Cheap train detection for hidden staging. Ya'll critique my plan.

[Anonymous]

QUOTE: A magnet and a few switches more complicated than a closed circuit TV system? When did that happen?

I am somewhat of an old fart so I chuckled too. I do know that it all happened long enough ago for there to be lots of cheap cheap deals on old stuff.

One swap meet deal got me a bunch of surveillance cameras; 3 low lux BW lens on PCB cams, 1 1/4 lux and IR sensitive BW lens on PCB cam and 2 high res BW PCB with lens adapter for 16mm movie camera lens ..$25 the lot.

Another deal was 2 full size Panasonic camcorders for $20. good video on both but only one records.

I also have a Minolta and a couple of Sony handycams. Good cam No corder.

BW or Monochrome monitors are free for the taking. I already had a few. My total cost for 11 camera setup including Radio shack switch boxes is still below $100 CANADIAN!

[grandeman]

QUOTE: Originally posted by SteelMonsters

This might be a cheap option if you want a bunch more for whatever reason.

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=171871

Thanks for the great link!

[SteelMonsters]

This might be a cheap option if you want a bunch more for whatever reason.

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=171871

[grandeman]

Hi all. Here's an update on tonight's progress.

Loaded West Yard. From the water heater until they appear on the layout, trains only travel approx 6 feet.


Installed reed switches. These are for the west yard's red LED's, but the green LED switches were installed tonight as well.


Continuity!!! The test loco tripped all eight switches with no problems. It's hard to see from the pic, but the meter reads one ohm.


The west yard detection is coming along nicely. I need to run the ground side wire to the yard and mount the indication panel. One of the panel's red LED's still has to be installed. Hopefully we'll test the system soon!


One last update and I'll let this dog lie. Today I finished the South yard, installed the indication panel, and wired the detection to the panel. So far, the system is working better than I'd hoped!!! I think we're really going to be happy with it.

ETA, the system is complete. Here's a shot of the indication panel during our first test ops session!

[grandeman]

Hey guys. Thanks for the input. I think CC TV is great but we'll have three yards to monitor and the North yard will be a minimal distance above the South yard. I'm thinking TV could be difficult to do.

[roadrat]

I have to agree with "scubaterry & markpierce" the closed circ TV system is easy and fool proof (well sort of) if you can see the track then you know if there is a train there.
you can even shave off a few extra $$ by buying an older B/W camera.

just my [2c]

bill

[scubaterry]

Grande man - I agree with markpierce! I plan on putting in a micro camera on my hidden stage area hooked up to a cheap 12 inch TV. As a matter of fact I may put several cameras around the layout just for the heck of it to keep track of things so I don't have to get off my butt. But seriously I have seen the micro cameras going for 60 bucks lately. You don't need the sound version, more money saved. You could pick up a used 12 in(or so) TV at a flea market or yard sale. You can buy brand new ones for less than 70 bucks. Probably more than you wanted to spend but far simpler and bullet proof (??)
Terry

[grandeman]

QUOTE: Originally posted by Student of Big Sky Blue

One thing I have thought of, Potentially you might want to put some yellow indicaters along the legth of track diagram so you could track progress of the train down the track? I am many years away from having to worry about staging. But that just seems something that should be done incase there is a break down or some kind.

James

That's a good idea that may come to pass. We'll wait and see how the original plan works and add extra LEDs if needed.

Now for an update. I am going to use a separate power supply. It'll be a 12v unit rated for 1 amp (since that's what I found in my "junk" box [:D]) . The wiring will be a common power lead bussed thru board mounted resistors to the LEDs. The reed switches will complete the ground side of the circuit for each staging track. Here's a pic of tonight's progress. The terminal strips on the sides will be connections from the 4 conductor phone wires (6 total) going out to the reed switches (each yard will have a ground line from the power supply). The black wire in the center of the pic (verticle) is the Positive lead that will be connected directly to the power supply. The other is a buss wire between the resistors. The resistors are soldered together on the power side to buss them together


Comments, questions or heckling from the peanut gallery??? [:D] You guys pick the new plan apart for problems I haven't thought of.

[Anonymous]

One thing I have thought of, Potentially you might want to put some yellow indicaters along the legth of track diagram so you could track progress of the train down the track? I am many years away from having to worry about staging. But that just seems something that should be done incase there is a break down or some kind.

