Chip with simple program for Toy

[John Damm Sřrensen]

Data888 wrote:

Another IC-related question. I'm sort of playing with the ICs and trying
to build an audio switch at the same time.
I have the 4051 analog multiplexer semi-working. I have +5v on VDD, VSS
grounded, INH grounded. When the control inputs A, B & C are grounded,
there is a connection between OUT/IN and output 0. However, my
multimeter shows the resistance as over 300ohms. I think that it should
be lower, more like < 100ohms.
Also, I'm not sure what to do with VEE. From what I can understand, I
should make it -5v. If that's true, can I get -5v from my +5v supply
(from a 7805 regulator), or do I need to buy a 7905 regulator and create
the supply separately?
Thanks,

Nick

Nick,

From the datasheet http://www.fairchildsemi.com/ds/CD/CD4051BC.pdf the
on resistance is OK for a supply voltage of just +5V.
If you want lower resistance you must use a higher voltage.
Vee should be negative if you intend to switch AC signals otherwise it
shoul bed tied to ground (Vss).
Maxim (www.maxim-ic.com) has IC's that can generate -5 V from a +5V source.

John

 

[Data888]

John Damm Sřrensen wrote:

Data888 wrote:

Another IC-related question. I'm sort of playing with the ICs and
trying to build an audio switch at the same time.
I have the 4051 analog multiplexer semi-working. I have +5v on VDD,
VSS grounded, INH grounded. When the control inputs A, B & C are
grounded, there is a connection between OUT/IN and output 0. However,
my multimeter shows the resistance as over 300ohms. I think that it
should be lower, more like < 100ohms.
Also, I'm not sure what to do with VEE. From what I can understand, I
should make it -5v. If that's true, can I get -5v from my +5v supply
(from a 7805 regulator), or do I need to buy a 7905 regulator and
create the supply separately?
Thanks,

Nick

Nick,
From the datasheet http://www.fairchildsemi.com/ds/CD/CD4051BC.pdf the
on resistance is OK for a supply voltage of just +5V.
If you want lower resistance you must use a higher voltage.
Vee should be negative if you intend to switch AC signals otherwise it
shoul bed tied to ground (Vss).
Maxim (www.maxim-ic.com) has IC's that can generate -5 V from a +5V source.

John

OK, so looks like I'll have to go get a 7905, as line-level audio
signals are AC. Thanks for your help.

Nick

 

[A E]

"Dana Raymond, a minor God" wrote:

Why a joystick?
If you wish to have the computer measure and possibly record the wheel
speed, and the wheel already has a pule sensor, then get a CTC card from
computerboards inc or metrabyte or use software to count pulses from the
parralel or serial port to do the job.

If a joystick POT is a requirement then some custom electronics could be
designed. Perhaps an opamp buffer/integrator that converts the pulse
frequency into a voltage that would replace the POT wiper voltage.

Hope this helps.
Dana Raymond

AFAIK, PC joysticks don't sense a voltage, they charge a cap through the
resistance of a pot, and count the time to discharge. I'd use a digital pot
instead of driving a voltage into the joystick input.

 

[Craig]

Adam Brown wrote:

Hi,

My electrical knowledge is minimal. I'd like to convert the speed of a wind
trainer into the forward input of a computer joystick. I can use a cheap
cycle computer which generates small pulses of current each time the wheel
rotates. Is there a simple way to use these pulses to control the
resistance in the joystick that controls forwards/backwards.

Some quick research suggests another alternative might be to use a dynamo
which might in turn control a JFET which could replace the joystick
potentiameter.

The cycle computer options is the most elegant. Is there a circuit that can
be built to smooth the pulses to provide a constant voltage which can be
applied to the JFET?

Is there an altogether superior solution?

Any help appreciated,

Adam

if it doesn't have to be a joystick you could use an optical encoder -
like on a mouse. in fact with some gaffa tape, dremmel and patience you
could use an old mouse, one encoder on a roller on a spinning bit for
forward and one on your handle bars for left and right with some
tinkering you may be able to use the blades of your wind trainer but it
would need to be covered to keep it dark which would limit air flow.

craig

 

[Baphomet]

"Dana Raymond, a minor God" <raymonds4@austin.rr.com> wrote in message
news:81qWa.124109$TJ.7631334@twister.austin.rr.com...

" If a joystick POT is a requirement then some custom electronics could be
designed. Perhaps an opamp buffer/integrator that converts the pulse
frequency into a voltage that would replace the POT wiper voltage.

