From: Sean Breheny <shb7@cornell.edu>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Sun, 19 Jan 2020 18:21:20 -0800
Subject: Re: [EE]:: What do you wish you had known before you started with
	Electronics.
Thread-Topic: [EE]:: What do you wish you had known before you started with
	Electronics.
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I finally looked up the type of hot melt adhesive which I use. It was
called PAM UX8012 when I bought a large supply in 2013. It seems now that
it is made by a different company which bought out PAM - FastenMaster
FLEX40. It is intended for use in flooring (mainly adhering flooring tiles
and carpet to concrete and wood). Typical hot melt glue is ethylene-vinyl
acetate copolymer (EVA). This stuff is a mixture of ethylene-ethyl acrylate
(EEA) and ethylene-butyl acrylate (EBA) from what I can tell.

On Fri, Jan 17, 2020 at 2:43 PM Sean Breheny <shb7@cornell.edu> wrote:

> I've had much better luck with hot glue than Russell ;)
>
> I use certain higher-quality (supposedly) glue sticks which melt at a
> higher temp and have a very distinctive odor (I don't have the brand
> handy). If I am bonding to plastic or wood and the surfaces are clean, I
> have some projects which have used it 10 years ago and are still holding
> fine. Used only for moderately structural stuff at no more than maybe 2 p=
si
> (7kPa) tension or shear - no strong "peeling" moments.
>
> On Thu, Jan 16, 2020, 4:28 PM RussellMc <apptechnz@gmail.com wrote:
>
>> We have had discussions like this long ago (I think).
>> I'll post this and see if there is any interest in an updated ramble. It
>> might lead to a worthwhile summary. Or not. TBD.
>>
>> In January 2012 I answered a Stack Exchange question "What do you wish y=
ou
>> had known before you started with Microcontrollers?"
>> My answer was intentionally more along the line of  "What do you wish yo=
u
>> had known before you started with Electronics."
>>
>> For reasons disparate the Q&A was locked long ago, which I think is a
>> shame, as the subject is useful.
>> My now locked answer is here:
>> https://electronics.stackexchange.com/a/25294/3288
>> I've copy & pasted my answer below. Formatting has been 'altered'.
>>
>> Lines [in square brackets] have been added just now.
>>
>> Much more could be said :-).
>>
>>          Russell
>>
>> _____________________________________________________
>>
>> RS232 is upside down
>>
>> [Logic 0 is negative wrt ground]
>>
>> Most of everything you will have problems with will be caused by "bounda=
ry
>> conditions" - stuff that happens as things get going or start stopping.
>>
>> Always initialise your variables. ALWAYS.
>> And your interrupt vectors.
>>
>> Little endian.
>> Big endian.
>> High/low byte first.
>> Left adjust N bits.
>>
>> Flags left still set when work is done (eg IRQ flags).
>>
>> Stack overf
>> ck underflow.
>>
>> RTS versus RTI
>>
>> Watchdog what ?
>>
>> Simple interrupt driven timer real time round robin scheduler that looks
>> like a full RTOS but can be understood and written as you go. Trivial an=
d
>> amazing.
>>
>> Microcontroller pin specs - Vout / Iout relationships. Vin limits. Holdi=
ng
>> pins near mid rail.
>>
>> Always define all pin states under all conditions.
>>
>> Thermal resistance.
>>
>> NEVER let a body diode conduct (or mayhap a few uA if you really really
>> must) that your life shall be long on the face of the land - even when t=
he
>> great satans come and tell you it will be alright and that you CAN safel=
y
>> use them for input clamping.
>> [Even when eg Microchip application notes use body diodes for clamping
>> high
>> high impedance mains inputs, believe them you musn't. Court the dark sid=
e
>> do not]
>>
>> Absolute parameters and operating parameters in data sheets mean totally
>> different things and must NEVER be used interchangeably (or at least not
>> the former for the latter) that your days may be long ... etc.
>> ["Typical minimum" does NOT mean "minimum" allowable and may mean
>> different
>> things in different cases.
>> eg LM741 [RIP] typical min operating voltage  is shown as +/-12V. It can
>> legitimately be run on loweer without violating specifications. How much
>> lower may be hard to tell]
>>
>> V =3D I x R. The V doesn't happen if the I isn't happening so drawing
>> conclusions re V without I is pointless, or worse.
>>
>> Hex Schmitt inverters !!!! God's gift to DIY digital AND analog
>> electronics. (74xx14, CD40106, ...).
>>
>> CMOS logic !!!
>>
>> Opamp common mode range.
