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Data logging in a home-brew wind tunnel

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Data logging in a home-brew wind tunnel

Postby Simon Morden » Tue Jul 08, 2008 9:11 am

Hello!

I'm part of a team that's one of the finalists in the Rolls Royce schools Science prize: we're building a wind tunnel, and I seem to be in charge of the instrument package. My background is as a post-doc geophysicist, so I've no fear of the technical aspects...

The idea is to take top-end Primary age children through the whole design process for building a wind turbine - how blade number/shape affects power output, different efficiencies at different wind speeds etc, and then hopefully build a good size version using the data they've obtained for testing outside in the real world.

The measurements we want to take in the tunnel for now are:

Wind speed (actually air flow, but we can scale this). We're not quite sure which instrument to use to measure this - pitots are as expensive as you like: there are thermal, ultrasonic, and rotor designs too which come with RS232 output.

Voltage/current. We'll be attaching our test turbines to a low-voltage DC motor - which may or may not involve gearing. The output will probably (hopefully!) exceed 2.5v.

Rotor speed. I had the wild idea of using a light gate, activated by an in-situ LED or laser, to indicate every time a blade passes. It might be that this will be modified to strike a silvered patch on one of the model blades.

Measurements that we would like to make in the future:

we have a wind tunnel! We'd like to use it to explore the effect of shape on drag, getting the kids to design aerodynamic cars.

also, exploring the concept of lift with wings.

I'm supposing that both of these will involve digital balances

We intend to build two tunnels, so we'd need two of everything. The budget I have for instrumentation is £500. We already have USB compatible laptops running XP in school.

Obviously, we're looking at the DrDAQ. Is there any particular reason why it wouldn't be suitable for the above applications? My primary concern at the moment is, can I disconnect the light gate from the board and stick it on the end of a sensor inside the moment, or am I looking to get my soldering iron out?
Simon Morden
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Postby picojohn » Wed Jul 09, 2008 2:21 pm

Hello Simon,

It is unclear what you mean by:

'... can I disconnect the light gate from the board and stick it on the end of a sensor inside the moment ...'?

Regards
John
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Postby Simon Morden » Wed Jul 09, 2008 2:55 pm

There's a light sensor on the body of the DrDAQ. Is it possible to disconnect this sensor from the PCB and put it somewhere else (with the signal going to the same input)?
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Postby picojohn » Fri Jul 11, 2008 1:40 pm

Hello Simon,

You could do that or, you could use the resistance input of DrDAQ with your own light sensor.

Please refer to the user guide for details (http://www.picotech.com/document/pdf/drdaq044.pdf).

John
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