newbie BS2 question
HI· all,·· I am· attempting· to measure the output· from· a Cadmium-Sulfide Photocell· that I purchased from Radio Shack.( pn276-1657 )· To the best of my ability,· I have· detemined· that it· puts· out· between 0-250mV· ( depending· on how much light is present )· I assume· that I will connect it to an output pin of my choice on the stamp...and· use· the RcTime·· command sort· of· like· how· it· is· used· with the· AD592·· analog· sensor· in· the stamp· tutorial on the Parallax web site.· Does· this· sound· like· I am on the right· track?· can· anyone think· of· any· circuitry· I will need· to complete· this?· ON the AD592· circuit· there· is· an· 100k· resistor· inline· from· the sensor· to 5+,· will· I need· this· for· a photocell?· My·· goal· is· to have a· sort of· accurate· measurement· tool· for sunlight· and· artificial· light.
any· ideas· and· thought· are· welcome
Dave
samhell@samhell.com
any· ideas· and· thought· are· welcome
Dave
samhell@samhell.com
Comments
Original Message
From: samhell@samhell.com
To: basicstamps@egroups.com
Sent: Sunday, April 09, 2000 12:29 AM
Subject: [noparse][[/noparse]basicstamps] [noparse][[/noparse]STAMPS]newbie BS2 question
HI· all,·· I am· attempting· to measure the output· from· a Cadmium-Sulfide Photocell· that I purchased from Radio Shack.( pn276-1657 )· To the best of my ability,· I have· detemined· that it· puts· out· between 0-250mV· ( depending· on how much light is present )· I assume· that I will connect it to an output pin of my choice on the stamp...and· use· the RcTime·· command sort· of· like· how· it· is· used· with the· AD592·· analog· sensor· in· the stamp· tutorial on the Parallax web site.· Does· this· sound· like· I am on the right· track?· can· anyone think· of· any· circuitry· I will need· to complete· this?· ON the AD592· circuit· there· is· an· 100k· resistor· inline· from· the sensor· to 5+,· will· I need· this· for· a photocell?· My·· goal· is· to have a· sort of· accurate· measurement· tool· for sunlight· and· artificial· light.
any· ideas· and· thought· are· welcome
Dave
samhell@samhell.com
any· ideas· and· thought· are·welcome
Dave
samhell@samhell.com
Dave,
Check Peter Anderson's site out.· He has several light sensors forsale.· Using cell above will not give you accurate lightreadings.· The parts Mr. Anderson lists on his site convert lightintensity to frequency.· Try one of them.· If I remember theywere less than 5.00.
Brian Gracia
********************************************
Better Produce through Better Control
********************************************
photoRESISTORS. They don't produce current or voltage, but a varying
resistance. Try this (from the Stamps In Class Robotics book):
VDD+
|
==== 0.01uf cap
220ohm |
o
/\/\/\/\/\---o
|
( CDS )
|
VSS-
-William
Original Message
From: <samhell@s...>
To: <basicstamps@egroups.com>
Sent: Sunday, April 09, 2000 12:29 AM
Subject: [noparse][[/noparse]basicstamps] [noparse][[/noparse]STAMPS]newbie BS2 question
HI all, I am attempting to measure the output from a Cadmium-Sulfide
Photocell that I purchased from Radio Shack.( pn276-1657 ) To the best of
my ability, I have detemined that it puts out between 0-250mV
depending on how much light is present ) I assume that I will connect it
to an output pin of my choice on the stamp...and use the RcTime command
sort of like how it is used with the AD592 analog sensor in the
stamp tutorial on the Parallax web site. Does this sound like I am on
the right track? can anyone think of any circuitry I will need to
complete this? ON the AD592 circuit there is an 100k resistor
inline from the sensor to 5+, will I need this for a photocell? My
goal is to have a sort of accurate measurement tool for sunlight and
artificial light.
any ideas and thought are welcome
Dave
samhell@s...
to 0 ohms so you should be OK with just the cell and a capacitor. You can
vary the range of measurements you get by changing the value of the
capacitor, so try several until you get a wide range of dark vs. light
readings. Or you can look at the RCTIME command, measure the max and min
resistance and figure a close value for the cap. The cell is not generating
voltage but it may be picking up 60Hz hum or otherwise rectifying noise.
