C
cpemma
Guest
nws wrote:
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N
nws
Guest
Can you explain why the resistor is needed. Is there a formula involved?You need to add a capacitor and a parallel resistor. I would suggest a
1 mfd cap and a 1 meg resistor, both in parallel from pin 5 to ground.
The bigger the cap, the slower the response.
Again, can you explain exactly why we need a resisitor in seris, is thereTrue average depends on a lot of factors! But to average, it should
also have a resistor in series with the diode. However, Not even sure
why he put the diode in there as its Not very good rectification and
wont't work below 0.6 volts. Ideally, It Should be an Active rectifier
using an op-amp and set for averaging output.
some formula that you use? Also, regarding the op-amp amplifier, what
do you actually do to it to get in to output the average, do you put a diode
or/and a capacitor at the output ?
Take care.......Gary
R
R. Steve Walz
Guest
Ewan Sinclair wrote:
Get a voltmeter and find out what voltages power the sections of the
device, and then you can use the sections separately.
-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public
Your best teacher is the hardware itself, since it actually once worked.I have been collecting busted old hardware so that I can harvest components
from it. However, being relatively new to all things electronic, I have come
up against a fair whack of problems as concerns determining the parameters
of the components I extract.
My current problem is how to light up a little PCB from an Apple Laserwriter
II (it has the status lights on it). The board has 6 conductors going onto
it (though one seems not to be connected to anything), which light up any of
4 pairs of tri-colour LEDs under some non-removable frosted plastic. Any
idea on how to find out which voltages to put up which conductors to acheive
what effects without cooking the LEDs? The thing has 4 resistors of varying
values, and one conductor of the 6 is attached to all 4 LED units directly.
I checked for every number on the board on the web, no luck. It's a funky
little thing and I'd like to be able to use it.
In fact, does anyone know of any decent guidelines for determining how
mystery components and circuits are driven? Old hardware is such a good
source for bits and bobs; it seems a shame to waste it all. Not to mention
that you can find some wonderful goodies in there. It'd be nice to learn how
to assimilate parts.
Ewan
------------
Get a voltmeter and find out what voltages power the sections of the
device, and then you can use the sections separately.
-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public
G
Glen Walpert
Guest
On Mon, 28 Jul 2003 14:09:36 -0700, Don Lancaster <don@tinaja.com>
wrote:
film resistance on the surface of your sphere. A reasonable first
approximation of the air boundary thermal resistance for the laminar
flow case typical for potted assemblies would be
h = 1.32(deltaT/d)^.25 watt/(m^2 C)
deltaT = surface temp - ambient air temp deg. C
d = sphere diameter in meters
(This is actually an approximation for convection of a cylinder in
free air from J.P. Holman, but it should be close enough for a sphere
considering the very approximate nature of these simplified equations
- there is not much variation in h with changes in shape with laminar
flow eg 1.32 changes to 1.42 for vertical cylinder.)
If you figure a spherical source with fixed heat dissipation and
covered with potting compound of uniform thickness and include the
thermal resistance of the potting compound and the air film, you can
calculate the potting compound thickness which will result in minimum
temperature of the source, and also the source size where potting
compound will no longer be able to reduce the source temp.
mass no energy and no temperature. But these bulk material
calculations give way to quantum mechanics long before zero radius!
wrote:
This neglects the thermal resistance of the surrounding air, mostlyZiguy wrote:
I was trying to do some analysis and for simplicity I used a sphere instead
of a box to calculate the thermal resistance and I came to a strange
conclusion.
The thermal resistance of a sphere is 1/(4*pi*k*r), where k is the thermal
conductivity and r is the radius of the sphere. A you can see, the thermal
resistance is inversely proportional to the radius. So it mean that if you
increase the sphere, the delta temperature between the center and the
surface of it will decrease . I would have sais the opposite, no?
film resistance on the surface of your sphere. A reasonable first
approximation of the air boundary thermal resistance for the laminar
flow case typical for potted assemblies would be
h = 1.32(deltaT/d)^.25 watt/(m^2 C)
deltaT = surface temp - ambient air temp deg. C
d = sphere diameter in meters
(This is actually an approximation for convection of a cylinder in
free air from J.P. Holman, but it should be close enough for a sphere
considering the very approximate nature of these simplified equations
- there is not much variation in h with changes in shape with laminar
flow eg 1.32 changes to 1.42 for vertical cylinder.)
If you figure a spherical source with fixed heat dissipation and
covered with potting compound of uniform thickness and include the
thermal resistance of the potting compound and the air film, you can
calculate the potting compound thickness which will result in minimum
temperature of the source, and also the source size where potting
compound will no longer be able to reduce the source temp.
Indeed, with zero radius it can neither conduct or radiate, it has no"Roy McCammon" <rbmccammon@ieee.org> a écrit dans le message de
news:3F233AEC.3070703@ieee.org...
