infared sensor

I use them for signals, I bought them on eBay.  I also have some Lionel 153IR sensors.

 

I have the Ebay stuff. comes from China via Alabama. very reasonable.

they work

 

Ralph

Stan, where are you getting modulated IR circuits for a few bucks?

Published DIY occupancy detector circuits use the 555 timer to modulate an IR LED.  The frequency tolerance of IR receivers is wide enough to handle the expected resistor-capacitor variations.  A 555 oscillator would be about $1.  I have not used this approach but take it at face value.

 

For about $1.50 (DigiKey pricing), I found this circuit I made 25 years ago that uses a 4 MHz transistor crystal oscillator driving a divide-by-100 digital IC (74HC390) so the output is 40.0 kHz exactly.  This is a common IR receiver modulation frequency.  More assembly effort than a 555 circuit but more stable.

 

 

If doing it today (2014), I would probably use a microcontroller chip such as a PIC with a built-in 1% stable oscillator.  This would be the most compact implementation, would not need any external oscillator components, and would be maybe 50 cents.  Or if this were part of a system with timers to control crossing gates, signals, etc., I'd go with an Arduino or the like which could generate the transmitter modulation.  Of course these approaches require programming which is not suited to everyone's interests.

 

In any case, any of these approaches would drive an IR LED - about 25 cents. The IR LEDs for an activation/occupancy circuit probably need only a few mA of current since the distances involved are only inches.  Thus, one oscillator circuit can drive/modulate multiple IR LEDs.  So if you need several transmitter-receiver pairs, this can save some cost/assembly effort on the transmitter side if it's practical to run wiring between set-ups.

 

Kinda' what I thought, all of these approaches are probably out of reach for 99% of the folks here.

This looks pretty simple to me.

Although when no IR is detected, output is high.

When IR is detected, output is low.

 

I was talking about the modulated model, not the simple IR detection.

 

 

Here's a cheap solution that I'm using, and it's worked quite well.  I have both sensor and emitter in a post next to the track and when it's reflected off a passing train, I trigger the signal.  I have had no issues with false triggers.

 

C:US:3160" target="_blank">Logic Delay Switch Circuit Boards

 

 

Here is what I use on my layout. See link for more details on use.

http://www.tuveson.com/Detector/Detector.htm 

 

Show here using a relay out but I drive my signal logic and grade crossing flashers directly from the 556.

 

Here are the IR pair that are used in the track to detect trains.

 

 

Carl

 

 

 

Gunner

i use the same. Very good for the price

Unless circuit boards were available, I'll stick to the canned solution above.  

 

The unit I posted comes with both IR emitter and detector, as well as a reed switch and magnet for an alternative detection method.  It also has an adjustable delay, runs from AC or DC, and will control 3-aspect signals as well as 2-aspect signals.

 

I have been using Azatrax IR sensors with good results. They have several models, and their customer support is excellent as well.

 

Alex

I have used virtually every type of electronic/electrical train detection system in my layout and almost all worked just as they were intended. I even wrote an article on this subject a few years ago. I do like IR detection but if you want flawless performance, I would go with the emitter and detector on opposite sides of the track and angled about 30 degrees from perpendicular so that spaces between cars won't matter.

Agree 100%. The Azatrax sensors, to which I referred above, can be placed up to 18 inches apart, so they can be across two or three tracks, and at an angle. In addition they have selectable delays so the crossing signals can stay on for half or for three seconds after the train has cleared the crossing, for instance. The delay is intended also so that if there any gaps along the train, the signal will not be dropped too soon.

 

Alex

 

 

I had a picture, but I can't find it now.  I built a little hollow enclosure about 1/2" square with a peaked top.  The emitter and sensor are mounted in that about 1/2" apart vertically.  I put numbers on it to make it look like it belongs there.  This is on our modular club modules.  I made mine out of wood, and just routed a channel into the piece, then glued a thin piece on to cover the channel after mounting the LED and sensor.  I painted the whole thing silver.

 

Gun: I assume the little circuit board is mounted under the train platform. I do not see any mounting holes on the pictured circuit board. What did you use to mount the board?

 

I would love to see a photo of your "makeshift" enclosures for the IR emitter and receiver. 

I use sticky-back Velcro to mount it under the platform.

I was thinking about this green is normally on. train trips it  it goes red couldn't you wire up the previous signal's yellow to the red input that way as long as it is red the yellow would stay on. would that work. that way it doesn't turn green before the train moves off the block

 

gunrunnerjohn: I bought the same sytem you have last night I spent literly 3 hrs trying to get the IR sensor to trigger correctly via fastrack  did you mount it in the track pointing up at the bottom of the train or across the tracks.

 

I forgot to get a picture of it on my module.  I have the LED and sensor mounted about 1/2" apart inside a small mile marker post on the side of the track, the train comes by at about 1/2" away.  It triggers pretty faithfully so far.  I haven't tried to mount it facing up, I figured the florescent lights above it would probably be tripping it.

 

I was trying to shoot it across the track about 5 inchs apart not working very well so you mounted tehn on the same side next to each other

 

Yep, I couldn't get them to trigger reliably that far apart either. The two mounted on the same side work much better.  I can't say that they trigger on the very first part of the locomotive, but a steamer or diesel with no cars triggers it every time.

 

I bought some bare IR emitters and receivers, I may tinker with the PIC processor and make a modulated one that will have a lot more light immunity.  If you modulate it, you can then just detect only that frequency, makes for a much more reliable trigger.

 

Are they tripping too easy or skipping? More than likely Im preaching to the choir, but here goes...Checking into the focus, brightness, and AIM of LEDs can help to correct E/R issues too. Not all LEDs are equal, even brand variances can improve or wreck the performance. Using your digital camera or phone, and a dark room, you can likely see IR from LEDs. You wont see a "beam", but the receiver should look noticeably brighter when the IR is aimed right and shining on it. For under track mounting, a silver or white sticker/paint, or shiny bare metal spot on the stock will help reflect the light more consistently. Often the paired E/R wheel readers are cheaper, and the plastic housings can be cut in half with a hack saw blade to separate the two components, each still screw mountable by the remaining tab (available on some).

 My experience is from repair/ maintenance of coin-op vending/gaming where they had to detect everything from the vector of moving coins mid-air, to the notches and holes in the tickets the games puked out. Did my share of fiddling, but designing the actual circuits not my really thing, good luck.    

they were not Tripping moved one to the other side next to each other about half inch apart works now.there inside the little box

It that the box behind the signal?  I actually have mine closer to the track, but if it works there, that's all that counts, right?