Programing Port Impedance?
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Happy Friday to Everyone,
This request is directed toward Tracy in particular, but anyone with input
please do so.
Tracy - Would you be willing to elaborate, for those of us with few and
ailing brain cells, as to why lowering the input impedance of the serial
programing port makes it less sensitive to noise? It seems to my
electronically uneducated mind that higher impedance would equate to less
noise sensitivity and that lower impedance would mean more noise
sensitivity. I'll be the first to say that my electronic education is at
the novice level and most likely the answer to this question is found in
the basics that I haven't learned.
Thank You,
Tim
Timothy Medema
CrystaLite, Incorporated
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232
www.crystaliteinc.com
<mailto:timm@c...>timm@c...
The information transmitted is intended only for the person or entity to
whom it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you received
this in error, please contact the sender and delete the material from any
computer.
This request is directed toward Tracy in particular, but anyone with input
please do so.
Tracy - Would you be willing to elaborate, for those of us with few and
ailing brain cells, as to why lowering the input impedance of the serial
programing port makes it less sensitive to noise? It seems to my
electronically uneducated mind that higher impedance would equate to less
noise sensitivity and that lower impedance would mean more noise
sensitivity. I'll be the first to say that my electronic education is at
the novice level and most likely the answer to this question is found in
the basics that I haven't learned.
Thank You,
Tim
Timothy Medema
CrystaLite, Incorporated
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232
www.crystaliteinc.com
<mailto:timm@c...>timm@c...
The information transmitted is intended only for the person or entity to
whom it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you received
this in error, please contact the sender and delete the material from any
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Comments
>This request is directed toward Tracy in particular, but anyone with input
>please do so.
>Tracy - Would you be willing to elaborate, for those of us with few and
>ailing brain cells, as to why lowering the input impedance of the serial
>programing port makes it less sensitive to noise? It seems to my
>electronically uneducated mind that higher impedance would equate to less
>noise sensitivity and that lower impedance would mean more noise
>sensitivity. I'll be the first to say that my electronic education is at
>the novice level and most likely the answer to this question is found in
>the basics that I haven't learned.
>Thank You,
>Tim
>Timothy Medema
>CrystaLite, Incorporated
>3307 Cedar St. (425) 745-6000 800-666-6065
>Everett, WA 98201 Fax: (425) 257-0232
>www.crystaliteinc.com
><mailto:timm@c...>timm@c...
Sure. Part 1.
Say there is annoying noise in a room, but you want to hear one loud
sound, the dinner gong. If you put in an ear plug, that is like
putting a high impedance in series with your ear so the sound can't
get in. Maybe that is analogous what you are thinking of when you
equate high impedance with reduced noise sensitivity. The noise
would just bounce off the outside. The sound of the gong would
penetrate because it is so loud and low-pitched. Or instead of an
ear-plug that reflects the noise, you might use a sound absorbing
foam muff over your ears. The absorbing properties are like a low
impedance that drains off the sound energy before it reaches your
ear. That is more like what I am talking about with a low impedance.
As far as the effect on what you hear, the effect is the same, but
the mechanism is different, reflection versus absorption.
(Inside the ear there is a mechanism of small bones that transfers
the sound that hits the eardrum over to the hearing organ, and those
bones are an impedance matching device, to translate motions in air
over to motions in a fluid. Anything that happens in that mechanism
can and often does affect hearing, often affecting the high
frequencies first. I better stop there. Dennis O'leary may be
reading this, and that is his field! Impedance matching is
everywhere.)
In electrical terms it comes down to a voltage divider.
R1
Vin ---/\/\---o
Vout
|
;--/\/\-'
| R2
com --o
Vout = Vin * (R2/(R1+R2))
The voltage, Vout, at the output can be decreased either by
_increasing_ the value of the resistor R1, or by _decreasing_ the
value of the resistor R2. The same thing is true if there are
capacitors and inductors in the circuit, but then we would talk about
the impedance Z1 and the impedance Z2. The Z1 is a "series"
impedance and the Z2 is a "parallel" impedance.
To be continued...
types and RMS amplitudes generated as a function of input impedance.
But a simpler method is to think of input circuitry as an antenna: the
higher the impedance, the more sensitivity to stray RF input. You can
verify this experimentally by using an op amp (with itself having a high
input impedance) and comparing the noise at the output with 1) a 1K
resistor and 2) a 100K resistor at the + input, with - input grounded.
In each case, connect a resistor of the same value from the + input to
the output. View the output in each case on an oscilloscope, and
compare the 2 cases.
