Driver to drive?

[geoff]

"yaputya" <yaputya.leftlegin@gmail.com> wrote in message
news:an5lgkFio63U1@mid.individual.net...

No all of us are on the Metric system..
Jamie

Then you must live in one of the following countries...U.S.A...
Liberia...Myanmar.

If you live in the US and don't work in a technical field then you are
probably just
ignorant of the real extent of metrification. The unit of temperature is
just the lowest
common denominator in the sensible (metric) units vs. silly (US/Imperial)
units
debate which was won a long time ago by near universal consensus. (Except
for the
obstinate and stupid trio of the U.S.A., Liberia and Myanmar)

Um I think the poms are at least still partially stuck in the imperial
dark-ages too.

geoff

 

[Joerg]

For a tester project I need a DDS source, should be a module but with
some decent output power and if possible a display. SPI or RS232 style
control would be nice. So far I only found this kind:

http://www.amazon.com/SG1005-Signal-Generator-Source-Function/dp/B008N7M5KU/ref=sr_1_1?ie=UTF8&qid=1359855256&sr=8-1&keywords=SG1005+DDS

Some comments are not so enthusing though:
http://www.elecfreaks.com/279.html

Can't find a manual for it or any decent info. Does anyone know where,
or has a suggestion for a better module? Need 10kHz to 1MHz (higher
would be nice) range, 2Vrms or so sine wave into a 50ohms load. Price is
not so important, can be $100/module.

Hacking is no problem, for example to get around a RS232/USB chip
because I can't really use USB. Sine wave quality doesn't have to be
super stellar, slight distortion would be ok. But I can't use a big boxy
function generator since it has to be integrated in the tester.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Jeff Liebermann]

On Fri, 1 Feb 2013 03:05:43 -0800 (PST), RealInfo
<therightinfo@gmail.com> wrote:

What is the "right" total amplification factor of an IF amplifiers chain in a radio receiver ?

For example a receiver employs 4 IF amps cascade , what is the proper total
voltage amplification of that IF cascade ?

IF? Whazzat? Everything I see and do is either direct conversion
(zero Hz IF), software defined radio (digital everything), or TRF
(tuned RF for instruments). Even the common AM/FM broadcast band
radios are now all digital.

Well, I guess I can make a rough estimate.

You probably want to hear signals down to about -110dBm. Your
earphone probably wants about 100mw into 32 ohms or about +20dBm into
50 ohms.
Power_gain = +20dBm - -110dBm = 130db
Of course, that only works if both the input and output impedances are
50 ohms. Converted to voltages
+20dBm @ 50 ohms = 2.25Vrms
-110dBm @ 50 ohms = 710uVrms
Voltage_gain = 2.25 / 710*10^-6 = 3170
Well, that's not exactly the IF voltage gain, but more like the system
gain. Each stage along the RF->IF->Audio path has either gain
(amplifiers, active mixers) or loss (passive mixers, filters,
demodulators). Each stage also has a finite limit as to how much
signal it can handle without clipping, distorting, or catching fire.
If your boss or instructor has an interest in dynamic range, then your
task is to distribute this 130dB of gain in such as way that you have
sufficient sensitivity (mostly controlled by the front end RF or IF
stage NF and gain), without overload. In this case, the ideal maximum
dynamic range design is when all the stages overload or distort at the
same RF input level.

Of course, this is a gross simplification. For example, if you're
demodulating FM, you will want additional IF gain to take advantage of
IF impulse noise clipping and AM rejection, and provide for noise
squelching. The design really depends on what you're trying to
accomplish, which you haven't bothered to specify or explain.

JDC recommended HP AppCAD for doing the calculations. I agree.
<http://www.hp.woodshot.com>
See the
Signals-Systems -> NoiseCalc
page. This is what it looks like:
<http://802.11junk.com/jeffl/crud/HP-AppCAD-NoiseCalc.jpg>

Good luck.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[John Doe]

Correct me if I'm wrong on any of this, but... The motion sensor
(part) output constantly varies. Only when its output reaches a
certain level relative to its normal state, then it trips a switch
that drives the light for some period of time. Then the lightbulb
switches off and waits for another significant change in
detection.

