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[DPRG] FW: Any ideas?

Subject: [DPRG] FW: Any ideas?
From: RoboVac robovac at mninter.net
Date: Tue Oct 10 20:35:09 CDT 2000

The standard method for increasing the range of photoelectric sensors for
this sort of application is to pulse the beam.  To do this first measure the
amount of returned light with the light turned off.  Then measure the amount
of returned light with the light turned on.

Subtracting the two values removes the effects of room lights, sun shine,
etc.  Because of the removal of the noise from any external lights the
signal to noise ratio is higher and the sensor works at longer distances.

The same technique can be used for a laser sensor also.  However not all
laser can be pulsed in this manner.  Most of the lasers used in laser
pointers need to be left on for longer then the standard 40kHz or they do
not emit any light.

William Crolley

----- Original Message -----
>From: Robert L. Jordan <rljordan at airmail.net>
To: Dprglist at Dprg. Org (E-mail) <dprglist at dprg.org>
Cc: <fhb2000 at pacbell.net>
Sent: Sunday, October 08, 2000 10:08 PM
Subject: [DPRG] FW: Any ideas?


> Here is a good question I received. Any ideas for Hank? Sounds like he is
asking how to get more detection distance from a laser and detector at 810
nm. My thought is to use a lens in front of the detector to focus at a
distance.
> Any other suggestions or ides? Just copy the list and Hank.
>
> Thanks
> Robert L. Jordan
>
> -----Original Message-----
> From: Hank [SMTP:fhb2000 at pacbell.net]
> Sent: Sunday, October 08, 2000 3:22 PM
> To: rljordan at airmail.net
> Subject: Any ideas?
>
> Do you or someone you know have any optoelectronics ideas?  It's a a
silicon detector problem.  I'm utilizing the BS2SX and a 5mw laser diode
module @ 810nm and a silicon detector with a 810nm narrow bandwidth filter
to measure when this IR laser pointer strikes black or white.  Laser and
detector are side by side and measure light reflected back.  I know it's
possible or those long range bar code scanners wouldn't work.  Only need
object detection not bar codes.
> I can only detect out 2-3ft, but need 8ft range.  I don't understand the
> capacitance or resistance to make detector more sensitive.
> I think my op amp is maxing out too.
> Thanks - hope you can help,
> Hank Burbeck
>
>
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