nuckolls.bob(at)aeroelect Guest
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Posted: Sat Feb 26, 2011 7:39 pm Post subject: Turning simple-ideas into working hardware. |
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At 06:35 PM 2/26/2011, you wrote:
Well, I certainly appreciate and respect your opinion ( I wouldn't
have asked if I didn't). And, you are right concerning having a solid
project that has been put through the paces prior to having the kids
get frustrated with it. I can tell you I am a bit frustrated as a new
electronics teacher ( have been teaching Intro classes for 2 years).
The curriculum I have developed (as mentioned) includes building a
crystal radio and this has been quite successful.
Great!
We then build a simple amplifier which uses an LM386 along with
resistors and caps on a perf board. This has turned out to be a good
conclusion to that class.
Another good one.
My frustration comes in trying to advance a bit into a project that
will be a step up in challenging skill levels and not blowing them
out of the water.
That is where the artful side of teaching must prevail.
We are also financially limited due to a $15 cap on what we can
charge for a lab fee, so as far as kits go...there are a bunch out
there but out of the dollar range. This forces me to find circuits
that I can purchase the parts and keep things cost effective. I
suppose I can keep things simple with bread boards and timing
circuits, but I am open to suggestions for projects if you have any
in your bag of tricks. My bag is just beginning to grow along with my
experience. Thanks for testing that circuit! Back to the drawing board.
I'm pleased that you've already got a general
notion for what the path to success looks like.
I've had several teachers approach me who were
looking to launch their first endeavor. There
the challenge was greater . . . I had to teach
the teacher. You've worked past those early
hurdles and can focus on refinement.
Some years ago I was working with a teacher who
wanted to go the next step above a crystal set
but with some attention to history too. How about
a one-tube radio? Most folks don't know what
tubes are. But they're a whole lot easier to teach
than transistors! Further more, you can take one
apart and hold the pieces in your hand. No such
luck with a 2N2222.
One of the ideas that grew out of our discussions
was the development of a one-tube radio module.
As with the crystal set, the major performance driver
was the 'front end' work. It all happened with the
tuner. Further, risks to success were based more on
techniques (soldering fragile little gizmos together)
and parts selection (being able to duplicate or artfully
substitute a bill of materials).
So how about starting with a 'stock' module that
reduced the risks while evaluating performance gains
demonstrated by the student work-product.
I came up with this proposal:
http://www.aeroelectric.com/Catalog/AEC/9050/9050-600a.pdf
The idea was that these modules would belong to the
school and be re-usable from one class to the next.
The goal was to go through the now 'ancient' texts
on DIY radios and duplicate some of the tuner
designs. Then evaluate performance for selectivity
and sensitivity using some calibrated test equipment
(also built by the teacher or an advanced student).
This reduced the class-to-class costs dramatically
and reduced risks for no-learning-events driven
by assembly and/or parts selection snafus.
We thought that I would kit the modules and
he would have some of the more advanced students
build them.
That teacher got laid off and I've not heard from
him again. That was about 4 years ago.
How would you proposed to introduce and teach ECB
fabrication? There's a free ECB design package
that is VERY powerful. I use it all the time for
my projects. When the work product needs to be
converted to useable hardware, their prices are
quite reasonable and they're quick 1 day turn with
two day UPS delivery of finished boards.
http://expresspcb.com
This same package could be used for a paper design task.
Students could lay out boards, print the artwork
and swap it with other teams for proofing. This is
exactly the way we did boards at Electro-Mech and
Beech for about 30 years. For a class, three
or four teams could do layouts. Swap between
teams for proofing. Then vote on the best looking
layout and order that one for the class project
to move forward. Alternatively, you could have a
'stock' ECB that had been previously ordered in
quantity to get the cost down.
I wouldn't give up on the metal detector. But
I think it wise to have a working model
in class on Day One. Throw a schematic up on the
screen and dissect the simple-ideas. Again,
packaging, coil winding, and mechanical fabrication
presents some challenges that could blow a perfectly
good lesson plan out of the water.
Let's talk about ways to refine the metal detector
(or any other circuit) into a teaching tool. How many
students are in the typical class?
Bob . . .
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