What I would like to do is have a lightbulb or LED
brightness/intensity follow the motion sensor output part. In
other words... If a bird flies by, the lightbulb would momentarily
dimly light. If a person walks into close range, the lightbulb
would continuously shine brightly. If the person walked behind
some object, the lightbulb would go off, and then when they
reappeared, the lightbulb would come back on. Hopefully I'm not
over describing this, but I'll be happy to provide more
description if asked.

Does such a device (or close) already exist for purchase in a
store?

The sensor output part typically could not be connected to an LED
without putting an amplifier on it? Anybody do this before, any
schematic?

Thanks.





--
Crossposted, feel free to delete the other group(s).
BTW. I'm not suggesting that anybody else could use or enjoy this.

 

[langwadt@fonz.dk]

On Feb 3, 4:00 am, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

Jasen Betts wrote:
On 2013-02-01, Robert Macy <robert.a.m...@gmail.com> wrote:

First place I'd look...
Electronic ballasts require an EMI filter in front of them to prevent
the conducted emanations. What you have there is a capacitor across
the AC mains followed by some husky inductance. That makes the load
look incredibly inductive, not capacitive - with main impact as you
turn it off. To envision, simply unplug your PC very slowly from the
AC outlet. Even with it turned off, you'll draw an impressive arc. All
due to the stored energy in the EMI filter. I suspect it is THAT
energy that is welding the contacts together.

contacts can't weld closed while they are open.
therfore the damage is occurring when they close
capacitor derived surge current through the bouncing
contacts heats them up to melting and the weld closed.

  They most certainly can weld together while they are in
the process of opening with induction loads. Which is why
special designs are out there just for handling induction
loads.

I have hard time seeing how it can happen when opening, arc
start when they are already moving apart so unless you close them
instantly after being melted by the opening arc I don't see how
they could weld

at closing it is more like spot welding, melt and press together

   If you don't use the correct contact design for these types
of loads, the relay will not last long.

Jamie

sure arcing at opening will eat the contacts, but that is different


-Lasse

 

On Sat, 2 Feb 2013 17:52:05 -0800 (PST), "dcaster@krl.org"
<dcaster@krl.org> wrote:

On Feb 2, 12:38 pm, k...@attt.bizz wrote:

One does not have to speech English to contribute.

Reality says otherwise.

Not really.

Yes, really, though I understand that the concept is entirely foreign
to you.

 

[John Doe]

Correct me if I'm wrong on any of this, but... The motion sensor
(part) output constantly varies. Only when its output reaches a
certain level relative to its normal state, then it trips a switch
that drives the light for some period of time. Then the lightbulb
switches off and waits for another significant change in
detection.

What I would like to do is have a lightbulb or LED
brightness/intensity follow the motion sensor output part. In
other words... If a bird flies by, the lightbulb would momentarily
dimly light. If a person walks into close range, the lightbulb
would continuously shine brightly. If the person walked behind
some object, the lightbulb would go off, and then when they
reappeared, the lightbulb would come back on. Hopefully I'm not
over describing this, but I'll be happy to provide more
description if asked.

Does such a device (or close) already exist for purchase in a
store?

The sensor output part typically could not be connected to an LED
without putting an amplifier on it? Anybody do this before, any
schematic?

Thanks.





--
Crossposted, feel free to delete the other group(s).
BTW. I'm not suggesting that anybody else could use or enjoy this.