James

[grandeman]

QUOTE: Originally posted by mark_in_utah

QUOTE: Originally posted by grande man

The thought strikes me that if a separate power supply were used, it could have a low voltage and eliminate the resistor board altogether...

NOT!

An LED is a current device, and not a voltage device. An LED won't conduct current until the bias voltage exceeds the minimum, and then it conducts current ike crazy. The resistor is to limit that current flow.


If your power supply was a Thevenin current source set to 20 mA then you'd be in good shape.....

Mark in Utah

Thanks Mark! I love electronics...[:D]

[Anonymous]

QUOTE: Originally posted by grande man

The thought strikes me that if a separate power supply were used, it could have a low voltage and eliminate the resistor board altogether...

NOT!

An LED is a current device, and not a voltage device. An LED won't conduct current until the bias voltage exceeds the minimum, and then it conducts current ike crazy. The resistor is to limit that current flow.

If your power supply was a Thevenin current source set to 20 mA then you'd be in good shape.....

Mark in Utah

[grandeman]

Space, it looks like I'm gonna be your guinea pig. I'll let you know how this works before you spend any $$$. [8D]

[grandeman]

QUOTE: Originally posted by jdtoronto

All of the various suggestions here will work, but none really any better than any other. I am an electronics engineer, so lets look at the various suggestions that have been made here and elsewhere.

Magnets and reeds - Despite comments to the contrary, reed switches are quite reliable, if they are of good quality and tested before use.

John, thanks for the valuable info. I had previously heard that mag reed switches were reliable in low current applications.

As for price, I bought enough reed switches, LEDs/resistors, and magnets for about $60. I'm sure Miniatronics isn't the cheapest stuff out there, but their quality is isn't in question.

How do you feel about powering the system off track power? It makes since to me since we use LEDs for loco lighting off track power all the time. It would reduce the amount of wiring. Still, the arguments against it make since as well.

[Anonymous]

All of the various suggestions here will work, but none really any better than any other. I am an electronics engineer, so lets look at the various suggestions that have been made here and elsewhere.

Magnets and reeds - Despite comments to the contrary, reed switches are quite reliable, if they are of good quality and tested before use. They are hermetically sealed so do not suffer from corrosion. Choice of contact materials can be significant, especially at low currents, but as theya re here proposed to drive LED's that is not an issue. Magents are an issue, polar orientation could be an issue with magnetic uncouplers, but I suspect not. Spacing can be an issue and I would suggest that you could look on eBay for some Neodymium or other intense field rare-earth magnets. Small magnet - strong field - keeps the reed switch further from the rolling stock for safer clearances.

Cross track optical - great for a hidden staging of course, but has lots of visible stuff. Beware of the effects of incandescent room lighting or incandescent lights in locos etc. The sensor should have an IR filter in the optical path. Very reliable, low cost.

Vertical optical - about 10 years ago I designed a train detection system for a hidden staging for a friend which used IR, the roof of the staging area was solid, so we mounted tiny reflectors above each sensor point. This kept al the electronics in one place and is still working today. The detection circuitry is a little more complex, but after the initial cost of making PCB's it is still relatively inexpensive.

Magnetic proximity detection - common in many industrial applications - you have a magnetic field which is disturbed by the movement of the target object, fine if you have lots of magnetic material such as steel in the object. Great for garden railways but despite efforts by some it is really unsiotable for use on small scale layouts - too much plastic and aluminium.

RF Field proximity detection - create a sinmple RF oscillator where the field of the resonant circuit encompasses the sapce where the loco will pass. As pretty much anything goes thourhg the earea the frewuerncy will change and detecting this will trigger whatever is behind it. Complex and offers no real advantage but was a cheap alternative in the 50's and 60's before modern semiconductors.

SPACEMOUSE: Your suggestion of using photo-voltaic detectors (for the others: photo voltaic detectorsa generate a small amount of electric current in response to light - basically like the solar cells you see on roofs etc). Good idea if you can find a sensor with sufficient output to be usable at a reasonable price. But I am not sure that you can get enough form them to be usable at light levels that would be unobtrusive. But it is certianly an interesting thought and if you pursue it further I would love to hear the rsults of your experiments.

