Public Lab Research note

3D Thermal Plume Fishing Bob

by kgrevera | July 22, 2015 00:00 22 Jul 00:00 | #12087 | #12087

3D Thermal Plume Fishing Bob


Sara Wylie and I are collaborating on a project to further develop the thermal fishing bob design. We explored a number of possibilities at our workshop. This is one of the ideas we brainstormed. Our goal for this project is to design a thermal fishing bob that can really show us the gradient of temperatures throughout the thermal plume. An obvious issue with the thermal fishing bob is that it only have one thermistor and one LED so we only get a 2D image of a 3D phenomenon. So, we are working on a design that will allow us to see more of the thermal plume.

Research Questions

  • What is the best way to wire the series of LEDs?
  • What is the best way to keep the LEDs from getting wet?
  • How do I keep the LEDs visible but still protect them from the water?
  • How do I waterproof the thermistors?
  • How do I keep the rig afloat?


This idea piggybacks of of Laura's multiple input fishing bob concept, but attempts to solve he problem of not enough inputs by using an Arduino Mega instead of an Uno and of course changes around the standard thermal fishing bob housing. The first concept I came up with was a series of thermal fishing bobs attached to a long stick of bamboo with their thermistors hanging down into the water. Obviously this was a rough design, but Sara Wylie had an idea to improve on it. Her idea was to house the LED's inside a clear plastic pipe which would be above the water and the thermistors below. This pipe would be se upright in a towable rig, like the pool floatie rig so that it could be pulled behind a kayak. A second idea was to build a chain of 3 color LED's by soldering them on to long wires. This idea was based on a concept I saw on Instructables.


  • Arduino Mega
  • Thermal Fishing Bob
  • pool floatie
  • clear pipe
  • 3 LED's
  • 3 thermistors of varying lengths



Rough first concept


Rough second concept of LED chain


Sara Wylie's edit


Sara Wylie's edit with thermal gradient illustrated


I've been slowly building a "buoyancy-driven underwater glider" robot, as an extension of the thermal fishing bob concept. It now has a dedicated research page if anyone is interested- My goal is to use it as a platform for various open-water tools in development incl. RIFFLE and the Thermal Fishing Bob.

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