 

[Jamie]

langwadt@fonz.dk wrote:

On Feb 3, 4:00 am, Jamie
jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

Jasen Betts wrote:

On 2013-02-01, Robert Macy <robert.a.m...@gmail.com> wrote:

First place I'd look...
Electronic ballasts require an EMI filter in front of them to prevent
the conducted emanations. What you have there is a capacitor across
the AC mains followed by some husky inductance. That makes the load
look incredibly inductive, not capacitive - with main impact as you
turn it off. To envision, simply unplug your PC very slowly from the
AC outlet. Even with it turned off, you'll draw an impressive arc. All
due to the stored energy in the EMI filter. I suspect it is THAT
energy that is welding the contacts together.

contacts can't weld closed while they are open.
therfore the damage is occurring when they close
capacitor derived surge current through the bouncing
contacts heats them up to melting and the weld closed.

They most certainly can weld together while they are in
the process of opening with induction loads. Which is why
special designs are out there just for handling induction
loads.



I have hard time seeing how it can happen when opening, arc
start when they are already moving apart so unless you close them
instantly after being melted by the opening arc I don't see how
they could weld

at closing it is more like spot welding, melt and press together


If you don't use the correct contact design for these types
of loads, the relay will not last long.

Jamie


sure arcing at opening will eat the contacts, but that is different


-Lasse

Many relay designs do a lot of surface sliding while they are pulling
apart or coming together. The pulling apart is worse because you are
increasing R as you do this. Since the arc has already started before
the R gets too high, plasma burn is already in the process and heating
is severe. When closing the contacts, you get only the initial bounce
and if the load is inductive, the contacts will most likely be closed
before enough energy is store to cause critical damage.

Simply put, you get a lot more plasma burn on the surface while
contacts are opening because the initial plasma has started while the
contacts where still touching but under a load and arcing, this
generates a malted metal vapor cloud which is highly conductive and
perpetuates the process. If the contacts have enough damage to them
already over time from doing this, the contacts will be pitted and
carbonized and at some point, the next plasma burn it goes through will
weld them. Repetitive action on the contacts will heat them
and they will weld anyway, most likely from incorrect use of the device.

Induction loads just makes things much worse because they can arc at
greater distances when opening and cause more damage.

Relays with spring arms are known for this kind of damage in the wrong
environment. You need contact designs that pull and push straight and
fast. Some have rounded heads to help vent off the metallic vapor along
with using tungsten, etc..

We have discharge contacts we use for draining off HV in the 20KV or
more range, from doing HI-POT test on large cables that can hold a large
charge. These units have 2 round balls that come
together that form the contact to ground and a air supply that blows
fresh air across the surface area. These units have been in service for
years and have never been replace as far as I know.


Jamie

 

[josephkk]

On Thu, 31 Jan 2013 20:33:44 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 1/31/2013 8:15 PM, Joerg wrote:
Artemus wrote:
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:510B09C0.6010200@electrooptical.net...
I have an application where I need to range switch between 1G and 50G feedback
resistors in a TIA for a capacitively coupled surface voltage probe. (I'm selling
the customer a fancy high-Z bootstrap amp as well, but they want an improved TIA as
a first step.)

I'm looking at using relays, of course, but there's an interesting wrinkle: I have
to short out the 1G resistor when it's in 50G mode, because otherwise the Johnson
noise of the 1G will couple through the relay contact capacitance and dominate the
noise above a few kHz.

Sooo, I'm taking a good look at some small relays. The best ones so far are the
Omron G6K ones, but even those are dominated by capacitance between coil and
contacts--the main capacitive coupling goes

open contact -> coil -> (closed contact + pole)

(it's about 0.6 pF each -> 0.3 pF total).

It looks as though I'll have to figure out a way to bootstrap the relay coil, or
else use a reed relay and a big external magnet.

Any better ideas?

Cheers

Phil Hobbs


Use a latching relay with both ends of the coil(s) driven by open
collector drivers?
Art


Good idea but those are mostly a few pF as well. Since fiberoptics guys
like Phil always have high voltages for photodiode biasing available,
how about taking Art's idea one step further: Drive both ends of the
latching relay coil through diodes and when it has switched over
reverse-bias them. That can get you down to fractions of a pF. If
suitable latching relays can be found, which may not be very trivial.