Ziguy wrote:
I need to calculate the Inside to ambiant thermal resistance of a small
plastic box filled with potted resin... How do I calculate that, what're
the
properties needed?
As a first approximation, you can take the resin
filled box as all the same temperature and the
thermal resistance from the case to the air
will determine the box/resin temperature.
Achilles: I wish my wish would not be granted.
an undescribable event occurs
Achilles: What happened? Where's my Genie?
Tortoise: Our context got restored incorrectly.
Achilles: What does that cryptic comment mean?
Tortoise: The system crashed.
To email me send to :
rb <my last name> AT ieee DOT org
Thus a zero radius would have infinite thermal resistance and be a
perfect insulator.
mass no energy and no temperature. But these bulk material
calculations give way to quantum mechanics long before zero radius!
R
R.Legg
Guest
Glen Walpert <gwalpert@notaxs.com> wrote in message news:<rdrcivk5lvnsh7a1f1dusb61d3jh62j55m@4ax.com>...
C rise for every milliwatt dissipated from a cm^2 of surface area.
The problem is not establishing the surface temperature, but
determining the the heat source temperature.
What is needed is a crude practical approximation of average 'l/w' for
the path between a sphere's center and it's surface. This will be a
fixed number related to the radius. This could then be combined with
the thermal impedance of the potting compound to determine a rough
deltaT from the surface to the center of a sphere for a known power
transfer.
The same approximation for other simple shapes might also be useful.
It will be more accurate for any situation where the thermal impedance
of the potting compound is much higher than the thermal impedance of
the air - ie in most practical situations. The average surface
temperature of the radiating shape is driven by this difference to be
reasonably uniform, if the surface is plain.
RL
This still works out to the crude practical approximation of 1 degreeOn Mon, 28 Jul 2003 14:09:36 -0700, Don Lancaster <don@tinaja.com
wrote:
Ziguy wrote:
I was trying to do some analysis and for simplicity I used a sphere instead
of a box to calculate the thermal resistance and I came to a strange
This neglects the thermal resistance of the surrounding air, mostly
film resistance on the surface of your sphere. A reasonable first
approximation of the air boundary thermal resistance for the laminar
flow case typical for potted assemblies would be
h = 1.32(deltaT/d)^.25 watt/(m^2 C)
deltaT = surface temp - ambient air temp deg. C
d = sphere diameter in meters
C rise for every milliwatt dissipated from a cm^2 of surface area.
The problem is not establishing the surface temperature, but
determining the the heat source temperature.
What is needed is a crude practical approximation of average 'l/w' for
the path between a sphere's center and it's surface. This will be a
fixed number related to the radius. This could then be combined with
the thermal impedance of the potting compound to determine a rough
deltaT from the surface to the center of a sphere for a known power
transfer.
The same approximation for other simple shapes might also be useful.
It will be more accurate for any situation where the thermal impedance
of the potting compound is much higher than the thermal impedance of
the air - ie in most practical situations. The average surface
temperature of the radiating shape is driven by this difference to be
reasonably uniform, if the surface is plain.
RL
J
John Larkin
Guest
On 29 Jul 2003 16:32:52 -0700, legg@magma.ca (R.Legg) wrote:
sections, and they get very small close-in to the inner sphere. For a
small inner sphere, most of the temperature gradient is very close to
the inner sphere, so the "average" cross-sectional area of the thermal
path is not meaningful.
I posted the exact equation, um, somewhere nearby. For smallish inner
radius r, thermal resistance goes up as 1/r. That means the OP should
try to spread the heat source out as much as possible, maybe with PCB
foil and vias, if cooling is critical. Or maybe mount the TO-220
upside down?
John
The conductive path can be divided up into a bunch of taperedIf the single temperature source occupied a concentric sphere with
1/100th the radius of the external radiating surface, then the path
length is equal to the radius and the average cross-sectional area of
the path is still about 33% of the external surface area.
sections, and they get very small close-in to the inner sphere. For a
small inner sphere, most of the temperature gradient is very close to
the inner sphere, so the "average" cross-sectional area of the thermal
path is not meaningful.
I posted the exact equation, um, somewhere nearby. For smallish inner
radius r, thermal resistance goes up as 1/r. That means the OP should
try to spread the heat source out as much as possible, maybe with PCB
foil and vias, if cooling is critical. Or maybe mount the TO-220
upside down?
John
D
DarkMatter
Guest
On Tue, 29 Jul 2003 16:53:25 -0700, John Larkin
<jjlarkin@highSNIPlandTHIStechPLEASEnology.com> Gave us:
shouldn't as device specs have limits to their allowable
characteristics in the industry as well.
We have products where the main transistor are only potted up to the
hole, which means that their dies are coupled to the potting.
