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[DPRG] FW: Any ideas?

Subject: [DPRG] FW: Any ideas?
From: RoboVac robovac at mninter.net
Date: Wed Oct 11 23:59:00 CDT 2000

The technical name for a high speed shutter to convert a constant light
source to a pulsed light source is a chopper.  Typically they are a motor
turning a disk with holes or slots in it.  An added complication to using
them is getting the mechanical motion synchronized with the electrical
reading of the amount of light.  Adding an encoder solves that, but the
whole project starts getting a lot more complicated then it first seems.

William Crolley

----- Original Message -----
>From: Ralph Tenny <rten at metronet.com>
To: RoboVac <robovac at mninter.net>
Cc: Robert L. Jordan <rljordan at airmail.net>; Dprglist at Dprg. Org (E-mail)
<dprglist at dprg.org>; <fhb2000 at pacbell.net>
Sent: Wednesday, October 11, 2000 2:45 PM
Subject: Re: [DPRG] FW: Any ideas?


> Just a thought -- could a laser pointer be "pulsed" with a high speed
> shutter or other method to interrupt the beam?
> Ralph
>
> On Tue, 10 Oct 2000, RoboVac wrote:
>
> >
> > 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
> > >
> > >
> > > _______________________________________________
> > > DPRGlist mailing list
> > > DPRGlist at dprg.org
> > > http://nimon.ncc.com/mailman/listinfo/dprglist
>
>
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