Rob Paisley has a simple and elegant 8 channel optical detector board available, you can buy just the bare PCB form him. It can use photo-transistors or CdS (Cadmium Selenide) cells. http://home.cogeco.ca/~rpaisley4/8PhotoDetect.html

John

[SpaceMouse]

Since I'm about a month behind G-man here, I wouldn't mind seeing a link to an example or two of IR circuits. I was thinking photo-voltaic, but I can be corrupted.

[cacole]

Using reed switches and magnets seems to me to be a much more expensive and unreliable system than current detection or IR detectors. If I were designing this, I think I would prefer IR and would try to avoid current detection, too, because now you have the added expense of resistor wheel sets to consider.

If you want to continue with reed switches and magnets, a good source to consider is http://www.allelectronics.com

[rrinker]

Interesting - probably because of the way the Kadee magnets are polarized, down the long axis - so along the strip of magnet you only have half attracting and half repelling, which should balance out.

--Randy

[grandeman]

Randy, the Kadee magnets don't seem to present any special problems. The magnet equipped loco just glides right over them. Interesting that the benchwork screw seems to have more effect.

[ndbprr]

very interesting idea. I think Infrared may be easier to provide constant light that there is occupation, but then again you will get flicker between cars.

No you have the wrong conception. I am placing a beam of light like an electronic eye accross the tracks at a 90 degree angle. Anything on any track that breaks the beam will light the light so you bring a train into the staging yard until the light goes on or off and then back up a little to reset it. there would be no flicker.

[railroadyoshi]

very interesting idea. I think Infrared may be easier to provide constant light that there is occupation, but then again you will get flicker between cars. I had the same issue as spacemouse, but you seems to have found no problem with that. Hope you find a way around the uncoupling magnets.
Best of luck, and would like to see the results[tup]

[Anonymous]

QUOTE: Originally posted by markpierce

Not being electronically inclined, this is all too complicated to me. I think a simpler and cheaper method is to use a camera(s) connected to a closed circuit TV.

I am up to date on technology enough th agree with this 100% but I am old enough that it struck me as funny when I first read it. A magnet and a few switches more complicated than a closed circuit TV system? When did that happen?

[ndbprr]

I plan to use a pair of infrared transistors. one is the emitter and the other is the receiver. When the receiver senses the source infrared it closes and can light an LED or bulb. the advantage is placing the two say an inch from the end of the tracks so when a train breaks the circuit the light goes out (or on with a hex inverter). That way it only takes the two transistors for all the tracks if you then back the offending trains back a little and stop breaking the plane of the light. I intend to use a small brass tube on the emitter to help focus the light better. I tried reed switches once and wasn't happy with them but it could have been me.

[rrinker]

If this is a hidden staging area - a simple IR beam-breaker type of thing would work just fine too, and require no alteration to the rolling stock. There are a bunch of suitable circuits on Rob Paisley's site, and there are commercial items such as the IRDOT.

--Randy

[grandeman]

QUOTE: Originally posted by rrinker

Shouldn't be a problem with the motor. Trying to pass over top kadee uncoupling magnets, on the other hand....

--Randy

YIKES! I hadn't thought of that! I'll check it out tonight.

[cwclark]

the problem is going to be getting the magnet on the locomotive and the reed switch perfectly lined for it to work....another drawback is that reed switches don'y always work like they should...it's a mechanical device and they are prone to hang up at the contact hinge... it may be better to just bite the bullet. spend the money and purchase the train detection circuits...then all you have to install is the TDC, a trickle voltage power source, and some resistors on your rolling stock wheels to set off the occupied block LED....chuck

[rrinker]

Shouldn't be a problem with the motor. Trying to pass over top kadee uncoupling magnets, on the other hand....

--Randy

[Anonymous]

I was wondering about the magnet under the motor, too, but since it looked like he was already running that way I figured it must be working. The screw slowing the train down is interesting...

[markpierce]

Not being electronically inclined, this is all too complicated to me. I think a simpler and cheaper method is to use a camera(s) connected to a closed circuit TV.

[joeyegarner]

Hey everyone here is a link on ebay for reed switches. http://cgi.ebay.com/Latching-Reed-Switch_W0QQitemZ6007419775QQcategoryZ19127QQtcZphotoQQcmdZViewItem