Thanks. Fractional picofarads are always a challenge since the
self-capacitance of a small but macroscopic object is down in that
range--the self-capacitance of a 1 cm radius sphere is 1.12 pF. In this
instance I have to bootstrap away a few picofarads worth of
probe-to-shield capacitance, so another half a pF or so isn't such a big
hit. It's more about trying to make it work in both the 1G and 50G
modes. (Fun.) I'm tempted to use a reed switch and the guts of a
dishwasher solenoid, but it has to Look Professional. (tm)

Cheers

Phil Hobbs

There are more modest RF relays, still not all that small.

See:

http://www.greenstoneusa.com/vacuumrelays.htm

Maybe http://www.omron.com/ecb/products/pry/111/g5v_2.html

Finding much of anything for this is a bit challenging. The search
engines do not cooperate.

?-)

 

[josephkk]

On Fri, 01 Feb 2013 16:01:26 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 02/01/2013 03:52 PM, Joerg wrote:
Phil Hobbs wrote:
On 02/01/2013 03:29 PM, langwadt@fonz.dk wrote:
On Feb 1, 7:08 pm, Phil Hobbs<pcdhSpamMeSensel...@electrooptical.net
wrote:
On 02/01/2013 09:33 AM, Phil Hobbs wrote:







On 2/1/2013 9:20 AM, langw...@fonz.dk wrote:
On Feb 1, 2:11 pm, brent<buleg...@columbus.rr.com> wrote:
On Jan 31, 7:18 pm, Phil Hobbs

pcdhSpamMeSensel...@electrooptical.net> wrote:
I have an application where I need to range switch between 1G and
50G
feedback resistors in a TIA for a capacitively coupled surface
voltage
probe. (I'm selling the customer a fancy high-Z bootstrap amp as
well,
but they want an improved TIA as a first step.)

I'm looking at using relays, of course, but there's an interesting
wrinkle: I have to short out the 1G resistor when it's in 50G mode,
because otherwise the Johnson noise of the 1G will couple through
the
relay contact capacitance and dominate the noise above a few kHz.

Sooo, I'm taking a good look at some small relays. The best ones
so far
are the Omron G6K ones, but even those are dominated by capacitance
between coil and contacts--the main capacitive coupling goes

open contact -> coil -> (closed contact + pole)

(it's about 0.6 pF each -> 0.3 pF total).

It looks as though I'll have to figure out a way to bootstrap the
relay
coil, or else use a reed relay and a big external magnet.

Any better ideas?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot nethttp://electrooptical.net

IJust out of curiosity.... Why did you call your thread RF relay? I
am missing the RF relay part in your text. I looked up the Omron G6K
which you referenced and it does not strike me as an RF relay.

This is what I think of when I think RF relay:

http://www.rfrelaystore.com/

there a different kinds of g6k

http://downloads.components.omron.eu/OCB/Products/Relays/High%20Frequ...


-Lasse

Yeah, I should get some of those to test as well. Thanks.

Cheers

Phil Hobbs

The ones I tested are G6KU-2G-Y.

The section-to-section capacitance goes from 300 fF to 60 fF when I
ground the coil, but the open-contact capacitance only goes from 410 to
200 fF, so I guess the actual open-contact capacitance is about 0.2 pF.
That isn't horrible--just the resistors will be in that ballpark.


first hit on google for low capicity is something like
http://www.pickeringrelay.com/pdfs/103.pdf how does that compare?

We use some HF3 relays, it's an RF relay no idea what capacitances
are
but you can get one is latching maybe that will help ?


-Lasse

That's about the same, quoting 100 fF across the open contacts. That's
less than half the coil-contact capacitance, so they must be grounding
the coil to make that measurement.

The self-capacitance is of that order as well, so there's a limit to
what one can expect to do by shrinking stuff.