We have some, that we only dipped a couple of few times, and the
potting still conducts the heat away fast enough.
A 2n4923 can only pass one amp. The thing is whether you are
passing the amp, or dissipating some losses due to poor circuit
efficiency.
<jjlarkin@highSNIPlandTHIStechPLEASEnology.com> Gave us:
If he operates it inside of its spec, it will never get that hot, orOn 29 Jul 2003 16:32:52 -0700, legg@magma.ca (R.Legg) wrote:
If the single temperature source occupied a concentric sphere with
1/100th the radius of the external radiating surface, then the path
length is equal to the radius and the average cross-sectional area of
the path is still about 33% of the external surface area.
The conductive path can be divided up into a bunch of tapered
sections, and they get very small close-in to the inner sphere. For a
small inner sphere, most of the temperature gradient is very close to
the inner sphere, so the "average" cross-sectional area of the thermal
path is not meaningful.
I posted the exact equation, um, somewhere nearby. For smallish inner
radius r, thermal resistance goes up as 1/r. That means the OP should
try to spread the heat source out as much as possible, maybe with PCB
foil and vias, if cooling is critical. Or maybe mount the TO-220
upside down?
shouldn't as device specs have limits to their allowable
characteristics in the industry as well.
We have products where the main transistor are only potted up to the
hole, which means that their dies are coupled to the potting.
We have some, that we only dipped a couple of few times, and the
potting still conducts the heat away fast enough.
A 2n4923 can only pass one amp. The thing is whether you are
passing the amp, or dissipating some losses due to poor circuit
efficiency.
A
A E
Guest
Shadow wrote:
igniters are cheap.
Uh, why don't you buy a model rocket launch system? All done for you, andHello all, I have a simple question. I'm into fireworks pretty big, and
because of this(and the fact that the 4th July/lighting fireworks has
ended/is slowly dying out for this year), I have come to the conclusion that
I am getting tired of lighting fuses, and running fast and far from the
bigger fireworks(consumer artillery shells, larger shell cakes, larger
fountains[2-3 minute duration] etc.). I know for a fact that you can take a
lawn mower battery that has decent amperage and ignite steel wool with it.
You can do the same thing with a car battery. And, if you're into the
theroy of explosives(please, no stories about building home-made stuff), you
know that you can 'detonate' certain things with electricity. Also, model
rocketry uses car batteries to ignite them.
My first question is, if you hook 8 AA batteries together in series(1.5v
X 8 = 12v), you would produce a 12v charge. I know this works as I used
some little slot machine game(nearest thing within reach) to apply this
voltage too. This Slot Machine handheld game calls for 1.5v from a AAA
battery. The music, and sound effects were higher in pitch and faster with
the higher voltage being applied to them. This is common sense/a good
thing(I think). Would the 12v alone be enough to ignite steel wool, or does
the amperage in a lawn mower battery/car battery play a heavy role in being
able to heat up steel wool until it's red hot/to the point of slightly
combusting?
If this is the case(which I think it is), would a lawn mower battery
that advertises 380 amps be good for doing this? If so, this would be good.
I could put a Toggle style Microswitch on the hot wire somewhere, and I have
ignition, at the point of a switch, from a safe distance(25-50 feet).
Finally! I don't have to run from artiller shells anymore.
If all of this is fine and good, I have a little bit more complex of a
question. Would I be able to use a lawn mower battery, or a car battery as
a "central power house" and build some type of a swtiching system for it?
What I'm thinking about doing is this: Setting up so many fireworks, ready
to go. Steel wool, heavy wire to take the charge and apply it to the steel
wool, and the whole works. Building a project box with 2 rows of switches.
2 rows, 2 columns. Say, a 2x6 grid of switches. All of colum one, ignites
the first firework. Row 1, column 1, puts control towards the first
firework. Row 2, column 1, actually ignites the firework. Row 1, coumn 2,
puts control towards the 2nd firework. Row 2, column 2, actually ignites
the firework....and so on, all using this one single high-amperage battery
as the "powerhouse" for actually applying a charge.
Sound good? Bad idea? Any tips on doing it? I know very little about
electronics(some, but not anything nasty), so, please lend a helping hand.
----------
The world is waiting, I must leave you now.
igniters are cheap.
S
Sir Charles W. Shults III
Guest
Any path can be a shunt- in this case, you use a resistor. The dictionary
defines it as "a conductor having low resistance in parallel with another device
to divert a fraction of the current" but we can use a high resistance and
measure the voltage drop across it.
Given the resistance and voltage relationships, we can deduce the current
through the resistor by the voltage drop across it.
Cheers!
Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
defines it as "a conductor having low resistance in parallel with another device
to divert a fraction of the current" but we can use a high resistance and
measure the voltage drop across it.
Given the resistance and voltage relationships, we can deduce the current
through the resistor by the voltage drop across it.