Hope this helps.
Dana Raymond


Dana -

In one of the first two way television experiments, we had to control the
paddle in "video pong" using telco touch tones. Replacing the pot with a
control voltage resulted in severe linearity problems (control voltage vs.
paddle movement). While we were able to "shape" the control voltage to
minimize the non-linearity, it was an unelegant fix...but it did work.

 

[Chris1]

In article <vigle5lcave595@corp.supernews.com>, "Shadow" <vot@charter.net> wrote:

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.

I once made an ignitor by wrapping a few inches of very fine copper wire
around a paper match head. I just used a single strand from some stranded
18ga wire. I could fire it with a single D cell, but that was with very
short leads. A long run might require 6v or more.

Chris

 

[John Larkin]

On 31 Jul 2003 16:35:15 -0700, legg@magma.ca (R.Legg) wrote:

Consider a pipe a mile long, 100" diameter at one end, tapering off to
1" at the other. Would water flow as well in this pipe as in one that
was uniformly 57 inches (which would have 33% of the inlet area)?



I posted the exact equation, um, somewhere nearby. For smallish inner
radius r, thermal resistance goes up as 1/r.

resistance increases proportionally to 1 / (r^2) - the increase is
related to change of the surface area of the concentric sphere at the
radius being examined. Surface are is 4 . pi . r^2.


The equation was

R = rho(1/r2 - 1/r1)/4*pi

You were correct to question the 33% figure. I'm sort of dissapointed
that you didn't take the time to do a bit of figuring and suggest a
better one.

Because "average cross-sectional area" is useless here; it tells you
nothing about the actual thermal resistance. Especially when the
actual equation is right there.

I may be wrong. Perhaps you have a different perspective to offer,
with some ball-park numbers. Please don't use plumbing analogies,
these only go so far before you have to do things like relate delta T
to water velocity - if you have to, use current flow in conductors.

My point was that averaging areas makes no sense, for any kind of
flow. Why ballpark when you can have the real thing?

John

 

[Dana Raymond, a minor God]

Lets go back to basics here. What/why exactly are you trying to accomplish
Adam?
Start with that and then explain the selected sensor and the chosen computer
input method. You are limiting us in helping find a solution by providing
such little information.

Dana Raymond

"Dana Raymond, a minor God" <raymonds4@austin.rr.com> wrote in message
news:81qWa.124109$TJ.7631334@twister.austin.rr.com...

Why a joystick?
If you wish to have the computer measure and possibly record the wheel
speed, and the wheel already has a pule sensor, then get a CTC card from
computerboards inc or metrabyte or use software to count pulses from the
parralel or serial port to do the job.

If a joystick POT is a requirement then some custom electronics could be
designed. Perhaps an opamp buffer/integrator that converts the pulse
frequency into a voltage that would replace the POT wiper voltage.

Hope this helps.
Dana Raymond

"Adam Brown" <adam@freestream.com.au> wrote in message
news:3f29fd55$0$95049$c30e37c6@lon-reader.news.telstra.net...
Hi,

My electrical knowledge is minimal. I'd like to convert the speed of a
wind
trainer into the forward input of a computer joystick. I can use a cheap
cycle computer which generates small pulses of current each time the
wheel
rotates. Is there a simple way to use these pulses to control the
resistance in the joystick that controls forwards/backwards.

Some quick research suggests another alternative might be to use a
dynamo
which might in turn control a JFET which could replace the joystick
potentiameter.

The cycle computer options is the most elegant. Is there a circuit that
can
be built to smooth the pulses to provide a constant voltage which can be
applied to the JFET?

Is there an altogether superior solution?

Any help appreciated,

Adam

 

[David Harmon]

On Fri, 1 Aug 2003 10:45:50 +0200 in sci.electronics.basics,
"Gnekker" <gnekker/removefilter/@yahoo.com> wrote:

Please explain to me why this is not a really bad idea... My
understanding is that holding CMOS inputs at V/2 can cause large
power dissipation in the input circuits and should be avoided?

Talking about Hi-Z, it usualy applies to outputs, CMOS inputs are allways
Hi-Z and this is not the topic of this discussion.

The output is connected to an input somewhere, or else we would not
care about what state it is in and would not be talking about it.

In many cases, the whole reason the output has tristate capability
is that it shares a pin with an input to the same chip and can never
be disconnected from it.

 

[R.Legg]

Because "average cross-sectional area" is useless here; it tells you
nothing about the actual thermal resistance. Especially when the
actual equation is right there.

I guess it's not just angles that can be obtuse. Piece-wise linear
approximation has been used for thousands of years - even your
plumbing example depended upon it. It's often the easiest way to
explain or to prove a mathematical expression. A rule of thumb is only
useful if it's easy to remember and apply in practical situations.

