Canford liaison

[Penri]

Hello everyone

I'm going to be away from home on Monday 5th November so will not be at the Model Town, Terry is available to be there should anyone from Canford Schools wish to visit so please let us know your plans, thanks.

Hope you all had a great half term break and are rearing to go on your projects.


Penri

[geoffhorton]

Hi - there is progress and I have asked all the boys to post here. Since this hasn't happened yet I will try to get it done on Monday. We will not be coming to the Model Town.

Ben has some 2-D plans which he needs to make into 3D extrusions for printing.
Flinn and JC were getting good spikes from their search coil and now need to turn them into square pulses (unless you advise otherwise).
Tom hasnt told me anything!
I can report good progress on the water tunnel - the tank is sealed and the final outlet is ready to fit. I expect to see water flowing next week!
I dont have a candidate for the water level sensor but will try.

[TerryJC]

Geoff,

Glad to hear about the progress and thanks for letting me know that I won't be needed tomorrow.

I'll let Penri give you the definitive answer to your comment about squaring off the pulses, but from a system point of view there are some constraints:

• The Pi will need the pulses to be approximately 3.3 V amplitude to suit the GPIO specification.
• The signal will need to have reasonable integrity when it arrives at the GPIO pins as any spikes or ringing will add to the uncertainty of the measurement. If the wires are too long then we will have to clean them up near to the Pi anyway.
• Having said that if the pulses are too sharp, then we may end up with ringing anyway, depending on the characteristic impedance of the wiring (which is difficult to define unless we design for it).

At the end of the day, Penri and I are going to have to come up with a strategy for maintaining the integrity of signals from all the sensors and the PWM signal that we will be utilising to control the main pump.

So the short answer is that there will be a global solution to this eventually (we used level shifters close to the Pi to condition the signals in the installed system with unscreened twisted pair cable to carry them).

If the boys want to clean up the signals, then I don't think we would have a problem with it. They will need them clean enough to trigger a scope presumably and that would be good enough for the moment.

The main task that we set them was to design and develop a sensor; an exercise which is mainly focussed on the techniques and the physics behind them rather than the nitty gritty detail of the system design.

[Penri]

Hello

Terry has summed it up perfectly, I’d also rather see the sensor developed and charecterised than worry overmuch about squaring the pulses, but it would be good to have some parametric data about them at different rotor speeds.

Hwyl

Penri

[geoffhorton]

thx. discussed with Flinn and JC. Looking forward to them posting their thoughts! rgds

[geoffhorton]

We have some items to discuss and propose to visit WMT if you are available. pls confirm. thx

[TerryJC]

I am. See you around 2 pm?

[Penri]

I'll be there also.

[geoffhorton]

yes - we should be there by 2. rgds

[flinntiefenthal]

Sorry about the delayed update;

At this time we have printed our waterwheel, which I believe you have seen. We fitted the bearings and the magnets into the wheel with the help from some filing and drilling. We are currently working on creating our first prototype to gather information in order to create our own specification with exact numbers. Dr Horton informed us of a water flow system that we could use to gather our data needed, however, we are unsure of the progress of this (we presumed it would be ready to use today, but we have not been informed if it is available today.

following are pictures of what we have done so far.