BioBoard/Equipment

Sensors

We need to decide whether to build them ourselves or whether to buy them ready-made and just worry about assembling the bits and making everything communicate. Important considerations would be affordability, accessibility and required precision.

Thermometer

Commercial thermocouples are available from approx. $20 upwards

• Hollow Tube Thermocouple Probe $19

There is also a somewhat sketchy Instructable for how to build one - at approx. $15, it’s not going to be much cheaper, though, so choosing the DIY version would be mostly for the educational benefit of actually building it (almost) from scratch.

Presently have a prototype thermometer which uses a one-wire device: DS18B20 digital temperature sensor - it's not talking to my Arduino yet, but it will. Oh, yes...it will. (Rikke)

pH-meter

Maybe we can buy one of these (or similar), break them open and figure out how to read the output from an arduino:

• HANNA Instruments HI 98103 $55
• Milwaukee pH600 $20 - doesn't look like it needs specific buffers for calibration, but the accuracy is probably not great. Maybe it's enough, though.
• Google shopping results approx. $40 upwards
• SOTA pH Electrode $100 - expensive, but so so sweet: designed for continuous measurement, and comes with any kind of connector.

You can also get little tester units, such as this Jenco 610 pH tester for $30 - perhaps it could be hacked?

There’s also the option of attempting to build one ourselves using this (or a similar) schematic with the Arduino instead of a voltmeter - not necessarily cheaper, although it’d certainly be both fun and informative.

Dissolved oxygen (DO) probes

• DO-BTA Dissolved Oxygen Sensor $209 - cheapest commercial product I could find. In this case, it seems relatively safe to assume that bulding one ourselves would be cheaper.

Potential DIY designs and progress

• Mod an automotive O2 sensor to make it a membrane electrode - New sensors for out of date cars are available on eBay for $10. Although these sensors typically operate at ~300C (won't work for us), they do have the required platinum, anodes, and teflon membrane. I'm thinking I can knock out the zirconium matrix and add a KCl electrolyte and see if we can get a reaction started at room temp (fingers crossed).
  • Progress thus far: Ordered 3 $6-$10 probes on ebay to futz with

• Build an intensity or time based optode from scratch - Recently, people have been using a ruthenium complex as a visual (fluorescent) indicator of oxygen concentration. This complex is excited by a blue LED, then its transmission is measured by a filtered photoresistor (more details here in pdf). There could be some serious tecnical hurdles to overcome on this one, but if it works, this would be a way better sensor in the long run - no calibration needed, all solid state (super low maintenance). The Rh complex is expensive (~$70/mg), but could probably be used for quite a few electrodes.

Living biomass

This is still an open question on all fronts. Don’t know how much such a sensor would cost, if we’d be able to hack one, and whether building one ourselves is actually a real option.

Controller and data transmission

Is Arduino going to be our platform?

Here's a possible design: An arduino hooked up to a bunch of different probes and in turn hooked up to either an ether/wifi shield or a full linux box (I've previously used the excellent and tiny 1 watt biffer board in this manner). As data comes in it should be timestamped, categorized (pH, temperature, etc) and sent (via shield or pc) to a server somewhere on the internet using e.g. JSON over HTTP post. The server would run a custom web app (e.g. Rails) that receives data, logs it to a database and generates graphs on demand. Add a Comet server and the graphs could be live-updated as the data comes in. We could add features that lets new users sign up and get a unique key which they use when transmitting their own data to the JSON web service on our server. The server then uses the key to associate the data with the user, and the user can look at their graphs and share them with others. We can implement the "export to CSV" on the server side, allowing users to analyze the data using the tool of their choice. If we put all of the code on github, then others can easily fork the code and add their own features. To me, the hardest part of this project will be finding/building cheap measurement probes that are accurate enough (how accurate is enough?) and require little or no calibration. - (Juul)

Sensor data collection

Which board would be optimal for our purposes? Does this depend on the sensors?

Wireless data transmission

How? Immediate suggestion would be ethernet shield, but others options are available and perhaps preferable.

Data logging and visualization

Log

Data should be recorded at regular intervals; ‘smoothing’ by logging average values over each interval rather than point values may also be an option. Export to a simple spread sheet arranged to make later data analysis and visualization easy - how to do this?

I suggest that we use a simple data serialization format like JSON for logging the data, and then include an "export to CSV" function where you can select the data you want exported (pH, temperature, etc). This should allow people to use a variety of programming languages and data analysis tools without a lot of work on their part or ours - (Juul).

Graphic visualization

It would be awesome to have the visuals built in from the beginning, as good graphics will greatly increase people's understanding of the correlations between the factors we measure.

Website

A virtual space for the collaboration, organization and publication of the project. So far, this wiki seems to work well for our collaboration and organization purposes, but it may not be the best platform for presenting, sharing and comparing data?

I could do a quick Rails site with some live graphing and throw the code on github. We could keep it really simple for the first version, but encourage people to add functionality for collaboration. - (Juul)