I may be wrong. Perhaps you have a different perspective to offer,
with some ball-park numbers. Please don't use plumbing analogies,
these only go so far before you have to do things like relate delta T
to water velocity - if you have to, use current flow in conductors.

My point was that averaging areas makes no sense, for any kind of
flow. Why ballpark when you can have the real thing?

Are you actually trying to say that a calculation makes no sense, that
a measurement is better?

I think they both have their places, particularly where economy of
time and materials is a concern. A calculation is intended to allow
you to avoid the trouble of having to re-invent the wheel, every time
you want to use one. A rule of thumb is intended to allow you to apply
a formula's result without having to derive and prove it each time
it's needed.

From all your many measurements, in permafrost or otherwise, have you
developed no general understanding that could have been passed on
succinctly to Ziguy? It appears that he 'left the biulding' about 4
days ago.

RL

 

[Genejocky]

Thank you h
Good to put another question to bed so to speak

Gene

"h" <h@howiem.dontspam.meee.com> wrote in message news:<3f2a5050$0$25427$afc38c87@news.easynet.co.uk>...

"Genejocky" <genejocky2000@yahoo.com> wrote in message
news:5b42948.0307312307.162f058b@posting.google.com...
It doesn't sound like anyone is doing anything too nice.

I've benn meaning to ask before having wondered for some time...
.. what does ">lbwgunderniyepowqmjpjeckgrfezudxkwdfxlnjn" mean??
Soory if it's a ignorant question :-(
Gene

AIUI mass-mailer programs will optionally add a random string of crap to
each spam sent in order to bypass spam-filters that rely on hashing. Stops
the big ISPs from being able to identify and remove spam easily.

h

 

[Genejocky]

I hadn't tried ensuring that I used a twisted pair... totally logical though.
Thank you Lord Garth

Ken,
Why do you say "bad Idea"?


Gene



Ken <___ken3@telia.com> wrote in message news:<pv7kiv4micf8g3daill1etaprp3ov5u8p2@4ax.com>...

On 31 Jul 2003 23:54:14 -0700, genejocky2000@yahoo.com (Genejocky)
wrote:


I am currently running a printer via usb cable.
I'd like to opperate the printer in another room from the pc.
The total length of the cable should still fall within the maximum
length allowed for the usb specification.
The plan is to create 2 cables by cutting the current usb-A to usb-B
cable in half.
A RJ45 connector is to be attached to each "cut end" to allow the pc
to connect to the usb cable- to the rj45 connector- to the cat5e cable
behind a wall plate- to the other end of the cat5e cable/wall plate in
the other room- to a RJ45 connector- to the 2nd half of the cut
printer cable- to the printer.

Bad idea.

 

[John Popelish]

nws wrote:

I've seen in a datasheet of some device, I think it was one of
the pic micro controlers, that I should use either a 2.2uF
tantalum capacitor or a 10uF electrolitic capacitor. Why with
tantalum lower values would still be ok ?

What counts is the impedance at some critical frequency (or band of
frequencies) involved in the operation of the chip. Aluminum
electrolytics tend to have a bit more internal series resistance and
inductance than a similar sized tantalum. (Aluminum capacitors
contain a roll of aluminum foil, while the tantalums have a brick of
tantalum sponge.) So the tantalum can have a little lower capacitance
and still have a lower impedance over the frequency range in
question. If you look up the data sheet for the caps, this shows up
in the minimum impedance spec or the self resonant frequency spec.

--
John Popelish

 

[Winfield Hill]

David Harmon wrote...

Please explain to me why this is not a really bad idea... My
understanding is that holding CMOS inputs at V/2 can cause large
power dissipation in the input circuits and should be avoided?

That's because both the upper p-type MOSFET device and the lower
n-type device are on, so current flows directly from one supply
rail to the other through these two FETs. Normally if the logic
input is close to either the top or bottom rail, one device is on
and the other off, so very little rail-to-rail current flows.

Thanks,
- Win

 

[Ken Taylor]

"Jim Thompson" <Jim-T@analog_innovations.com> wrote in message
newss9iiv4sule035mm2jis8q2i2cr3gfp6nd@4ax.com...

On Thu, 31 Jul 2003 02:20:30 +0000 (UTC), nbrbkk@doit.wisc.edu wrote:

Hidden cam pics of my hot neighbor tanning nude, download them.
lbwgunderniyepowqmjpjeckgrfezudxkwdfxlnjn

Anybody at U of W that can seek this twerp out and adjust his
attitude? Maybe stuff his head up a cow's ass ?

