OT: See through frosted glass!
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Posts: 46,084
Hi there everybody!
I need to make a device that can detect when a person has stepped on a 1 foot
square by 1 inch thick piece of
frosted glass, mounted flush in the floor. Essentially, when the user steps on
it, it turns on a lamp (mounted in
a 6 inch hole under the glass) and the square glows for a few seconds. All
components must be more or less
invisible to the user standing at full height, so generally they have to be a
few inches below the glass.
So far what i have tried is a cds photocell wired with a resistor as a voltage
divider. Then i measure the
voltage for changes faster than a certain rate (~1/4 second), and if the system
sees any quick luminance changes,
it lights up the lamp. Works great, but it can be triggered by things like
lights going on, shadows from outside,
etc. (That circuit was all analog- if any op amp experts want to take a look and
tell me the hundreds of things i
did wrong, that would be quite a favor...)
I also tried a Sharp gp2d02 range sensor, but that gave odd readings when
looking through frosted glass. I'm
suprised it worked at all.
any ideas?
Thanks in advance,
Raphael Abrams
I need to make a device that can detect when a person has stepped on a 1 foot
square by 1 inch thick piece of
frosted glass, mounted flush in the floor. Essentially, when the user steps on
it, it turns on a lamp (mounted in
a 6 inch hole under the glass) and the square glows for a few seconds. All
components must be more or less
invisible to the user standing at full height, so generally they have to be a
few inches below the glass.
So far what i have tried is a cds photocell wired with a resistor as a voltage
divider. Then i measure the
voltage for changes faster than a certain rate (~1/4 second), and if the system
sees any quick luminance changes,
it lights up the lamp. Works great, but it can be triggered by things like
lights going on, shadows from outside,
etc. (That circuit was all analog- if any op amp experts want to take a look and
tell me the hundreds of things i
did wrong, that would be quite a favor...)
I also tried a Sharp gp2d02 range sensor, but that gave odd readings when
looking through frosted glass. I'm
suprised it worked at all.
any ideas?
Thanks in advance,
Raphael Abrams
Comments
How about using a capacitive sensor like what you find at
www.qprox.com . That way your frosted glass floor panel could become
a "touch pad" for triggering the lamp without all of the light sensing
problems with the other methods that you have tried. The capacitive sensor
lets you turn virtually any material and thickness into a sensor. Just an
idea - see what you think.
Tim Medema
At 05:33 PM 7/11/2001 -0400, you wrote:
>Hi there everybody!
>
>I need to make a device that can detect when a person has stepped on a 1
>foot square by 1 inch thick piece of
>frosted glass, mounted flush in the floor. Essentially, when the user
>steps on it, it turns on a lamp (mounted in
>a 6 inch hole under the glass) and the square glows for a few seconds. All
>components must be more or less
>invisible to the user standing at full height, so generally they have to
>be a few inches below the glass.
>
>So far what i have tried is a cds photocell wired with a resistor as a
>voltage divider. Then i measure the
>voltage for changes faster than a certain rate (~1/4 second), and if the
>system sees any quick luminance changes,
>it lights up the lamp. Works great, but it can be triggered by things like
>lights going on, shadows from outside,
>etc. (That circuit was all analog- if any op amp experts want to take a
>look and tell me the hundreds of things i
>did wrong, that would be quite a favor...)
>I also tried a Sharp gp2d02 range sensor, but that gave odd readings when
>looking through frosted glass. I'm
>suprised it worked at all.
>
>any ideas?
>
>Thanks in advance,
>Raphael Abrams
>
>
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Timothy Medema
CrystaLite, Inc.
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232
www.crystaliteinc.com
<mailto:timm@c...>timm@c...
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[noparse][[/noparse]Non-text portions of this message have been removed]
An accelerometer chip (ADXL202 Analog Devices) glued to the glass could be
adjusted for sensitivity, to exclude lightweight objects like cats or small
dogs, but be triggered by adult humans.
Dennis
Original Message
From: raphael [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=DtqpDnfV70Me2kbp0DIKcetZsdaRdTSgXFqowJqFj6aOdzXkEx1o9zDvpcDHOHRY3fRuudx6TX0x99E]raphael@w...[/url
Sent: Wednesday, July 11, 2001 2:33 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] OT: See through frosted glass!
Hi there everybody!
I need to make a device that can detect when a person has stepped on a 1
foot square by 1 inch thick piece of
frosted glass, mounted flush in the floor. Essentially, when the user steps
on it, it turns on a lamp (mounted in
a 6 inch hole under the glass) and the square glows for a few seconds. All
components must be more or less
invisible to the user standing at full height, so generally they have to be
a few inches below the glass.
So far what i have tried is a cds photocell wired with a resistor as a
voltage divider. Then i measure the
voltage for changes faster than a certain rate (~1/4 second), and if the
system sees any quick luminance changes,
it lights up the lamp. Works great, but it can be triggered by things like
lights going on, shadows from outside,
etc. (That circuit was all analog- if any op amp experts want to take a look
and tell me the hundreds of things i
did wrong, that would be quite a favor...)
I also tried a Sharp gp2d02 range sensor, but that gave odd readings when
looking through frosted glass. I'm
suprised it worked at all.
any ideas?
Thanks in advance,
Raphael Abrams
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.
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simple and cheap!
If anybody is interested in the results, i will post them at
www.walrus.com/~raphael once i get my chips in the mail and have a few days to
try them out. It should be a couple
weeks.
thanks for the replies!
> Message: 4
> Date: Wed, 11 Jul 2001 15:14:38 -0700
> From: Timothy Medema <timm@c...>
> Subject:
>
> Hi Raphael,
>
> How about using a capacitive sensor like what you find at
> www.qprox.com . That way your frosted glass floor panel could become
> a "touch pad" for triggering the lamp without all of the light sensing
> problems with the other methods that you have tried. The capacitive sensor
> lets you turn virtually any material and thickness into a sensor. Just an
> idea - see what you think.
>
> Tim Medema
>
> At 05:33 PM 7/11/2001 -0400, you wrote:
> >Hi there everybody!
> >
> >I need to make a device that can detect when a person has stepped on a 1
> >foot square by 1 inch thick piece of
> >frosted glass, mounted flush in the floor. Essentially, when the user