What is the best type of light gate that will sense a small vehicle going through it straight away. And also best for long transmittal?

any ideas would be cool

Like this guy

 

IR transmitter, IR receiver, long cable.

 

Someone holding a flashlight in the middle of the road. It the flashlight is off, then you know that the person was ran over by a car. You could ask that person to use a radio transceiver or a cell-phone, to solve the long distance problem as well.

Now seriously, what do you have in mind?

 

Just so that you know, you must not use a laser device. It is illegal to point one at a motor vehicle or aircraft in many countries.

It is also dangerous, because you may distract the driver and cause an accident.

 

Even an IR beam?

 

Can run into problems with infra-red. I tried making a gateway alert system for my mother but I was unable to adequately shield the sensor from sunlight so would get the ding-dong alert every morning - until the plug was finally pulled on the whole scheme... Used to get false alarms from condensation as well as small animals climbing up the post the sensor was embedded in.

 

What distances were between the Beams, which worked best?

 

The sunlight issue could be beat several ways, a simple AC tone riding on the beam would eliminate other sources of light, as well as allowing simple amplification on the reciever (AC is easier to reliably amplify than DC in many cases).

The other is a tube, painted flat black on the inside, to absorb ambient light before it hits the detector.

Lasers aren't that necessary. Modern LEDs are plenty bright and collimated enough do the job.

A simple 555 circuit could make the LED pulse. It could also have an added benefit of reducing the power used by the LED.

The receiver wold be a little more complex. How you communicate it back to the house would be a bit of a challenge. Have you thought how you would power these gadgets?

 

You can get PIN photo diodes with filter for visible light. As an example the SFH 2030F.

 

use of IR encoder/decoder ic's such as ones by Holtek, could also solve communication errors, and false triggering, if the IR beam is modulated at around 38khz, then the receiver can look for only that modulated signal..... like tv remotes.....

for the home receiver unit I would use RF transmitters / Receivers like the ones manufactured by Linx Technologies (http://www.linxtechnologies.com/Products/RF-Modules/)....

my .02

 

Would the "RF transmitters / Receivers like the ones manufactured by Linx Technologies" be too much for the project, and would it help the project or hinder it slightly?

 

Would the "RF transmitters / Receivers like the ones manufactured by Linx Technologies" be too much for the project, and would it help the project or hinder it slightly?

These modules are very low cost and do not require hardly any external components, for under $20.00 dollars you can get a matching transmitter receiver modules and the 1/4 whip antennas they need at DigiKey....

or you can go to Rentron.com and purchase premade modules..... http://www.rentron.com/remote_control/TXLC-XXX-LR.htm

 

For the sun problem, point the detector away from the sun at local noon, and add a black tube in front, as has been mentioned. As to climbing critters, use two transceiver pairs, separated by a distance greater than the length of the critter. You'll need to do some research, and decide if the distance needs to be that of the "average" critter, or that of "the largest" critter of this type. Don't trip the alarm unless both detectors are active.

--Rich

 

I have posted a new thread to try to accomplish about the same thing, but the distance factor comes into accont for IR (I need the light beam to cross an arena about 125 ft in direct sunlight) I choose a green laser (not illegal to point at horses) shooting a cadmium sulfide photocell (Radio Shack pt no 276 1657) for a emmitter/detector. But I woulf like a schematic to make the photo cell close a simple ground switch when the beam is broken. Any Ideas?

 

I have posted a new thread to try to accomplish about the same thing, but the distance factor comes into accont for IR (I need the light beam to cross an arena about 125 ft in direct sunlight) I choose a green laser (not illegal to point at horses) shooting a cadmium sulfide photocell (Radio Shack pt no 276 1657) for a emmitter/detector. But I woulf like a schematic to make the photo cell close a simple ground switch when the beam is broken. Any Ideas?

use a NPN (2N3904) type transistor on the output of the photocell to switch a load to ground......

 

Thanks to everyone for here input, I will attempt to help you all as much as you have helped me.