photoresistor questions
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Posts: 46,084
three quick photoresistor questions:
Is the max num of photoresistors I can run off a BS2?
Would it be possible to use 24?
What is the quality of a photoresitor that makes the sensativity ( in terms of
distance)
more or less different?
Thanks --
Jordan
Is the max num of photoresistors I can run off a BS2?
Would it be possible to use 24?
What is the quality of a photoresitor that makes the sensativity ( in terms of
distance)
more or less different?
Thanks --
Jordan
Comments
Stamp only has 16 IO pins.
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: jordankanarek [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=T7JU68Kki0F6BA8xaLBY8cKRVSCPUPgPF2mGMgHTYcXnKGilak9aAUKS_ny1WrT-cabhdDnRMizXxjcgvw]jordankanarek@y...[/url
Sent: Sunday, February 22, 2004 2:35 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] photoresistor questions
three quick photoresistor questions:
Is the max num of photoresistors I can run off a BS2?
Would it be possible to use 24?
What is the quality of a photoresitor that makes the sensativity ( in
terms of distance)
more or less different?
Thanks --
Jordan
jordankanarek@y... writes:
> Is the max num of photoresistors I can run off a BS2?
A photo resistor is like any other resistor. If you wanted to use a 595 to
supply 5V you could run 64. Depends on how you are going to use them.
> Would it be possible to use 24?
>
> What is the quality of a photoresitor that makes the sensativity ( in terms
> of distance)
Distance has nothing to with a PR. It responds only to light - it doesn't
care how far away it is. All PRs contain Cadmium Sulphide. The more little
traces you can see on the top of the PR the more sensitive it is.
> more or less different?
>
Sid Weaver
W4EKQ
Port Richey, FL
[noparse][[/noparse]Non-text portions of this message have been removed]
> supply 5V you could run 64. Depends on how you are going to use them.
I am I correct in assuming that I can use RCTIME to read each of the
photoresistors
connected VIA a 595?
Which 74HC595 is reccomended for BS2?
Thanks,
Jordan
the value of your photo resistors. The '595 is a serial shift register. It can
indeed be used as a way to increase the number of Input pins to your stamp.
It will give data to the stamp as either a logic 1 or logic 0.
However, your photo resistors with the proper series resistor and voltage
applied could be intergrated for the '595 to read them IF AND ONLY IF the photo
resistor will be subjected to individual discrete amounts of light such that
the "output" of the photo resistor and series resistor combination will result
in the '595 seeing a valid logic 1 or valid logic 0 at its input terminal.
The '595 CANNOT be used to transfer the almost infinately variable value of
resistance that the photo resistor will give you based on light recieved.
If indeed your photo resistors are being used to indicate light level, you
may need to look into something like a CD4067 multiplexor combined with a serial
A to D converter.
If there is a way to read the almost infinately variable value of resistance
that the photo resistor will give you based on light recieved using a '595, I
would certainly be interested in knowing how.
I did not read the origianal post. Perhaps you can repost what the circuit is
supposed to do.
Ken
> A photo resistor is like any other resistor. If you wanted to use a 595 to
> supply 5V you could run 64. Depends on how you are going to use them.
I am I correct in assuming that I can use RCTIME to read each of the
photoresistors
connected VIA a 595?
Which 74HC595 is reccomended for BS2?
Thanks,
Jordan
[noparse][[/noparse]Non-text portions of this message have been removed]
the Allegro UCN5832, which provides 32 open collector outputs.
http://www.allegromicro.com/sf/5832/
Jordan asked about reading 24 photoresistors. The circuit idea is
that you would connect the bottom end of each photoresistor to a
separate output pin of the '5832. Connect the other end of all the
photoresistors together to one stamp pin and one integration
capacitor. The program would bring one pin on the UCN5832 low at a
time, leaving all the other pins as open circuits. Then execute the
RCtime command on the Stamp pin, which would give a result for the
selected photoresistor. Select each photoresistor in turn by
bringing its pin on the '5833 low.
-- Tracy
>I may be way off base here, but, I don't think you can use a 74hc595 to read
>the value of your photo resistors. The '595 is a serial shift register. It can
>indeed be used as a way to increase the number of Input pins to your stamp.
>It will give data to the stamp as either a logic 1 or logic 0.
>
>
>
>
>
>> A photo resistor is like any other resistor. If you wanted to use a 595 to
>> supply 5V you could run 64. Depends on how you are going to use them.
>
>I am I correct in assuming that I can use RCTIME to read each of the
>photoresistors
>connected VIA a 595?
>
>Which 74HC595 is reccomended for BS2?
>
>
>Thanks,
>Jordan
>three quick photoresistor questions:
>
>Is the max num of photoresistors I can run off a BS2?
>Would it be possible to use 24?
>
>What is the quality of a photoresitor that makes the sensativity (
>in terms of distance)
>more or less different?
>
>Thanks --
>Jordan