Good luck.
Al Williams
AWC
*Floating point math for the Stamp, PIC, SX, or any microcontroller at
http://www.al-williams.com/awce/pak1.htm
Original Message
From: samhell@s... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=QSafx5D3zMWQEqJq_zCFjvrbPsZoXWIcvtKjrWVbhfRoFFX9wXVfyhWeldNXl2bNwdB4_W6g1BZ-JQZjWQ]samhell@s...[/url
Sent: Saturday, April 08, 2000 11:29 PM
To: basicstamps@egroups.com
Subject: [noparse][[/noparse]basicstamps] [noparse][[/noparse]STAMPS]newbie BS2 question
HI all, I am attempting to measure the output from a Cadmium-Sulfide
Photocell that I purchased from Radio Shack.( pn276-1657 ) To the best of
my ability, I have detemined that it puts out between 0-250mV
depending on how much light is present ) I assume that I will connect it
to an output pin of my choice on the stamp...and use the RcTime command
sort of like how it is used with the AD592 analog sensor in the
stamp tutorial on the Parallax web site. Does this sound like I am on
the right track? can anyone think of any circuitry I will need to
complete this? ON the AD592 circuit there is an 100k resistor
inline from the sensor to 5+, will I need this for a photocell? My
goal is to have a sort of accurate measurement tool for sunlight and
artificial light.
any ideas and thought are welcome
Dave
samhell@s...
Original Message
From: "William Cox" <william@c...>
To: <basicstamps@egroups.com>
Sent: Sunday, April 09, 2000 11:12 AM
Subject: Re: [noparse][[/noparse]basicstamps] [noparse][[/noparse]STAMPS]newbie BS2 question
> Actually (if you bought those CdS cells in the 5pack), they are
> photoRESISTORS. They don't produce current or voltage, but a varying
> resistance. Try this (from the Stamps In Class Robotics book):
>
> VDD+
> |
> ==== 0.01uf cap
> 220ohm |
> o
/\/\/\/\/\---o
> |
> ( CDS )
> |
> VSS-
>
> -William
>
>
Original Message
> From: <samhell@s...>
> To: <basicstamps@egroups.com>
> Sent: Sunday, April 09, 2000 12:29 AM
> Subject: [noparse][[/noparse]basicstamps] [noparse][[/noparse]STAMPS]newbie BS2 question
>
>
> HI all, I am attempting to ......................
of times they come out garbled, because people don't view them with a
standard with font. I hope this helped.
-William
____________________________
http://robot-central.webjump.com/
Robotics books, projects, resources,
links, news, and more!
··································································· Ray, N2FRA
Original Message
From: samhell@samhell.com <samhell@samhell.com>
To: basicstamps@egroups.com <basicstamps@egroups.com>
Date: Sunday, April 09, 2000 12:24 AM
Subject: [noparse][[/noparse]basicstamps] [noparse][[/noparse]STAMPS]newbie BS2 question
HI· all,·· I am· attempting· to measure the output· from· a Cadmium-Sulfide Photocell· that I purchased from Radio Shack.( pn276-1657 )· To the best of my ability,· I have· detemined· that it· puts· out· between 0-250mV· ( depending· on how much light is present )· I assume· that I will connect it to an output pin of my choice on the stamp...and· use· the RcTime·· command sort· of· like· how· it· is· used· with the· AD592·· analog· sensor· in· the stamp· tutorial on the Parallax web site.· Does· this· sound· like· I am on the right· track?· can· anyone think· of· any· circuitry· I will need· to complete· this?· ON the AD592· circuit· there· is· an· 100k· resistor· inline· from· the sensor· to 5+,· will· I need· this· for· a photocell?· My·· goal· is· to have a· sort of· accurate· measurement· tool· for sunlight· and· artificial· light.
any· ideas· and· thought· are· welcome
Dave
samhell@samhell.com
Cadmium-Sulfide
> Photocell that I purchased from Radio Shack.( pn276-1657 ) To the best
of
> my ability, I have detemined that it puts out between 0-250mV (
> depending on how much light is present ) I assume that I will connect
it
> to an output pin of my choice on the stamp...and use the RcTime
command
> sort of like how it is used with the AD592 analog sensor in
the
> stamp tutorial on the Parallax web site. Does this sound like I am
on
> the right track? can anyone think of any circuitry I will need to
> complete this? ON the AD592 circuit there is an 100k resistor
> inline from the sensor to 5+, will I need this for a photocell?