Dennis
Original Message
From: Timothy Medema [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=sk4O9AACMkA7KvpEb9OtocF3jzI6ERKM_rEqkQwMLx-rcGVPcOlySVdqv_LDPMYgkcOITPQWtzV46a_CpVY]timm@c...[/url
Sent: Friday, August 09, 2002 8:04 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Programing Port Impedance?
Happy Friday to Everyone,
This request is directed toward Tracy in particular, but anyone with
input
please do so.
Tracy - Would you be willing to elaborate, for those of us with few and
ailing brain cells, as to why lowering the input impedance of the serial
programing port makes it less sensitive to noise? It seems to my
electronically uneducated mind that higher impedance would equate to
less
noise sensitivity and that lower impedance would mean more noise
sensitivity. I'll be the first to say that my electronic education is
at
the novice level and most likely the answer to this question is found in
the basics that I haven't learned.
Thank You,
Tim
Timothy Medema
CrystaLite, Incorporated
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232
www.crystaliteinc.com
<mailto:timm@c...>timm@c...
The information transmitted is intended only for the person or entity to
whom it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you
received
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What a fantastic analogy! That's by far the best explanation of
impedance I've ever been given. You've put it into terms that even I can
begin to understand. A feat in and of itself. Thanks guys, for sharing
from the stores of your gray-matter.
Much Appreciated,
Tim
Timothy Medema
CrystaLite, Incorporated
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232
www.crystaliteinc.com
<mailto:timm@c...>timm@c...
The information transmitted is intended only for the person or entity to
whom it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you received
this in error, please contact the sender and delete the material from any
computer.
For Tracy - Looking forward to Part 2 if you get a chance.
Many Thanks,
Tim
At 11:15 AM 8/9/2002 -0700, you wrote:
> >Happy Friday to Everyone,
> >This request is directed toward Tracy in particular, but anyone with input
> >please do so.
> >Tracy - Would you be willing to elaborate, for those of us with few and
> >ailing brain cells, as to why lowering the input impedance of the serial
> >programing port makes it less sensitive to noise? It seems to my
> >electronically uneducated mind that higher impedance would equate to less
> >noise sensitivity and that lower impedance would mean more noise
> >sensitivity. I'll be the first to say that my electronic education is at
> >the novice level and most likely the answer to this question is found in
> >the basics that I haven't learned.
> >Thank You,
> >Tim
> >Timothy Medema
> >CrystaLite, Incorporated
> >3307 Cedar St. (425) 745-6000 800-666-6065
> >Everett, WA 98201 Fax: (425) 257-0232
> >www.crystaliteinc.com
> ><mailto:timm@c...>timm@c...
>
>
>Sure. Part 1.
>
>Say there is annoying noise in a room, but you want to hear one loud
>sound, the dinner gong. If you put in an ear plug, that is like
>putting a high impedance in series with your ear so the sound can't
>get in. Maybe that is analogous what you are thinking of when you
>equate high impedance with reduced noise sensitivity. The noise
>would just bounce off the outside. The sound of the gong would
>penetrate because it is so loud and low-pitched. Or instead of an
>ear-plug that reflects the noise, you might use a sound absorbing
>foam muff over your ears. The absorbing properties are like a low
>impedance that drains off the sound energy before it reaches your
>ear. That is more like what I am talking about with a low impedance.
>As far as the effect on what you hear, the effect is the same, but
>the mechanism is different, reflection versus absorption.
>
>(Inside the ear there is a mechanism of small bones that transfers
>the sound that hits the eardrum over to the hearing organ, and those
>bones are an impedance matching device, to translate motions in air
>over to motions in a fluid. Anything that happens in that mechanism
>can and often does affect hearing, often affecting the high
>frequencies first. I better stop there. Dennis O'leary may be
>reading this, and that is his field! Impedance matching is
>everywhere.)
>
>In electrical terms it comes down to a voltage divider.
>
> R1
> Vin ---/\/\---o
Vout
> |
> ;--/\/\-'
> | R2
> com --o
>
> Vout = Vin * (R2/(R1+R2))
>
>The voltage, Vout, at the output can be decreased either by
>_increasing_ the value of the resistor R1, or by _decreasing_ the
>value of the resistor R2. The same thing is true if there are
>capacitors and inductors in the circuit, but then we would talk about
>the impedance Z1 and the impedance Z2. The Z1 is a "series"
>impedance and the Z2 is a "parallel" impedance.
>
>To be continued...
>
>
>
>To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
>from the same email address that you subscribed. Text in the Subject and
>Body of the message will be ignored.
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Timothy Medema
CrystaLite, Incorporated
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232
www.crystaliteinc.com
<mailto:timm@c...>timm@c...
The information transmitted is intended only for the person or entity to
whom it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you received
this in error, please contact the sender and delete the material from any
computer.