Cheers!
Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
N
Nir Goren
Guest
I feel kind of dumb to ask this, but what is a "shunt" ??
"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message
news:C2vVa.176582$ic1.4014172@twister.tampabay.rr.com...
"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message
news:C2vVa.176582$ic1.4014172@twister.tampabay.rr.com...
Well, if you have a precision resistor you can use as a shunt, your
DAC can
provide a voltage that will source the shunt resistor. The resistor will
limit
your current, and if it is one megohm, you end up with a microamp per
volt.
Now, for feedback, you can measure the voltage drop across the shunt
and use
a precision op amp to compare the output voltage and the shunt voltage-
this can
be your error signal. A little creative buffering and you can feed that
voltage
back to the shunt resistor to correct for the error.
I'm sure that somebody in the group might have a better method, but
that
comes to mind right away for me.
Cheers!
Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
R
R.Legg
Guest
John Larkin <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in message news:<jd1eivsb3cki17lsnpg5ift04t3e7umr89@4ax.com>...
dimension. The fact that the area and the impedance varies along the
path is the irrelevent complication that this calculation is designed
to avoid.
related to change of the surface area of the concentric sphere at the
radius being examined. Surface are is 4 . pi . r^2.
If you mean that at similar r values, the squaring effect is
minimized, I can agree with you, but then most other effects become
irrelevent too, including thermal impedance of the intervening
material. Potting isn't thin-all insulation.
of action is required to reduce the delta through the potting
material. This is the effect of making the radiator r being 1/2 the
external surface r.
The two examples at 1/10th and 1/100th r were intended to show that
point-source radiation was a mathematical abstraction, and that real
effects were not going to outweigh published thermal impedance from
junction to case at the source when this scale was present.
The other observation that I hope was noted, and may have been glossed
over as being too obvious, was that the other limit on achievable
temperatures was the mechanical limit of the external surface area.
Averages are your friend. Extra decimal places are hogwash. The sexier
terms for calculating this effective average do exist; leave them
those who want to impress their girlfriends and co-workers. We are
attempting a practical understanding here.
RL
The average cross-sectional area is the meaningful and effectiveOn 29 Jul 2003 16:32:52 -0700, legg@magma.ca (R.Legg) wrote:
If the single temperature source occupied a concentric sphere with
1/100th the radius of the external radiating surface, then the path
length is equal to the radius and the average cross-sectional area of
the path is still about 33% of the external surface area.
The conductive path can be divided up into a bunch of tapered
sections, and they get very small close-in to the inner sphere. For a
small inner sphere, most of the temperature gradient is very close to
the inner sphere, so the "average" cross-sectional area of the thermal
path is not meaningful.
dimension. The fact that the area and the impedance varies along the
path is the irrelevent complication that this calculation is designed
to avoid.
resistance increases proportionally to 1 / (r^2) - the increase isI posted the exact equation, um, somewhere nearby. For smallish inner
radius r, thermal resistance goes up as 1/r.
related to change of the surface area of the concentric sphere at the
radius being examined. Surface are is 4 . pi . r^2.
If you mean that at similar r values, the squaring effect is
minimized, I can agree with you, but then most other effects become
irrelevent too, including thermal impedance of the intervening
material. Potting isn't thin-all insulation.
If he finds out that the part IS overtemped, then of course some kindThat means the OP should
try to spread the heat source out as much as possible, maybe with PCB
foil and vias, if cooling is critical. Or maybe mount the TO-220
upside down?
of action is required to reduce the delta through the potting
material. This is the effect of making the radiator r being 1/2 the
external surface r.
The two examples at 1/10th and 1/100th r were intended to show that
point-source radiation was a mathematical abstraction, and that real
effects were not going to outweigh published thermal impedance from
junction to case at the source when this scale was present.
The other observation that I hope was noted, and may have been glossed
over as being too obvious, was that the other limit on achievable
temperatures was the mechanical limit of the external surface area.
Averages are your friend. Extra decimal places are hogwash. The sexier
terms for calculating this effective average do exist; leave them
those who want to impress their girlfriends and co-workers. We are
attempting a practical understanding here.
RL
L
Laurence Dishman
Guest
"Nir Goren" <nirg@bgumail.bgu.ac.il> wrote in message news:<bg5tko$89m$1@news.iucc.ac.il>...
Use a PNP transistor with the emitter connected to a precision
resistor which is connected to V+. Connect a Digital to Voltage
Converter between V+ and the base of the transistor.
The Voltage across the resistor will be the same as the DAC voltage.
The current will be V/resistance. This current will be available at
the collector of the transistor.
Hi,
I need to deign a controlled current source for several tens of uA say about
150uA witch have to be very accurate and vary stable. I'd like to control
this source by some sort of DAC preferably use a 12bit V out DAC witch I
already have on board.