They make one with a guard ring around the coil.


Thanks, I saw that. They said that the ones without the guard ring had
lower capacitance, though. Grounding or bootstrapping the coil isn't
too difficult, so that's a win.

I'll probably either stick with the G6KU ones I have, or go with the new
Panasonic ones Fred found. I'll get a few of them to test.

Cheers

Phil Hobbs

Hmmm. Ya know, it may not be practical to do this "on board". When
resistances exceed 1Gohm the board conductances may swamp things. You
have been around this block many times before though, i would like to know
what board material you use if this is all on board. Just some things i
saw when i took the covers of a Keithley 619 that had problems before we
sent it to the cal/repair lab. It was a bit strange from a operator or a
programmers POV (i had both) but otherwise a very nice instrument.

?-)

 

[josephkk]

On Fri, 01 Feb 2013 10:14:48 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

brent wrote:

On Jan 31, 7:18 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
I have an application where I need to range switch between 1G and 50G
feedback resistors in a TIA for a capacitively coupled surface voltage
probe. (I'm selling the customer a fancy high-Z bootstrap amp as well,
but they want an improved TIA as a first step.)

I'm looking at using relays, of course, but there's an interesting
wrinkle: I have to short out the 1G resistor when it's in 50G mode,
because otherwise the Johnson noise of the 1G will couple through the
relay contact capacitance and dominate the noise above a few kHz.

Sooo, I'm taking a good look at some small relays. The best ones so far
are the Omron G6K ones, but even those are dominated by capacitance
between coil and contacts--the main capacitive coupling goes

open contact -> coil -> (closed contact + pole)

(it's about 0.6 pF each -> 0.3 pF total).

It looks as though I'll have to figure out a way to bootstrap the relay
coil, or else use a reed relay and a big external magnet.

Any better ideas?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot nethttp://electrooptical.net

IJust out of curiosity.... Why did you call your thread RF relay? I
am missing the RF relay part in your text. I looked up the Omron G6K
which you referenced and it does not strike me as an RF relay.

This is what I think of when I think RF relay:

http://www.rfrelaystore.com/


Those are OK for low power. Try switching in the 1 KW to 500 KW RF
range with one.

Fine. You made your point, and i agree. The relays i saw in a mere 1 kW
HF transmitter were much larger (about 5/8 diameter by 3 inches spdt). It
is possible that such relays may be useful for Phil Hobbs needs. The
questions involved are shunt conductance and capacitance.

?-)

 

[Tim Williams]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
newseadnYm8hbnadZDMnZ2dnUVZ_qSdnZ2d@earthlink.com...

I have hard time seeing how it can happen when opening, arc
start when they are already moving apart so unless you close them
instantly after being melted by the opening arc I don't see how
they could weld

at closing it is more like spot welding, melt and press together

If you don't use the correct contact design for these types
of loads, the relay will not last long.

Jamie

sure arcing at opening will eat the contacts, but that is different


You've never done any arc welding, have you?

All the times I've stuck the rod to the work were exclusively when closing
the circuit. I can safely say I have never, ever had a rod stick to the
work when pulling it off!

Tim

--
Deep Friar: a very philosophical monk.
Website: http://www.seventransistorlabs.com/

 

[John Doe]

Correct me if I'm wrong on any of this, but... The motion sensor
(part) output constantly varies. Only when its output reaches a
certain level relative to its normal state, then it trips a switch
that drives the light for some period of time. Then the lightbulb
switches off and waits for another significant change in
detection.

What I would like to do is have a lightbulb or LED
brightness/intensity follow the motion sensor output part. In
other words... If a bird flies by, the lightbulb would momentarily
dimly light. If a person walks into close range, the lightbulb
would continuously shine brightly. If the person walked behind
some object, the lightbulb would go off, and then when they
reappeared, the lightbulb would come back on. Hopefully I'm not
over describing this, but I'll be happy to provide more
description if asked.

