photo cell or light activated switch

I am curious if it would be possible to use a photo cell or some
device that would pick up an led light source and then activate a
switch to complete a ground to a circuit? Example would be some sort
of sensor mounted in your car headlamp that would pick up the light
from an LED traffic signal to activate a switch that closes a ground
circuit but has to have the capability to do this at the exact same
time every time the light comes on? Any advice would be appreciated.

 

[Rich Webb]

On Mon, 9 Mar 2009 18:28:32 -0700 (PDT), jrmotorsportz@gmail.com wrote:

I am curious if it would be possible to use a photo cell or some
device that would pick up an led light source and then activate a
switch to complete a ground to a circuit? Example would be some sort
of sensor mounted in your car headlamp that would pick up the light
from an LED traffic signal to activate a switch that closes a ground
circuit but has to have the capability to do this at the exact same
time every time the light comes on? Any advice would be appreciated.

Of course it's possible, for some specified meaning of "exact same"
(pico-, nano-, micro-, milli-second scale repeatability?).

However, for an arbitrary traffic light in an arbitrary location at an
arbitrary intersection, for a vehicle at an arbitrary location in the
line of an arbitrary mix of types and sizes of stopped vehicles, in
arbitrary weather conditions, where there's a arbitrary number and type
of potentially interfering light sources and reflections, it's a rather
challenging problem. It's certainly solvable (most drivers manage it
with some degree of success) but not trivial.

--
Rich Webb Norfolk, VA

 

On Mar 10, 8:08 am, Rich Webb <bbew...@mapson.nozirev.ten> wrote:

On Mon, 9 Mar 2009 18:28:32 -0700 (PDT), jrmotorspo...@gmail.com wrote:
I am curious if it would be possible to use a photo cell or some
device that would pick up an led light source and then activate a
switch to complete a ground to a circuit? Example would be some sort
of sensor mounted in your car headlamp that would pick up the light
from an LED traffic signal to activate a switch that closes a ground
circuit but has to have the capability to do this at the exact same
time every time the light comes on? Any advice would be appreciated.

Of course it's possible, for some specified meaning of "exact same"
(pico-, nano-, micro-, milli-second scale repeatability?).

However, for an arbitrary traffic light in an arbitrary location at an
arbitrary intersection, for a vehicle at an arbitrary location in the
line of an arbitrary mix of types and sizes of stopped vehicles, in
arbitrary weather conditions, where there's a arbitrary number and type
of potentially interfering light sources and reflections, it's a rather
challenging problem. It's certainly solvable (most drivers manage it
with some degree of success) but not trivial.

--
Rich Webb     Norfolk, VA

Exactly the same,meaning to the .0001 of a second, the same. The light
activated switch would only have one LED bulb about 30 ft. away. I was
only using traffic light an an example of the type LED bulb that the
Light activated swithch would be triggering off of. The light
activated switch would need to trigger a ground circuit at exactly (.
0001) the same time every time a LED bulb is turned on. Any ideas to
how this can be done?

 

[Rich Webb]

On Tue, 10 Mar 2009 11:51:10 -0700 (PDT), jrmotorsportz@gmail.com wrote:

Exactly the same,meaning to the .0001 of a second, the same. The light
activated switch would only have one LED bulb about 30 ft. away. I was
only using traffic light an an example of the type LED bulb that the
Light activated swithch would be triggering off of. The light
activated switch would need to trigger a ground circuit at exactly (.
0001) the same time every time a LED bulb is turned on. Any ideas to
how this can be done?

Well, a photodiode with an appropriate filter on the front end, wired to
a FET opamp set up in a transimpedance configuration would probably be a
good start. That's basically what makes up the guts of the IR receiver
section of devices with IR remote controls and they can work out to that
distance (some of them, on a good day).

--
Rich Webb Norfolk, VA

 

On Mar 10, 8:44 pm, Rich Webb <bbew...@mapson.nozirev.ten> wrote:

On Tue, 10 Mar 2009 11:51:10 -0700 (PDT), jrmotorspo...@gmail.com wrote:
Exactly the same,meaning to the .0001 of a second, the same. The light
activated switch would only have one LED bulb about 30 ft. away. I was
only using traffic light an an example of the type LED bulb that the
Light activated swithch would be triggering off of. The light
activated switch would need to trigger a ground circuit at exactly (.
0001) the same time every time a LED bulb is turned on. Any ideas to
how this can be done?

Well, a photodiode with an appropriate filter on the front end, wired to
a FET opamp set up in a transimpedance configuration would probably be a
good start. That's basically what makes up the guts of the IR receiver
section of devices with IR remote controls and they can work out to that
distance (some of them, on a good day).

--
Rich Webb     Norfolk, VA

thanks man thats at least a starting point for me to figure out how to
make this project work.