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0.706293334 feet^3
ha funny thats what my speaker is

Posted by renesis at 09:58 | permalink | 0 comments

put a speaker in a known volume, wrap it in plastic wrap or something
and then pour rice to the top
pull the speaker out
put the rice that fell out back
the difference in the container and the rice volumes is your speaker volume
so figure out the volume of that cylinder, and use that
its vented that big?
you have a 3" center pole or what?

Posted by renesis at 08:54 | permalink | 0 comments

you measure the cone at the surround and at the spider
and caclulate the volume
and measure the motors magnets and plate
and calculate the cylindrical volume
Vas is the volume of cabinet that would be equal to the suspension in terms of suspension stiffness
and i think its Sd thats the area of the cone
neither of those parameters tell you how much the driver is going to take up in the cabiney
because its an easy thing to measure yourself
i usually ignore the cone
because on a front mounted woofer, the extra volume from the speaker cutout is prob kind of close to the missing volume from the cone
so just measure the diamater and the height of the motor assembly
the magnet stack and the top and bottom plate
and subtract that from the box volume
lope1137: omg dont do that
use rice

Posted by renesis at 08:49 | permalink | 0 comments

and this is mostly a function of DC resistance, cone mass, and suspension stiffness

Posted by renesis at 07:53 | permalink | 0 comments

that inductance measurement is probably okay
it changes with frequency, something to do with one of the mechanical elements
also you have to test it with the cone fixed
so you have to figure out a way to keep it from moving
i dont think you can pull it out of the frame (destroying the speaker if you have more) and measure the voice coil alone
because the magnet and plates in the motor structure will affect it
anyway the coil inductance affects the woofers ability to do higher frequencies at similar sensitivities as its lower frequencies
it doesnt really affect the impedance at lower frequencies
the impedance characteristic that affects enclosure design the most is the resonance spike at Fs

Posted by renesis at 07:48 | permalink | 0 comments

analog, fear
air coils are big =\
because theyre speaker system parameters
its almost all marketing
those numbers existed before they even started the first prototype
inductance is to model the impedance increase above resonance
it has a lot to do with how much power it will produce at higher frequencies

Posted by renesis at 07:35 | permalink | 0 comments

thats the one that most people agree on and the only one i can really think of

Posted by renesis at 05:49 | permalink | 0 comments

madridman: they are dated
the older ones are probably more general
art of electronics is excellent
its written for non-electronics majors
pretty easy to understand but it covers a ton of stuff
then yeah the book was written for you
for just fpga or what?
theres prob more CE stuff about that than EE

Posted by renesis at 05:42 | permalink | 0 comments

madridman: prob not so much

Posted by renesis at 05:30 | permalink | 0 comments

fuck i cant believe i dont have alligator clip leads
i wish i could live in the lab at work
but be invisible 16 hours of that day
the other use for 50W irons

Posted by renesis at 05:10 | permalink | 0 comments

so whats it for
i never said lopes idea wouldnt work
i said its not simple and it has problems and it might burn china leds

Posted by renesis at 05:00 | permalink | 0 comments

kevtris: what happened with the bridge rectified LED?
as long as you dont blow the led with the reverse voltage it cant not work

Posted by renesis at 04:41 | permalink | 0 comments

but motors im not sure shit is always 180 opposed
2 diodes, cap, resistor, led
resistor, led
poor think gonna be all backwards
be neat to see what the reverse voltage on the led is

Posted by renesis at 03:47 | permalink | 0 comments

kevtris: thats how i seen it in most fans i take apart
so now rip off that awesome circuit...
ac-130u: its for better efficiency usually
the magnetics cost way more when you switch that low
kevtris: could just split them and flip one
wire it the other way

Posted by renesis at 03:42 | permalink | 0 comments

i prob have some shit
i have too much junk
it might be the magnetics in the psu

Posted by renesis at 03:37 | permalink | 0 comments

hahaha no
99% of leds are max rated at 20mA and thats why everyone calcs for 20mA
with variations in LEDs and resistors, youre prob like 10% over max doing correct calculations
siestacat: that one doesnt say =)
if youre buying LEDs for $1+ from radioshack, cant afford a DMM, have a deadline
youre basically blind, you need to be extremely conservative

Posted by renesis at 03:32 | permalink | 0 comments

whats the absolute max current say
your datasheet
for your device
no the led youre going to use
dude max brightness might be 2mA
theres a reason i use that value with random LEDs
you always see it and youre not gonna burn *any* leds
right now im assuming his shit aint going to make much voltage and the LED is chinese crap
not 99%
most of them
kevtris: i know because the system maybe cant even source enough current
so lope wants to waste half on the zener
not if he has a 1K resistor
anyway use a 100R instead of a 75R if you use lopes circuit
the different between like 15mA and 20mA is barely noticable
using things at max rating is retarded