Does such a device (or close) already exist for purchase in a
store?

The sensor output part typically could not be connected to an LED
without putting an amplifier on it? Anybody do this before, any
schematic?

Thanks.





--
Crossposted, feel free to delete the other group(s).
BTW. I'm not suggesting that anybody else could use or enjoy this.

 

[Phil Allison]

"miso"

** The heading applies to fuckwit scumbags like you too.

ASD fucked, trolling morons have no right to live.

You need a bullet.

 

[Michael A. Terrell]

josephkk wrote:

On Fri, 01 Feb 2013 10:14:48 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


brent wrote:

On Jan 31, 7:18 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
I have an application where I need to range switch between 1G and 50G
feedback resistors in a TIA for a capacitively coupled surface voltage
probe. (I'm selling the customer a fancy high-Z bootstrap amp as well,
but they want an improved TIA as a first step.)

I'm looking at using relays, of course, but there's an interesting
wrinkle: I have to short out the 1G resistor when it's in 50G mode,
because otherwise the Johnson noise of the 1G will couple through the
relay contact capacitance and dominate the noise above a few kHz.

Sooo, I'm taking a good look at some small relays. The best ones so far
are the Omron G6K ones, but even those are dominated by capacitance
between coil and contacts--the main capacitive coupling goes

open contact -> coil -> (closed contact + pole)

(it's about 0.6 pF each -> 0.3 pF total).

It looks as though I'll have to figure out a way to bootstrap the relay
coil, or else use a reed relay and a big external magnet.

Any better ideas?

Cheers

Phil Hobbs

IJust out of curiosity.... Why did you call your thread RF relay? I
am missing the RF relay part in your text. I looked up the Omron G6K
which you referenced and it does not strike me as an RF relay.

This is what I think of when I think RF relay:

http://www.rfrelaystore.com/

Those are OK for low power. Try switching in the 1 KW to 500 KW RF
range with one.

Fine. You made your point, and I agree. The relays i saw in a mere 1 kW
HF transmitter were much larger (about 5/8 diameter by 3 inches spdt). It
is possible that such relays may be useful for Phil Hobbs needs. The
questions involved are shunt conductance and capacitance.

At 5 KW & up they don't even try to use RF relays at a lot of sites.
They use multi pole power contactors typically used for 240 or three
phase power at similar levels. They are usually mounted in the center
of a large sheet of 1/4" or thicker Phenolic to both reduce capacitance
& arcing.

Some use solid copper busboys & servo motors, like the old VOA site
in Bethany Ohio. For those applications there were no off the shelf
relays on the market.

Phil does come up with some fairly uniqe needs, but he seems to find
answers for them.

 

[John Devereux]

Jeroen <jeroen@nospam.please> writes:

On 2013-02-02 18:20, Michael A. Terrell wrote:

"dcaster@krl.org" wrote:

On Feb 2, 12:08 am, k...@attt.bizz wrote:

If they're here legally, there isn't much that can be done. If
they're wanting to come here or even wanting a work permit, they
should be fluent in English. It only makes sense. There certainly
isn't a shortage of people who want to immigrate. Take only those who
will contribute. We have enough takers, already.

One does not have to speech English to contribute.


"Not have to speech"?

Anyone who doesn't speak the common language wastes resources that
could be used for other needs.

Come one Michael, give him a break. Mastering a language perfectly is
not that easy, even for natives. Just a few articles ago, you yourself
wrote : "I had to wait in line behind someone from Jamaica that....",
which may be common, but it's still wrong.

(I wonder how many errors I made in these few lines... Fire away!)

"Come one" ?

Funny how that always happens...


--

John Devereux

 

[Uncle Steve]

On Sat, Feb 02, 2013 at 08:48:41PM -0500, Bob Engelhardt wrote:

On 2/2/2013 11:09 AM, Uncle Steve wrote:
When I've properly broken in my new drivers I'll make a youtube video
so you can hear the results for yourself....