So far searching Analog, Liner ,Maxim, etc.. have gotten me no where.
Pleas help.
Nir goren
Use a PNP transistor with the emitter connected to a precision
resistor which is connected to V+. Connect a Digital to Voltage
Converter between V+ and the base of the transistor.
The Voltage across the resistor will be the same as the DAC voltage.
The current will be V/resistance. This current will be available at
the collector of the transistor.
BGU uni
VLSI Center
M
Mark Fergerson
Guest
Randy wrote:
electrons are free to move. In the dielectric, they aren't,
but their orbitals can be distorted in response to external
fields. When the plates are charged by the voltage source
(an external field is applied to the assembly), the free
electrons move but the dielectrics' electrons orbitals
merely distort.
It may help to think of the free electrons in the plates
as having orbitals whose distortability extends to infinity,
so to speak. The electrons in the dielectric are then a bit
handicapped by comparison, that's all.
Mark L. Fergerson
What's confusing? In the (presumably metal) plates,K factor for this purpose is unity.
"When connected to a voltage source (a battery in this case), the voltage
forces electrons onto one plate, making it negative, and pulls them off the
other, making it positive. Electrons cannot flow through the dielectric."
If electrons are in a bound orbital state between the plates, unable to be
forced on or off of either plate, and energy is transferred from the
electrostatic field to the electrons of each atom between the plates by
distorting the orbits, then this statement is a bit confusing.
electrons are free to move. In the dielectric, they aren't,
but their orbitals can be distorted in response to external
fields. When the plates are charged by the voltage source
(an external field is applied to the assembly), the free
electrons move but the dielectrics' electrons orbitals
merely distort.
It may help to think of the free electrons in the plates
as having orbitals whose distortability extends to infinity,
so to speak. The electrons in the dielectric are then a bit
handicapped by comparison, that's all.
Mark L. Fergerson
Z
Ziguy
Guest
By the way, here's a schematic to help you understand...
http://www3.sympatico.ca/latourr/Protect.jpg
"Ziguy" <robertlatour54@hotmail.NOSPAM.com> a écrit dans le message de
news:b9VVa.30$qN3.9604@news20.bellglobal.com...
http://www3.sympatico.ca/latourr/Protect.jpg
"Ziguy" <robertlatour54@hotmail.NOSPAM.com> a écrit dans le message de
news:b9VVa.30$qN3.9604@news20.bellglobal.com...
I design a automotive application that has 3 wires (supply, ground and a
output). Internaly, this output is connected to the ouput of a high side
power mosfet switch. In order to protect my circuit from wrong connection,
I
put a diode in serie with the output but now I have big problems with
power
dissipation. The output can source up to 5A.
Instead, what do you think if I putting a diode between the supply and the
output??? That way, if the user connect the supply wire to the ground and
the output wire to the battery+ (my last unprotected fatal scenario), he
will only blow his fuse!
Good idea?
J
Joshua K Drumeller
Guest
Ah Shadow,
You sound just like me. J
The thing about steel wool is that if you were to hook a wire to it and hook
it to a battery by way of a switch the steel wool will not always ignite.
The best way to get it to ignite is to stroke a 9 volt battery across it. It
will cause sparks which will then ignite the steel wool. I wouldn't use a
car battery or a lawnmower battery. If you must use something bigger than a
9 volt which you don't really need to just use 2 of those 6 volt lantern
batteries. They will last a long time.
If you want to hook up an electronic detonator try this little trick. Take
some of those thin small Christmas lights and break the glass around it. Be
careful not to destroy what is on the inside of the glass. Now the end which
normally glows can go on your fuse or in the gunpowder directly. You can
hook wires to the 2 leads where the electricity comes from. You can use a 9
volt battery to make it glow. Once it glows it will glow hot enough to
ignite the gunpowder or the fuse or steel wool or whatever. It is a lot
cheaper than buying model rocket engine igniters and it is easier to ignite
fireworks in stages. Then you can hook several of these up with some
switches and a battery to shoot of what ever you want.
Josh
"Shadow" <vot@charter.net> wrote in message
news:viecumg2bvu943@corp.supernews.com...
You sound just like me. J
The thing about steel wool is that if you were to hook a wire to it and hook
it to a battery by way of a switch the steel wool will not always ignite.
The best way to get it to ignite is to stroke a 9 volt battery across it. It
will cause sparks which will then ignite the steel wool. I wouldn't use a
car battery or a lawnmower battery. If you must use something bigger than a
9 volt which you don't really need to just use 2 of those 6 volt lantern
batteries. They will last a long time.
