IR detector progress


T

TomR

Member
I just finished the PC layout for my IR detector system, and ordered boards. I can reliably detect a single car or more within a span up to five feet.

Now I have to figure out how to hid the LED's and IR photo transistors. I'm thinking of making or buying some fake track side boxes of various types.

Are there any small trackside things I might hide the LED's and detector's in?? They are common LED bulb sized. About 1/4 inch diamter and about .35 inches long.

Something like hot box detectors, or radio / signal system cabinets?

Tom
 
Maybe try a fault detector setup. They've got sensors to check for bad bearings, dragging equipment, loads of stuff. No doubt there's something there that'll hide an LED. :)
 
How about tie piles, rail stands, tufts of weeds, pallets with otm.
Depending on how close you need them to the rails they could be in old vehicles, lineside shacks, tree tunks, cars at crossings...
 
I was thinking along the same lines as Rico, line side weeds or bushes.. Cabinets are usually in specific locations whereas weeds and bushes are more random..

I suppose it really depends on the sceniced location(s) your looking at situating them at!?! Town/Country etc..
 
Do you have a hard time aligning them, I want to install some on hiddien track with just a simple circut with an indicator light showing condition.
 
Hey Tom,

In some early experimenting, I made a bunch of these "dwarf signals". They're massively oversize, but don't actually look to bad mounted down low. [They're bicolor 5mm LEDS btw.]

Cheers,
Ian
 
fast_ian said:
Hey Tom,

In some early experimenting, I made a bunch of these "dwarf signals". They're massively oversize, but don't actually look to bad mounted down low. [They're bicolor 5mm LEDS btw.]

Cheers,
Ian
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That looks good.

I'd like to hide them in grass, but the lamps need to be at coupling height or slightly greater. I was thinking of little boxes like signal control boxes or communication equipment sheds, rocks, dwarf signals, or even mount a little box to hide the bulb on the existing poles near tracks.

Do you have a hard time aligning them, I want to install some on hiddien track with just a simple circut with an indicator light showing condition.
Click to expand...

I put a little red LED to indicate lack of signal on the board. The detector boards are two channels so they will have two sensitivity pots with indicator LED's next to them. The most critical alignment is the detectors I use, because they have narrow beamwidth. They definitely have to be properly aimed.

The IR source LED's are wide enough, at a few feet, to cover a couple inches of beamwidth.

I'm excited about this, because it opens the door to all sorts of neat effects. Like automatic train control. This is all for my grandkids of course, not for me.

Tom
 
Rico said:
I've been toying with the idea of using one of these:http://www.glade.com/en-US/Products/Pages/GladeSenseSprayAutomaticFreshener.aspx
for one of my hidden junctions.
It works by motion detection and activates a small motor with a cam that presses down on an aerosol canister.
Who says it couldn't activate a signal arm or LED?
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Maybe it could. Maybe not though.

Most detctors like that work on heat, like a motion detector normally does. It might sense the light from a headlamp moving across the detection space, or it might not. You'd have to try one.

I settled on an IR beam that is narrow and runs down the track, and anything on the track breaks the beam and triggers the detector.

A board with eight detectors and eight track control relays looks like this:

IR%20and%20relay.gif


The detectors are pretty small, about 1/4 inch diameter by maybe 3/8th inch long.

Tom
 
Are you using modulated light, or are these things just shining with constant (invisible) brightness all the time? If it's not modulated, you must be at a lot of risk that ambient light will hit the sensors and make it seem as if the track is never occupied. If your sensors can see daylight, for instance, I'd be skeptical that they'll ever work. But if you use 38KHz modulation and TV remote sensors, that would sound right. In fact 5ft is pretty small compared with what they're capable of.
 
John P said:
Are you using modulated light, or are these things just shining with constant (invisible) brightness all the time? If it's not modulated, you must be at a lot of risk that ambient light will hit the sensors and make it seem as if the track is never occupied. If your sensors can see daylight, for instance, I'd be skeptical that they'll ever work. But if you use 38KHz modulation and TV remote sensors, that would sound right. In fact 5ft is pretty small compared with what they're capable of.
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I considered a modulated IR source and active detector filter for that frequency, along with automatic bias control on the detector to always keep it out of saturation. I built a prototype using a 2 kHz source and 2 kHz filter, and could detect about 15 feet away in normal bright room light.....but at that distance the beamwidth made it useless anyway.

I found it wasn't necessary at all to use a special source and filtered decoder with the IR source I picked and the narrow beamwidth detector. Even with the garage door wide open and sunlight there is no problem at all over the useful distances for detecting a single track width area.

It's 100% reliable at the maximum distance that covers a single track width (my tracks are mostly 2.5 inch spacing on centers), unless the narrow beamwidth detector is aimed right into a bright source, which just doesn't happen because they are aimed parallel to the track and about 1/2 inch or so above the rails.

Tom
 
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