Architecture Protocol
• Sensors, Data Loggers, Sensor Specifications
• iButton Data Logger
• HOBO Data Logger
• Campbell Data Logger
• Radio Modem
• Motes, Mote Specifications, Field Motes, TinyOS
• Programmable Logic Circuits
• Slugs Microservers, Vexcel Microservers, Gen 3.2 Evaluation
• Network Plan
• Power, Computers, Code, Gizmos, More Gizmos
• Photoshop

External resources

• Nice fellow named Scott has big-time Gizmo Know-How]
• More from Scott: Building an environmental monitoring station.

Contents 1 Introduction 2 Instrument Power Switch 3 Low-power timer system 4 Mote Enclosure 5 Passive Antennae 6 Installation Strategies and Hardware

Introduction

This page of the wiki describes useful devices that support the general purpose of SEAMONSTER. Not sensors or network components but the stuff around them, the glue that enables them to function. Related: The Instrumentation page describes what instruments we need and where they go. The Gizmo Notes page contains further remarks on how gizmos work that we don't want to forget (including warnings about aberrant bahavior).

Instrument Power Switch

We need a GPIO-controlled power switch so that a mote can turn a DC-powered sensor on and off. This is easily accomplished with a little two-MOSFET circuit of the type used in the power management board we have in the microservers. The basic idea is that one MOSFET can handle whatever the power supply needs to push in terms of voltage and current and the second MOSFET turns this first one on and off based on a wimpy little 3V logic signal that is either on or off. The response time is really fast and the switch can be driven by a microprocessor pin.

Low-power timer system

Problem: Some motes will require more power than can be provided to them at installation if they run continuously. Solution: Program the mote to spend most of its time in sleep mode (drawing micro-amps of current.)

Supposing that the mote (or other device) must further be moderated in its duty cycle and the above solution is not available; then what we'd do is determine how long the device can run on a given power supply, divide this into the deployment period to obtain a duty cycle, and express this as intervals M-sleep and N-active minutes long (say) to repeat until the batteries die.

Ideally we want to adopt the "e" rule where we provide 2.7 times more energy than we believe will be needed. This will give us some headroom, for example so that we can occasionally send queries to motes that put them into an intense data acquisition mode without breaking the bank.

Similar in execution to the previous item, this gizmo is a simple extension of the Gen 3 power conditioning subsytem board: A low-power dead-simple microcontroller runs off independent batteries suitable to keep it running for the deployment period. The micro sleeps at microwatts, wakes up every N hours, turns on a separate power supply (attached to a mote etcetera), waits for M minutes, then turns the mote supply off and goes back to sleep. The micro also reads a line from the mote which when Hi means 'DONT TURN ME OFF'. Everything else is the mote's problem.

Mote Enclosure

We need a casing for a mote that is NEMA spec and that has decent radio-wave transparency or better an external antenna. For a rough draft knockoff we bought a couple ringy-dingy plastic cases with cheesy rubber seal rings.

Passive Antennae

This is a new and truly strange idea: Placing pieces of metal (no power) on hilltops to act as waveguides and redirect radio waves over the hill to destinations that are not in the line-of-sight of the transmitter. Larry Brewster (Microsoft RF engineer, pictured below) assures us this is possible but considering the smile on his face we'll believe it when we see it.

Installation Strategies and Hardware

This is the sort of issue where an intern would be helpful: We need reliable installation strategies and hardware for each type of substrate:

Creekside       Wet, partially or fully submerged, feed to antenna off the ground.
                Will receive meters of snow over the winter.
Cairn Peak      Rocky substrate, high winds, wind chill, blowing snow, rime.
                Also applies to repeaters on ridges overlooking the water shed.
Lakeside        Similar to creekside but particular to pressure transducers and
                other lake instruments
Glacier-snow    Installed in diggable snow that will undergo melting and precip in
                the summer and snow precip accumulation in the winter; burial.
Glacier-ice     Both on Mendenhall and the toe of Lemon we have bare ice and 
                probably will need to use a steam drill. 
Forest          How to quickly, safely, and easily get an installation up in a tree.
...............
Mote General    How to establish wireless communication while installing a mote subnet.
Microserver     As for motes.