View Full Version : photocells

05-03-2006, 01:21 AM
Thank you for your help with my question about photocells. I had several
requests for a summary of responses. Hope this helps.

Darla Smith

I have recently purchased a Brower Timing System for a similar purpose.

It is completely wireless (although they offer a wired version) and is
extremely portable and easy to set up. Please let me know if you need
any additional information.

Here is the link for reference:



Karen J. Nolan

Try www.bannerengineering.com
. They have lots of different
photocells - most for $100-$150. They work quite well. The engineers
there are very helpful and can tell you which one would best fit your

Good luck,

Scott McLean, Ph.D.

A few years ago we got some very serviceable beam detectors from Radio
Shack which were designed for security purposes but which we used to
detect arm swings in standing subjects. The units come as a pair (one
light source and one detector) and I think they can be wired either
normally open or normally closed.

Professor Larry Abraham

Be sure to check these vendors:



Depending upon your budget, how much time you want to set up the lights,
accuracy, etc., they may suit your application.

Gary Scheirman

Vicon Peak

Sircon Controls (http://www.sirconcontrols.com/) sells
photocells/reflectors for $152 a piece. We use them for velocity
measurement across a force plateform and they work fine.
Tanya Garcia-Nolen

I forgot to mention, these photocells only provide a TTL or switch
signal, you would have to have additional hardware or software to
calculate and display timing information. We use Lafayette Instruments
Economy Clock Counter ($295) to measure time between 2 photocells and
knowing their distance apart calculate velocity.

A few years ago, I bought some cheap ones at Radio Shack that have
worked well for a similar purpose for me. I think they were marketed as
part of a home security system... don't know if they still sell them.

Best regards,

Gregory M. Karst, PT, PhD

In our lab we used infra-red ports.
Two * one infra-red light and a reflector connected to a digital clock.
Passing through the first infra-red line starts the digital timer.
Passing through the second stps the digital clock.
If the infra-red lights are placed upon 3.3 meter and a person passes
through in 1 second, he/she will run at 3.3m/s or 12 km/h.
I maid a simple drawing

(I had to remove Veerle's drawing, because of the listserv rules - drs)

The only disadvantage is that a constant speed is not necessary.
So in the second experiment we placed not 2 but three infra-red

This could be a cheap safe option, I think

Kind greetings
veerl segers

I'm not sure if this would suit your project, but I have used in the
past a cheap Radio Shack infrared beam. This is the kind they put at
the front door and it rings when you walk through the door. They put
out a 12 volt pulse, so you can then input it into your computer or
whatever. I had the beam go across to one mirror at 45 degrees,
followed by another one at 45 degrees, then the reflector...then the
beam bounced back. This is a little tougher as the mirrors have to be
perfectly aligned due to the return trip of the beam. It would be
easier if you used two of them.