...Jim Thompson
--

I never met 'Jay Davis' in my old days at UW. I assume his PC has gotten a
virus.

Ken

 

[Kevin Aylward]

dan williams wrote:

Step 5) missing essentials...

When the power switch turns off, before the output diode engauges,
there's a really big voltage spike on the coil 'o wire. quite capable
of destroying the mosfet. so we add something across (debatable) the
coil to catch the spikes, there are the various types, used in
various times.

snubber ---/\/\/\---||-----

soft clamp ----->|----\/\/\/------
| |
----||----

and Zener clamp ----->|-----Z<----

I know that national designs always use zener clamps, I also know
that every other smps I have seen uses a soft clamp. (computer
supplies, computer monitors (the guys get annoyed with me continiously
disassembing the computers "Yup, see, thats a soft clamp too", "put it
back togethor, I need to check my email!" ), industrial supplies,
printers, VCR's)

snubbers always dissipate power, so I'll slide them aside...

Zener's are used to limit voltage, soft clamps and snubbers to
limit voltage and dv/dt, which will break down switches given enough.

The "soft clamp" shown i.e. the one with the diode-R-C is not (usually)
there to reduce the effects of leakage inductance spikes. It is used to
set a clamp voltage that resets the flux in the core and prevents
flux/current walking/ramping to to ET/N offsets.

Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Roger Johansson]

Winfield Hill <whill@picovolt.com> wrote:

Please explain to me why this is not a really bad idea... My
understanding is that holding CMOS inputs at V/2 can cause large
power dissipation in the input circuits and should be avoided?

That's because both the upper p-type MOSFET device and the lower
n-type device are on, so current flows directly from one supply
rail to the other through these two FETs. Normally if the logic
input is close to either the top or bottom rail, one device is on
and the other off, so very little rail-to-rail current flows.

But trying to hold the output at Vc/2 through a 100k resistor cannot
cause these problems.
Only if the output is held there by its input do we have to fear any
damage.


--
Roger J.

 

[Winfield Hill]

Roger wrote...

Winfield wrote:

Please explain to me why this is not a really bad idea... My
understanding is that holding CMOS inputs at V/2 can cause large
power dissipation in the input circuits and should be avoided?

That's because both the upper p-type MOSFET device and the lower
n-type device are on, so current flows directly from one supply
rail to the other through these two FETs. Normally if the logic
input is close to either the top or bottom rail, one device is on
and the other off, so very little rail-to-rail current flows.

But trying to hold the output at Vc/2 through a 100k resistor
cannot cause these problems. Only if the output is held there
by its input do we have to fear any damage.

What in the world do you mean? The excessive supply rail-to-rail
current will flow if both input devices are on, no matter what
means was used to get them in that state (they have no knowledge
of that, of course). If the P and N devices are identical, which
is the goal of the IC designer, then holding the input at Vdd/2 is
a good way of insure high fault current. Not the best way to get
a maximum current (floating the input is a good way), but something
that can certainly cause serious problems in some chips.

BTW, I said nothing about input currents or effects. Effective
input capacitance goes up dramatically when the input FETs are in
the linear region (Miller effect), but there's no other serious
effect, and the inputs still appear as high impedances.

WRT the output stages, if the input stage is in an uncontrolled
mid-bias class-A region, the output stage may also get into that
same state, and this can mean very high rail-to-rail currents and
dramatic heating and possible damage to the chip. It's true that
for this to happen a delicate balance is required, which isn't too
likely for most parts, but can't be ruled out. Feedback from the
output to the input (e.g. leakage to an open input, etc.) can help
insure that maximum current flows. Is that what you had in mind?
My point is that feedback isn't a requirement to get into trouble.

Thanks,
- Win

 

[Roger Johansson]

"Ban" <bansuri@web.de> wrote:

The poster states specifically state of *IOs*,
further he states he want to test with an oscilloscope.

So I think Win's warning about Vcc/2 *is* valid. Good if he mentions it,
because you do not seem to know this issue (as I didn't either to be honest)

Okay, I thought we were only talking about outputs.
When it is about in/output pins I agree.

--
Roger J.

 

[Roger Johansson]

I took a look at the docs for an AVR processor.

Its port pins can be in one of 4 states:
Low, High, Hi-Z input, Pulled up input.

There is a schmitt-trigger on the input so it will not be hurt by a
test as suggested where we from the outside apply a voltage Vc/2
through a 10-100k resistor.

If other microprocessors are made in less protected ways there could
be a problem of course, but the use of schmitt-trigger on the input
seems natural.

The output stage can hardly be damaged no matter if it is in low, high
or hi-Z state.

--
Roger J.