[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Attendance, Groups, Purchase Advance, Motors, Parts Stock and Pancakes
Attend both your primary and secondary lab period for the entire
period. (in a week without Option Talks)
During the Option Talk Week students must come either
Tuesday 8-12 or Thursday 3-7 (student's choice)*.
Parts shopping must NOT be done during the lab period.
(regardless of what the Drs Morison, Davis or Youle may
have mistakenly said.)
Your scheduled lab periods are not the time for extended
"breaks", meals, or other activities.**
(regardless of what the Drs Morison, Davis or Youle may
have mistakenly said.)
*Believing most students would 1) prefer not to get up
early, 2) prefer to be marked 2 days later, I would
anticipate the natural distribution will be few students
will come Tuesday and a number that cannot be accomodated
by the lab will come Thursday.
I recommend students come Tuesday 8-12 --- if more than
half the class is there, you can always come back Thursday.
Half the class is 24 groups, which, with one group per station,
will just fill the larger lab.
**A break is a few minutes after many minutes of intense/
stressful/precise/delicate work. There is no set number or
time for breaks in a 3 hour period, it will depend on the
nature of the work you are taking a break from. Breaks
punctuate productive work as needed to maintain alertness
Of all of the changes that have been identified as possible, only
a small number are known for sure; the outcome of the others is as
yet unknown. No group changes will be announced in this e-mail.
If you have found out you are on probation (avg <60%) and have
decided to stay in EngSci, please e-mail me to this effect.
The purchase advance web stuff has now been created. As soon
as there are parts that can be bought (our parts stock is low
right now) students may begin buying OOPS (replacement, wrong
track, emergency) parts from the lab. Students are encouraged
to continue doing their own primary parts shopping.
I have noticed many groups purchasing very powerful, sometimes
very expensive, ungeared DC motors. The DC motors that
run the CANADARM heaving around tonnes in space are SMALLER
(they are about the size of a tomato paste can) and less powerful
than many groups have selected to travel across smooth floors at <1m/s.
This is fine, if you can control those motors. The motors in my
Tag Robot are quite large and ungeared, run at half voltage, with
small wheels. Many groups in the past have used such motors and
constructed gear boxes, about half having the manual skills necessary
to successfully construct a working gearbox.
The far better option is to BUY GEARHEAD MOTORS, that is
ones with an integrated gear box. A good gearhead motor, with a
motor about 3cm long and 2cm in diameter will be quite sufficient
for drive motors even on a tag playing robot. If you are having
any trouble building your gearbox, controlling the motor's
excessive power or supplying its excessive current draw, please
look now for a pair of small gearhead motors.
If you buy a gearhead DC motor, test it in the store (the nice
man in the basement of surplus will do this) and estimate its
turning rate. 300rpm is 5/s which is about as fast as you can
count silently. This with a 6.4cm dia wheel is 1m/s. If it turns
at a rate even twice as fast, this can be taken care of with a
smaller wheel and or lower drive voltage. If it turns more
slowly than this, a larger wheel or a low speed o-ring belt/pull
system can compensate or you can just move more slowly in a more
The parts stock is in extremely short supply on marginally suitable
gearhead motors, and most were purchased from the US and therefore
about $15 each. If you cannot find a suitable gearhead motor, I
will make some available from the lab during Option Talk Week.
I have now identified the amount of money I have to spend expanding
the parts stock. Realistically, as long as the TA strike lasts
(and for a week or more after it ends), I will not have the time to
do any extensive parts shopping. So, in an effort to make sure there
is a part stock, and that the stock is useful to you in times of
emergency, I have a proposal. Students may purchase some of the
parts for the parts stock and I will reimburse the student in cash
for the parts. I still reserve the right to elect not to purchase
parts from a student for any number of reasons but here are some
guidelines that will help avoid that situation:
ALWAYS GET A RECEIPT --- I can't reimburse without a receipt.
ALWAYS GET AN ITEMIZED RECEIPT --- Surplus is famous for their
receipts that say only "Parts". It need not be exact but at
least get them to separate them into big chips by name, small
logic chips by count, opamps by count, transistors and regulators
by count, capacitors by type (i.e. coke-can sized electrolytics
counted separately from tantalums) and count, similarly with
switches, relays, connectors, etc.
Except: when I have asked you to get a specific list of parts
from a particular store and say otherwise.
BUY ONLY PARTS STOCK PARTS ON ONE RECEIPT --- I don't take
partial receipts. If you bought 4 and need 2, (observing
all guidelines below) I may do the following: Reimburse for 4,
take the entire receipt, and you then purchase 2 from your
Purchase Advance Account. Try to avoid this shuffle if possible
by just putting the parts on a separate receipt.