If you want to hook up an electronic detonator try this little trick. Take
some of those thin small Christmas lights and break the glass around it. Be
careful not to destroy what is on the inside of the glass. Now the end which
normally glows can go on your fuse or in the gunpowder directly. You can
hook wires to the 2 leads where the electricity comes from. You can use a 9
volt battery to make it glow. Once it glows it will glow hot enough to
ignite the gunpowder or the fuse or steel wool or whatever. It is a lot
cheaper than buying model rocket engine igniters and it is easier to ignite
fireworks in stages. Then you can hook several of these up with some
switches and a battery to shoot of what ever you want.
Josh
"Shadow" <vot@charter.net> wrote in message
news:viecumg2bvu943@corp.supernews.com...
Hello all, I have a simple question. I'm into fireworks pretty big,
and
because of this(and the fact that the 4th July/lighting fireworks has
ended/is slowly dying out for this year), I have come to the conclusion
that
I am getting tired of lighting fuses, and running fast and far from the
bigger fireworks(consumer artillery shells, larger shell cakes, larger
fountains[2-3 minute duration] etc.). I know for a fact that you can take
a
lawn mower battery that has decent amperage and ignite steel wool with it.
You can do the same thing with a car battery. And, if you're into the
theroy of explosives(please, no stories about building home-made stuff),
you
know that you can 'detonate' certain things with electricity. Also, model
rocketry uses car batteries to ignite them.
My first question is, if you hook 8 AA batteries together in
series(1.5v
X 8 = 12v), you would produce a 12v charge. I know this works as I used
some little slot machine game(nearest thing within reach) to apply this
voltage too. This Slot Machine handheld game calls for 1.5v from a AAA
battery. The music, and sound effects were higher in pitch and faster
with
the higher voltage being applied to them. This is common sense/a good
thing(I think). Would the 12v alone be enough to ignite steel wool, or
does
the amperage in a lawn mower battery/car battery play a heavy role in
being
able to heat up steel wool until it's red hot/to the point of slightly
combusting?
If this is the case(which I think it is), would a lawn mower battery
that advertises 380 amps be good for doing this? If so, this would be
good.
I could put a Toggle style Microswitch on the hot wire somewhere, and I
have
ignition, at the point of a switch, from a safe distance(25-50 feet).
Finally! I don't have to run from artiller shells anymore.
If all of this is fine and good, I have a little bit more complex of a
question. Would I be able to use a lawn mower battery, or a car battery
as
a "central power house" and build some type of a swtiching system for it?
What I'm thinking about doing is this: Setting up so many fireworks,
ready
to go. Steel wool, heavy wire to take the charge and apply it to the
steel
wool, and the whole works. Building a project box with 2 rows of
switches.
2 rows, 2 columns. Say, a 2x6 grid of switches. All of colum one,
ignites
the first firework. Row 1, column 1, puts control towards the first
firework. Row 2, column 1, actually ignites the firework. Row 1, coumn
2,
puts control towards the 2nd firework. Row 2, column 2, actually ignites
the firework....and so on, all using this one single high-amperage battery
as the "powerhouse" for actually applying a charge.
Sound good? Bad idea? Any tips on doing it? I know very little about
electronics(some, but not anything nasty), so, please lend a helping hand.
----------
The world is waiting, I must leave you now.
W
w_tom
Guest
Are you familiar with common emitter resistors so that too
much current through transistor collector causes a decrease in
base current? Just a simple solution. Other more complex
solutions would cause a cutoff in base current when output
collector current gets too high. Also Schottky diodes
dissipate less power.
Ziguy wrote:
much current through transistor collector causes a decrease in
base current? Just a simple solution. Other more complex
solutions would cause a cutoff in base current when output
collector current gets too high. Also Schottky diodes
dissipate less power.
Ziguy wrote:
I design a automotive application that has 3 wires (supply, ground and a
output). Internaly, this output is connected to the ouput of a high side
power mosfet switch. In order to protect my circuit from wrong connection, I
put a diode in serie with the output but now I have big problems with power
dissipation. The output can source up to 5A.
Instead, what do you think if I putting a diode between the supply and the
output??? That way, if the user connect the supply wire to the ground and
the output wire to the battery+ (my last unprotected fatal scenario), he
will only blow his fuse!
Good idea?
S
Shadow
Guest
Thank you for your advice Josh. I do have 2 packs of Estes model rocket
engines, and 4 model rocket bodies that I've had lying around for years.
However, just a few seconds ago I did the following:
I took a pair of jumper cables, and I hooked them up to a car battery, while
the car was shut off, but while the battery cables for the vehicle itself
were still hooked up, leading into the rest of the engine compartment
somewhere. (Aiming for less of a hassle, and easy here)
I took a good number of steel wool threads, about 6 inches in length, with
the entire bunch having about a 1/2" diameter, and I attached approximately
a 4-5 inch long length of 16 guage speaker wire onto each end of the steel
wool bundle.