Posted by renesis at 03:27 | permalink | 0 comments

or its just not on
you get no brightness
hi i gave you the simplest solution
so reduce the resistor
when you have an idea of what the system is capable of
no lope it is true
anything simpler than rectification, decoupling cap, and series led and resistor isnt sane
well maybe fat diode, resistor, and led directly across the coils
you dont know the fan voltage or what it can produce
$5 at horror fate tools
so yeah
you dont have enough for a multimeter
but you want to put 20mA into your LEDs by design
and this is for a project with a deadline
so follow lopes idea and maybe burn LEDs
and maybe only get it to light up when youre spinning the shit out of it
some 5mm leds are spec'd like 5mA =)

Posted by renesis at 03:22 | permalink | 0 comments

or some shit
thats the plan
he doesnt have a dmm
and this is a class project
and he prob doesnt have an unlimited number of leds haha
thats not a wide range thats prob like only on at max spinning
then not on all the other times
diode bridge, cap, resistor
faster it spins, the brighter it gets
you could use batteries to see how bright the led is supposed to be say at 10mA or 15mA
then try and adjust the resistance for that
no lopes uses a zener as a reg
so its wasteful
yes dude half the potential energy in the cap is just going to heat up the zener
its at max brightness if the fan is spinning fast enough

Posted by renesis at 03:17 | permalink | 0 comments

so its 20mA set
so hopefully thats not a cheap led
use a 100R instead of a 75R
so say the zener needs 10mA
so already youre up to 6.3V
to maybe even get to turn the thing on
add like .6V or 1.2V for however youre rectifying
so now you need 7v to turn the thing on
and i thought you said this shit does maybe 4v max
kevtris: yeah you unload a zener reg, the zener dies
you load it up too much, and the zener drops out
dropping out is usually a bad characteristic in a regulator =)
use a 1K resistor
spin the fan
if its not bright enough use a 470R
pc fan
with the control stripped, 3 phase reg across the coils

Posted by renesis at 03:12 | permalink | 0 comments

also the color matters
im assuming red because its worst case
yeah thats different
and thats even more issues
because zener regulators are on crack, ass backwards regulation curves

Posted by renesis at 03:07 | permalink | 0 comments

1K is probably about 2mA
which is a perfectly fine test current for leds
20mA is usually the absolute max rating, and you dont have a regulated supply, and you leds might be china shit
also you maybe dont have a dmm?
typically its better to start at lower, safe currents, and go up
if lopes idea is a 100 ohm resistor, and youve never spun this thing up before, and these are random leds
i dunno, if you have a handful of leds go for it

Posted by renesis at 03:02 | permalink | 0 comments

it depends how fast you can spin it

Posted by renesis at 02:40 | permalink | 0 comments

guess so
with 1K, no
without a resistor, yes
1/4w is fine
you can prob go down to maybe 470 ohms and still be pretty safe
what why
i made a crossover out of cardboard and zipties last night
just make that shit
i dunno what you mean by holder
like a pcb standoff?
something with a wiretail already?
dx is a mechanical engineer he could help you if he was here

Posted by renesis at 02:29 | permalink | 0 comments

oh thats hack
now youre going to burn the zener
get a 5W one or something
wtf @ easily
good circuit that shit shouldnt burn at all
you dont have a dmm?
just use a 1K resistor
and you just burnt your led
that seems right
you put the led in parallel with the resistor it doesnt do anything
led has to be in series
two devices in series have the same current

Posted by renesis at 02:24 | permalink | 0 comments

that section of the circuit will behave the same
1/4W 5% carbon or film is fine
( max_input_voltage - led_forward_voltage) / maximum_led_current
thats your resistor
yeah probably
you could just try a 1K resistor
to be safe
the led might burn in the first good fan spin
youll be like WOAH THATS BRIGHT YEAH YEAH YEEEEEEEEEEEAH WOOOOOOOOOOOO oh shit where did the light go
truth ^
1m wont work
the led will be fine it just wont light up

Posted by renesis at 02:19 | permalink | 0 comments

did you just throw the led across it or did you actually use a resistor
heheh just checking
it just wont be quite as bright
and it wont turn on as early
i totally got water in one of my flukes
it ate the insides =(
and siestacat
siestacat: most likely
in series with the led
yeah what lope said
yes directly in series with the led, can be before or after it
haha another fan
anything in series, nothing in parallel, you can put the parts in any order

Posted by renesis at 02:14 | permalink | 0 comments

better devices, heh
siestacat: lots of switch mode supplies use them
and yes it will matter
and wtf youre using the motor as a generator?
im not sure that works with a fan motor
anything that chops up dc voltage at higher than audio frequency
wow the fan will power its own coil switches and hall sensors i guess

Posted by renesis at 02:09 | permalink | 0 comments

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