>>
>> Opamp output headroom - high and low.
>>
>> [Opamp Vout drives to "almost ground" - implications, solutions, problem=
s,
>> ...]
>>
>> Voltage regulator dropout - ON TOP OF Vout min.
>>
>> Voltage regulator Iout min when relevant.
>>
>> Lead acid battery sulfation. Don't let it !!!
>> [V_bat-la >=3D 12.6V ALWAYS]
>>
>> The utter magic of LiIon batteries, despite their drawbacks.
>>
>> The utter nasty chicaneries of NimH batteries, despite their nicenesses.
>>
>> [The benign loveliness of LiFePO4, mostly.]
>>
>> [Battery chemistry-very-variable temperature limits, high and low, charg=
e
>> and discharge, performance when near limits, work arounds, do not work
>> arounds].
>>
>> LSD NimH (no, not lysergic ...)
>>
>> Adjustable current limit adjustable voltage power supplies for prototype
>> life maintenance.
>>
>> MOSFETS !!!!!!!!!!!!!!!!!!! Yee ha
>>
>> Low Vgsth MOFETS and digital electronics and large loads. Yee Ha.
>>
>> MOSFET, 2-jellybean-transistor gate drivers.
>> Why you NEED a gate driver.
>>
>> Tantalum capacitors die die die !!! (and they do)
>>
>> Input leakage current. What's that?
>> Input off what ?
>>
>> Accuracy / resolution / linearity / monotonicity / ...
>>
>> Isochronous.
>> Asynchronous?
>> No, Isochronous.
>>
>> [Clock stability crystal / ceramic / RC / ...]
>> [Aging. Worst case. Across range. Cumulative. ...]
>>
>> Asynchronous. 1 bit, 2 bit, 1.5 bit, more.
>> LSB first!. First? YES! Start bit, stop bit, parity bit, forced parity, =
no
>> parity, do you know if parity is on?
>> Bit sampling - middle of bit, samples per bit.
>> [Accuracy with RC - absolute error per end, shared drift (temperature),
>> resonator, crystal internal clock - old one and new.]
>> Always more !!!
>>
>> Crystals shatter on high g./ Or just drift and jump.
>> Or shatter.
>> [Crystals shatter on high drive. Not so much an issue with IC driven clo=
ck
>> circuits.]
>>
>> Hot melt glue fails. Always. Always ? *Always *! Weeks to months to just
>> maybe years.
>> [If you MUST use hot-melt glue with aims of long term retention, it MUST
>> be
>> mechanically locked through holes or slots s that when the bond fails th=
e
>> part is retained. This is a very poor system - but the best you can
>> manage].
>>
>> Acid cure silicone rubber is a no no no no.
>> [Neutral cure SR - very very useful]
>> [AlkOxy "neutral cure] is cheaper than full neutral cure but is corrosiv=
e
>> to bare copper (but not much else].
>> Thermally or electrically conductive epoxy is filled with X - you can fi=
ll
>> it too.
>>
>> Silicone rubber and cornflower say 50-50 to start. Try it, you'll like i=
t.
>>
>> Heating a large pottle of fibreglass resin on a cold morning may make it
>> go
>> off faster but THAT fast ??? !!!!
>>
>> Tin whiskers.
>>
>> If they say ROHS their magic machine will spot your non compliance
>> instantly.
>>
>> Learn to solder. Well.
>> Note that solderability can vary very very greatly.
>> Bad solder is a waste of calories and not worth sharing your life with.
>> ALWAYS clean / abrade a bare board that has sat around a while before
>> soldering - time and stress saved can be monumental.
>> Learn to NOT catch falling soldering irons.
>> Learn to kick falling soldering irons while grabbing their cords, if the=
y
>> have one.
>> Learn not to drop soldering irons.
>>
>> Nd2Fe14B (and similar "rare earth") magnets are great fun BUT -
>> They can do you a very serious injury.
>> A good one can take out a wallet of magnetic cards at a single bound. Th=
ey
>> shatter chip and break with ease.
>> The US process ones are significantly inferior in field strength to the
>> Japanese process ones.
>> Provide up to about 0.5 Tesla across an airgap of about half material
>> thickness.
>> Magnetic field drops as inverse SQUARE of distance from one pole but two
>> poles are always involved so it looks like 1/d^3 at a distance.
>> [They corrode with time - fast enough to merit providing some sort of
>> conformal coating in environmentally adverse conditions. This is probabl=
y
>> usually due to breaks in the plated surface. Handle accordingly.]
>>
>> Much more ... :-)
>> --
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>>
>
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