I then hooked the 'live' jumper cables up to each speaker wire cable, and
WOOF, instantly the steel wool combusted. After waiting around a few
minutes, I tested again, and instead of combusting, the steel wool instead
became red hot which is good enough for ignition, but I don't know if it
would be an instant detonation versus the steel wool combusting straight
into raw gun powder/whatever. The point is, is I'm happy with this, and
will try it out. I'll buy some toggle switches, and a project box, and bang
my head against the wall for a few hours.
Your ideas sound like fun though Josh, and I'll probably refer to your reply
a couple of times trying some things out that you mention.
Thanks!
"Joshua K Drumeller" <lkfightr@swbell.net> wrote in message
news:ElVVa.4684$gZ7.197@newssvr23.news.prodigy.com...
engines, and 4 model rocket bodies that I've had lying around for years.
However, just a few seconds ago I did the following:
I took a pair of jumper cables, and I hooked them up to a car battery, while
the car was shut off, but while the battery cables for the vehicle itself
were still hooked up, leading into the rest of the engine compartment
somewhere. (Aiming for less of a hassle, and easy here)
I took a good number of steel wool threads, about 6 inches in length, with
the entire bunch having about a 1/2" diameter, and I attached approximately
a 4-5 inch long length of 16 guage speaker wire onto each end of the steel
wool bundle.
I then hooked the 'live' jumper cables up to each speaker wire cable, and
WOOF, instantly the steel wool combusted. After waiting around a few
minutes, I tested again, and instead of combusting, the steel wool instead
became red hot which is good enough for ignition, but I don't know if it
would be an instant detonation versus the steel wool combusting straight
into raw gun powder/whatever. The point is, is I'm happy with this, and
will try it out. I'll buy some toggle switches, and a project box, and bang
my head against the wall for a few hours.
Your ideas sound like fun though Josh, and I'll probably refer to your reply
a couple of times trying some things out that you mention.
Thanks!
"Joshua K Drumeller" <lkfightr@swbell.net> wrote in message
news:ElVVa.4684$gZ7.197@newssvr23.news.prodigy.com...
Ah Shadow,
You sound just like me. J
The thing about steel wool is that if you were to hook a wire to it and
hook
it to a battery by way of a switch the steel wool will not always ignite.
The best way to get it to ignite is to stroke a 9 volt battery across it.
It
will cause sparks which will then ignite the steel wool. I wouldn't use a
car battery or a lawnmower battery. If you must use something bigger than
a
9 volt which you don't really need to just use 2 of those 6 volt lantern
batteries. They will last a long time.
If you want to hook up an electronic detonator try this little trick. Take
some of those thin small Christmas lights and break the glass around it.
Be
careful not to destroy what is on the inside of the glass. Now the end
which
normally glows can go on your fuse or in the gunpowder directly. You can
hook wires to the 2 leads where the electricity comes from. You can use a
9
volt battery to make it glow. Once it glows it will glow hot enough to
ignite the gunpowder or the fuse or steel wool or whatever. It is a lot
cheaper than buying model rocket engine igniters and it is easier to
ignite
fireworks in stages. Then you can hook several of these up with some
switches and a battery to shoot of what ever you want.
Josh
"Shadow" <vot@charter.net> wrote in message
news:viecumg2bvu943@corp.supernews.com...
Hello all, I have a simple question. I'm into fireworks pretty big,
and
because of this(and the fact that the 4th July/lighting fireworks has
ended/is slowly dying out for this year), I have come to the conclusion
that
I am getting tired of lighting fuses, and running fast and far from the
bigger fireworks(consumer artillery shells, larger shell cakes, larger
fountains[2-3 minute duration] etc.). I know for a fact that you can
take
a
lawn mower battery that has decent amperage and ignite steel wool with
it.
You can do the same thing with a car battery. And, if you're into the
theroy of explosives(please, no stories about building home-made stuff),
you
know that you can 'detonate' certain things with electricity. Also,
model
rocketry uses car batteries to ignite them.
My first question is, if you hook 8 AA batteries together in
series(1.5v
X 8 = 12v), you would produce a 12v charge. I know this works as I used
some little slot machine game(nearest thing within reach) to apply this
voltage too. This Slot Machine handheld game calls for 1.5v from a AAA
battery. The music, and sound effects were higher in pitch and faster
with
the higher voltage being applied to them. This is common sense/a good
thing(I think). Would the 12v alone be enough to ignite steel wool, or
does
the amperage in a lawn mower battery/car battery play a heavy role in
being
able to heat up steel wool until it's red hot/to the point of slightly
combusting?
If this is the case(which I think it is), would a lawn mower battery
that advertises 380 amps be good for doing this? If so, this would be
good.
I could put a Toggle style Microswitch on the hot wire somewhere, and I
have
ignition, at the point of a switch, from a safe distance(25-50 feet).
Finally! I don't have to run from artiller shells anymore.