Purchase Under These Conditions:
b) When I see you have a particularly useful part, I may ask
you to get a certain number more at that store on your next
c) When you would like to make a significant purchase (totalling
>$20) you e-mail me to get approval. For instance, we do need a
limitted stock of emergency components for the one 68HC11 board
everyone has purchased but I do not want 5 people all buying the
lab spares, that is too many.
d) When you see some parts in a store that are particularly useful,
and it would amount to a significant purchase (>$20), call
me and speak to me before you buy: 667-7942 in the mornings well
before lab time, 978-3130 near or during (your non-scheduled)
f) You may buy parts for the stock without contacting me first if:
- it is a small quantity and cheap,
- everyone is using them,
- you could accept me electing not to buy them from you,
- they are a failable item that might need emergency
- they are a rare item at a good price.
e) Make sure you only buy things that many people might need.
f) NEVER BUY:
- unmounted gears, batteries, wire, nuts and bolts, chips
not referred to in the manual, solar cells,....
- from Active Electronics or any other non-surplus store
unless absolutely necessary, (i.e. for certain HC11 parts,
opto-electronic parts, sensors etc.)
** ALWAYS buy working surplus from surplus stores.
g) Buy scrap Lexan from Cadillac Plastics only, (at $1.00 per
pound) and in flat, simple rectangular geometries of >1/8 inch
thickness, >200 square centimeters in area, or rods >3/8 inch
dia and >15cm long. (I use Imperial where that is the
dimensions it is constructed in, Metric where you estimate.)
h) Buy Gearhead DC motors rated at or useful at 12V or less in
multiples of 2 motors only, and never for more than $10 each.
Please do not buy car power-window motors for the lab, though
these can be useful in your projects.
i) We are currently short on:
Regulators 1A, T0-220 package, +/-5V, +/-12V, +/-15V
Tantalum dip caps .1microF to 47microF >16V (tear drop-shapped)
Epoxy dip caps 100pF-.1microF (yellow/blue, pillow-shaped)
Military Monolythic 20pF-.01microF
(1x4x4mm, sharp-edged-block shaped)
Most logic chips,
Simple Quad Opamps like 324, TL084
Good Gearhead motors rated at or useful at <=12V,
<300rpm output, <1A, that you can close one hand around
j) To the junior Brian Costellos out there, this is not a
scam to pump cash from your credit card to your pocket,
to deplete your Purchase Advance Account prematurely,
pump up your RRSP, get free life insurance or whatever.
I made pancakes again this morning and took some data. First, here
is the recipe, should you wish to repeat the experiment to observe
batter consistancy and results.
In a 2 liter mixing bowl, the following was placed:
1 large egg
1 coffee cup of butter milk
1/2 coffee cup of 2% milk
2 proper tablespoons of sunflower oil
1 proper tablespoon of sugar
This was beaten with a whip for 5-10s. Added to a flour
sifter were to following:
1 coffee cup of all-purpose white flour
3 proper teaspoons of baking powder (not soda)
1/2 proper teaspoons of table salt
A spoon was used to gentle stir the dry ingredients of the sifter
to eliminate the layering.
This was sifted onto the entire surface of the liquids to a depth of
2-3mm. The bowl was then mixed with about 4-8 strokes of the whip
and then more was sifted onto the surface. This was repeated until
the contents of the sifter were exhausted.
One new 18cm no-stick frying pan was used on a small stove element.
The element was preheated at 6.5, then reduced to 5.5 and then finally
to 5 at steady state.
Batter was poured on the center of the pan to create 10cm diameter
pancakes. The whip was used to make the pancake have a uniform
thickness. The depth of the batter was about 5-6mm.
The pancake was cooked for 50-60s on the first side. At this
point the second side was bubbled through but still liquidy.
The pancake was flipped and cooked on the second side for 45-50s.
(Different times were attempted for different pancakes, the
range indicates best results.)
By listening closely, over the din of children, I heard the power
cycling of the element in steady state and recorded transitions at
the following times in seconds: 12,18,25,32,38,46,53,59 and 7,13,21,
29,35,42,49. I believe I was hearing both the turn on and turn off
transitions as the element expanded and contracted under the pan
making a series of ticking noises. The series of ticks were about
3-4/s and lasted over 3-4s. Timing was done from the first tick
in a burst. Since my watch is a jump-second hand and because I
may not have heard the first few clicks over a crash or yell, I
estimate the error to be +/- 1s.
My wife said these were the best pancakes I had ever made, which is
not saying much I guess considering the only way I could talk her
into letting me do it was to say it was necessary as an experiment.
Making good pancakes is hard. I still predict, though hard, making
pancakes under machine control is doable.
Make small pancakes. Concentrate on making an edible if not
visually appealing product. Set aside at least a week of testing
with a fully integrated machine adjusting parameters to achieve
an edible result. Don't worry if your machine's first 20 attempts
produce an inedible result, it can't be as bad as the one I made
this morning where my plastic spatula melted into it and stuck to
the bottom of the pan necessitating a new smaller pan. Use a
new pan --- be ready to replace your cooking surface if it gets
damaged from overheating.