> My goal is to have a sort of accurate measurement tool for
sunlight
> and artificial light.
Which tutorial on the Parallax web site are you referring to? Are you sure
about the 100k resistor in series with the AD592? The following tutorial
(by yours truly) shows how to interface to the AD592 using RCtime:
http://www.stampsinclass.com/downloads/em3.pdf
And the following shows how to interface to photodiodes using RCtime:
http://www.stampsinclass.com/downloads/em4.pdf
Please qualify what you mean by "accurate measurement tool for sunlight
and artificial light". In practice, photodiodes are the most useful for
quantitative measurement, because of their range and linearity. The range
of light from indoor to outdoor is a couple of orders of magnitude. CdS
photocells are quite nonlinear, and thus difficult to calibrate. But CdS
would be fine if you just need repeatablility.
-- Tracy Allen
Electronically Monitored Ecosystems
http://www.emesystems.com
Tracy,
yes you are correct, I did not mean between 5+ and the AD592.
Which by the way can I ask you, which AD592 did you actually use for the
tutorial? the AD592AN, AD592BN, or maybe one more model ( Im not sure )
also, to answer your question, I just meant accurate to the degree of
"dark/dusk/cloudy/sunny/really bright" not so much individual lumens.
Anyway your tutorial is great...I ve really learned alot.
Dave
Original Message
From: Tracy Allen <emesys@c...>
To: INTERNET:basicstamps@egroups.com <basicstamps@egroups.com>
Date: Monday, April 10, 2000 2:25 AM
Subject: Re: [noparse][[/noparse]basicstamps] [noparse][[/noparse]STAMPS]newbie BS2 question
>> HI all, I am attempting to measure the output from a
>Cadmium-Sulfide
>> Photocell that I purchased from Radio Shack.( pn276-1657 ) To the best
>of
>> my ability, I have detemined that it puts out between 0-250mV (
>> depending on how much light is present ) I assume that I will connect
>it
>> to an output pin of my choice on the stamp...and use the RcTime
>command
>> sort of like how it is used with the AD592 analog sensor in
>the
>> stamp tutorial on the Parallax web site. Does this sound like I am
>on
>> the right track? can anyone think of any circuitry I will need to
>> complete this? ON the AD592 circuit there is an 100k resistor
>> inline from the sensor to 5+, will I need this for a photocell?
>> My goal is to have a sort of accurate measurement tool for
>sunlight
>> and artificial light.
>
>
>Which tutorial on the Parallax web site are you referring to? Are you sure
>about the 100k resistor in series with the AD592? The following tutorial
>(by yours truly) shows how to interface to the AD592 using RCtime:
> http://www.stampsinclass.com/downloads/em3.pdf
>
>And the following shows how to interface to photodiodes using RCtime:
> http://www.stampsinclass.com/downloads/em4.pdf
>
>Please qualify what you mean by "accurate measurement tool for sunlight
>and artificial light". In practice, photodiodes are the most useful for
>quantitative measurement, because of their range and linearity. The range
>of light from indoor to outdoor is a couple of orders of magnitude. CdS
>photocells are quite nonlinear, and thus difficult to calibrate. But CdS
>would be fine if you just need repeatablility.
>
> -- Tracy Allen
> Electronically Monitored Ecosystems
> http://www.emesystems.com
>
>
>
>
>tutorial? the AD592AN, AD592BN, or maybe one more model ( Im not sure )
>also, to answer your question, I just meant accurate to the degree of
>"dark/dusk/cloudy/sunny/really bright" not so much individual lumens.
>Anyway your tutorial is great...I ve really learned alot.
Thanks Dave!
Any of the AD592xx will work fine. The more expensive ones have tighter
specs for accuracy and linearity. But a single point calibration removes a
lot of the initial error, and calibration is a lot of what the tutorial is
about.
The CdS photocell should work fine with RCtime for what you are after. You
just need to carry it around with a portable PC and see what the reading is
at the points you define as "dark/dusk/cloudy/sunny/really bright". Good
luck!
-- Tracy Allen
Electronically Monitored Ecosystems
http://www.emesystems.com