If all of this is fine and good, I have a little bit more complex of
a
question. Would I be able to use a lawn mower battery, or a car battery
as
a "central power house" and build some type of a swtiching system for
it?
What I'm thinking about doing is this: Setting up so many fireworks,
ready
to go. Steel wool, heavy wire to take the charge and apply it to the
steel
wool, and the whole works. Building a project box with 2 rows of
switches.
2 rows, 2 columns. Say, a 2x6 grid of switches. All of colum one,
ignites
the first firework. Row 1, column 1, puts control towards the first
firework. Row 2, column 1, actually ignites the firework. Row 1, coumn
2,
puts control towards the 2nd firework. Row 2, column 2, actually
ignites
the firework....and so on, all using this one single high-amperage
battery
as the "powerhouse" for actually applying a charge.
Sound good? Bad idea? Any tips on doing it? I know very little about
electronics(some, but not anything nasty), so, please lend a helping
hand.
----------
The world is waiting, I must leave you now.
K
Kevin Kilzer
Guest
On Wed, 30 Jul 2003 18:35:46 +0800, "Raymond" <raywail@hotmail.com>
wrote:
and so limits the radio signals that come and go. If the lift happens
to be close to the cell-site antenna, then enough signal gets through
to be useful.
Other things can block the signal, too, like metal frames in big
buildings, and sometimes just any building will block the signal.
The heigth and orientation of the antenna has an affect, too.
Kevin
wrote:
Its all a matter of signal strength. The lift cage is mostly metal,Sorry for my silly question. I want to ask why my mobile cannot receive
signal or call another in some lift? and why it can in some lift?
and so limits the radio signals that come and go. If the lift happens
to be close to the cell-site antenna, then enough signal gets through
to be useful.
Other things can block the signal, too, like metal frames in big
buildings, and sometimes just any building will block the signal.
The heigth and orientation of the antenna has an affect, too.
Kevin
J
Jonathan Kirwan
Guest
On Thu, 31 Jul 2003 07:54:46 +0200, "Nir Goren"
<nirg@bgumail.bgu.ac.il> wrote:
here. What about the other questions I asked? And what about
when you turn it off and turn in on again a different day? And
if you build a second one and try it?
And I gather you mean a maximum of 150uA with 2uA as the
resolution? Just one part in 75??
Jon
<nirg@bgumail.bgu.ac.il> wrote:
Stable does not mean accurate. I gather you mean the precision,"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in message
news:116giv0vocdn3m1ce4i8fh6jjnveq7ansn@4ax.com...
On Tue, 29 Jul 2003 16:42:20 +0200, "Nir Goren"
nirg@bgumail.bgu.ac.il> wrote:
I need to deign a controlled current source for several tens of uA say
about
150uA witch have to be very accurate and vary stable. I'd like to control
this source by some sort of DAC preferably use a 12bit V out DAC witch I
already have on board.
So far searching Analog, Liner ,Maxim, etc.. have gotten me no where.
So you want an _accurate_ current source, not just a repeatable
one? How accurate?? And what kind of ambient temperature
variations must you tolerate in remaining this accurate? And
how long must it hold this accuracy?
And do you really need 1:4000 or .025% precision??? That kind
of precision isn't at all impossible, but it takes some good
effort to achieve, I think.
I neet it to be stable at arownd +-2uA. Air temprature contotions are normal
room (25C) with no more then +-2C varations. I wish not to control the
circet temprature.
here. What about the other questions I asked? And what about
when you turn it off and turn in on again a different day? And
if you build a second one and try it?
And I gather you mean a maximum of 150uA with 2uA as the
resolution? Just one part in 75??
Jon
N
Nir Goren
Guest
I neet it to be stable at arownd +-2uA. Air temprature contotions are normal
room (25C) with no more then +-2C varations. I wish not to control the
circet temprature.
"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in message
news:116giv0vocdn3m1ce4i8fh6jjnveq7ansn@4ax.com...
room (25C) with no more then +-2C varations. I wish not to control the
circet temprature.
"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in message
news:116giv0vocdn3m1ce4i8fh6jjnveq7ansn@4ax.com...
On Tue, 29 Jul 2003 16:42:20 +0200, "Nir Goren"
nirg@bgumail.bgu.ac.il> wrote:
I need to deign a controlled current source for several tens of uA say
about
150uA witch have to be very accurate and vary stable. I'd like to control
this source by some sort of DAC preferably use a 12bit V out DAC witch I
already have on board.
So far searching Analog, Liner ,Maxim, etc.. have gotten me no where.
So you want an _accurate_ current source, not just a repeatable
one? How accurate?? And what kind of ambient temperature
variations must you tolerate in remaining this accurate? And
how long must it hold this accuracy?
And do you really need 1:4000 or .025% precision??? That kind
of precision isn't at all impossible, but it takes some good
effort to achieve, I think.
Jon