No emoticon, so I assume that he's serious. In which case, even though
I know nothing about what he's talking about, I do know that he is full
of shit. Youtube ... gimme a break!!! Bob

It was a joke, but several people were bound to mistake it for a
serious proposition.

Perhaps I will make a youtube video and see what people say.


Regards,

Uncle Steve

--
More than a century has passed since science laid down sound
propositions as to the origins of the universe, but how many have
mastered them or possess the really scientific spirit of criticism? A
few thousands at the outside, who are lost in the midst of hundreds of
millions still steeped in prejudices and superstitions worthy of
savages, who are consequently ever ready to serve as puppets for
religious impostors. -- Peter Kropotkin

 

[Mark Zenier]

In article <keku69$6s1$1@dont-email.me>,
Tim Williams <tmoranwms@charter.net> wrote:

AFAIK, pyroelectric sensors are a "single pixel" sort of thing, so they
don't know if the scene is moving, only if the average IR changes. Which it
does when someone comes into view or jumps out of the shadows, but it
doesn't do jack if someone walks around freely while holding up a
room-temperature blanket, or moves in the scene while presenting an equal
viewing cross section (probably tricky to do).

They're two "pixels" in an AC coupled differential circuit.
The optics are set so that the sensors see adjacent areas and
react to fast changes. (You can fool them if you move real slow).

The best analogy of the optics is to spread your fingers apart and put the
flat of your palms together so that the fingers interleave. One sensor
per "hand", with the views of the two sensors interlinked. Any movement
quick enough, and one sensor will decrease while the other increases.
The response is usually flat in one plane, determined by the way the
plastic lens is molded.

Radio-Electronics/Electronic Now magazine had a long distance pyroelectric
sensor project that used a motor driven mechanical chopper, back when
these things were new.

Mark Zenier mzenier@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)

 

[mike]

On 2/3/2013 5:51 PM, John Doe wrote:

John Fields<jfields austininstruments.com> wrote:

John Doe<jdoe usenetlove.invalid> wrote:

Correct me if I'm wrong on any of this, but... The motion sensor
(part) output constantly varies.

Generally, no.

The common pyroelectric motion sensor outputs a single pulse
when the incident radiation which falls on the detector has a
higher or lower wavelength than that of the ambient radiation
within the field of view of the transducer.

I guess that means there is no analog output. So it's not like a
photo resistor. I've played with photo resistors, controlling a
variable frequency connected to a speaker. Aiming it towards a TV
produced amusing and rapidly changing frequencies. I wonder if
there are hypersensitive photo resistors that might do (with a
wide field of view), maybe infrared or whatever. Or maybe that has
already been suggested under different terminology.

Someone already mentioned a TOF SONAR sensor, which would be
ideal if it could resolve distance to the accuracy you require,
which will vary depending on temperature, humidity, and
atmospheric pressure.

Can you address that?

I don't need to know distance or speed. All I want to sense is
changes in radiation in the area. But if the changes in intensity
are great, that might suggest the object is either large or
nearby. I guess that would be a function of something like a
long-range omnidirectional (or wide angle, as long as it's view is
not narrow) infrared photo resistor/sensor if there is such a
thing. I'll look.

Distance to sense a person, to noticeably and distinctly change
the output, needs to be at least 20 feet, preferably 50-100.




https://www.google.com/search?num=100&hl=en&lr=&safe=images&tbo=d&as_qdr=all&q=xbox+motion+detection&oq=xbox+motion+detection&gs_l=serp.12..0j0i5i30l2j0i8i10i30j0i8i30l3.7907.7907.0.10998.1.1.0.0.0.0.934.934.6-1.1.0.les%3B..0.0...1c..2.serp.z6TfNc9RhwA

 

[John Doe]

To be clear...
actually, what I played with might be called a photodiode (not a
photoresistor), it looked like an ordinary white LED, it didn't have
the squiggly wires inside