Simple Block Detection w/Signal

[robertjohndavis]

Hi - I am looking for a very simple DCC-compatible block detection system that can switch a lineside signal between red and green. Just one block.  No other tricks required. If something in the block draws current, the signal is red. Otherwise it is green.

I am sure there are 1000 ways to build such a beast, but I am looking for an off the shelf solution that I can hook up to the track and to a signal. Electronics aren’t my thing, so simple is better.

Anyone have a recco for a simple set up like this?

Thanks much!

Rob

[tehachapifan]

Are you locked into the current detection idea? The reason I ask is there are really simple photo cell based options available as well.

[robertjohndavis]

Good question. I am open to anything that provides true detection. What I want to avoid is an IR solution that triggers a times response from the signal. I need the signal to accurately reflect occupancy at all times- Rob

[Rasputen]

One solution would be to find an older Digitrax BD1 single block detector or a BD4.  These can be used as a stand-alone device as long as they are grounded to the booster.  The only problem I see is that the output can turn an LED on and off, not switch between two different colors. Note that some people have reported problems with compatibility between high frequency BEMF decoders and BD1s/BD4s. 

[ednadolski]

If something in the block draws current, the signal is red. Otherwise it is green.

If 'something' in this context includes freight cars, remember then you'll have to install resistor wheelsets on whatever cars you want it to be able to detect in the block.

Ed

[C855B]

Good question. I am open to anything that provides true detection. What I want to avoid is an IR solution that triggers a times response from the signal. I need the signal to accurately reflect occupancy at all times- Rob

There are a few off-the-shelf detectors - a/k/a "Chubb Detectors" - designed for DCC that will yield a +5V voltage on occupancy, 0V on not occupied. It would be up to you to put a low-current relay on it to switch between red and green.

The detector I use: http://www.modelrailroadcontrolsystems.com/cpod-control-point-occupancy-detector/
A suitable relay: https://www.ebay.com/itm/1-Channel-DC-5V-Relay-Switch-Board-Module-for-Arduino-Raspberry-Pi-PIC-ARM/221959450343

Don't forget Ed's comment about resistor wheelsets, otherwise it will detect only locos and lighted passenger cars.

[robertjohndavis]

If 'something' in this context includes freight cars, remember then you'll have to install resistor wheelsets on whatever cars you want it to be able to detect in the block.

Ed

I am prepared to take the resistor wheelset step, but I appreciate the reminder Ed. It’s all for naught if there’s no current draw.

[robertjohndavis]

There are a few off-the-shelf detectors - a/k/a "Chubb Detectors" - designed for DCC that will yield a +5V voltage on occupancy, 0V on not occupied. It would be up to you to put a low-current relay on it to switch between red and green.

The detector I use: http://www.modelrailroadcontrolsystems.com/cpod-control-point-occupancy-detector/
A suitable relay: https://www.ebay.com/itm/1-Channel-DC-5V-Relay-Switch-Board-Module-for-Arduino-Raspberry-Pi-PIC-ARM/221959450343

Don't forget Ed's comment about resistor wheelsets, otherwise it will detect only locos and lighted passenger cars.

Thank you, Mike. Will check out those options.

[porkypine52]

I'm going to use a simple light sensing switch for some hidden track in a off layout storage yard.  You have a small light source over a light sensitive switch.  The switch can go ON or OFF, depending on type. when the light hits it.  Engine or rolling stock will block light source.  Turn off or on a light on the control panel.  Very simple, no need to have to change car axles.  Check[Google] around for some Model Railroad Electrical Websites. There are some good ones out there.  Just depends on technical or fancy you want to go. 

    DIESELS ?!?!?! We Don't Need NO Stinkin' DIESELS!!!

    THE INDIANA RAILWAY--100% STEAM POWERED in 2020

    MARK


    Suppose you were an idiot. And suppose you were a member of Congress. But I repeat myself.
    - Mark Twain, 

[John]

If you want to build it

http://www.circuitous.ca/DccBODvt5.html

[ednadolski]

If you want to build it

http://www.circuitous.ca/DccBODvt5.html

If building is an option, you can make something simpler from a few discrete components like this:

Basic circuit:
http://www.trainelectronics.com/DCC_Arduino/Current_Sense/images_current_sense/schematic.gif

With four detectors on one board:


Circuits in operation:

Thread:
https://www.therailwire.net/forum/index.php?topic=37285.msg482465#msg482465

[robertjohndavis]

I'm going to use a simple light sensing switch for some hidden track in a off layout storage yard.  You have a small light source over a light sensitive switch.  The switch can go ON or OFF, depending on type. when the light hits it.  Engine or rolling stock will block light source.  Turn off or on a light on the control panel.  Very simple, no need to have to change car axles.  Check[Google] around for some Model Railroad Electrical Websites. There are some good ones out there.  Just depends on technical or fancy you want to go. 

The reason I am shying away from (not not totally discounting) a light-source solution is a) if the train is in the block but not covering the sensor, the signal shows clear and b) to fix that with two sensors (in/out one at each end of the block) seems like more work than simple occupancy detection.

Rob

[robertjohndavis]

If building is an option, you can make something simpler from a few discrete components like this:

Basic circuit:
http://www.trainelectronics.com/DCC_Arduino/Current_Sense/images_current_sense/schematic.gif

With four detectors on one board:


Circuits in operation:

Thread:
https://www.therailwire.net/forum/index.php?topic=37285.msg482465#msg482465

That's slick and with a defect detector! Cool!

[John]

If building is an option, you can make something simpler from a few discrete components like this:

Basic circuit:
http://www.trainelectronics.com/DCC_Arduino/Current_Sense/images_current_sense/schematic.gif

With four detectors on one board:


Circuits in operation:

Thread:
https://www.therailwire.net/forum/index.php?topic=37285.msg482465#msg482465

Thats cool ... but the OP just wanted to detect a train and light a LED if the track is occupied ..  The arduino adds extra complexity ..

Having said that . I have an application for this setup

[ednadolski]

The arduino adds extra complexity ..

The arduino drives the bar graph LEDs and plays the audio prompt.   The transistor/detector circuit can be used without any of that, but actually I found it easier and more flexible than trying to build some other kind of dedicated/discrete logic.

Ed