# Low Cost Block Occupancy Detector



## Circuits4Tracks (Mar 26, 2012)

Do you like to build your own circuits from scratch, or do you just want something that is installation-ready? Or are you somewhere in the middle? Perhaps you want a kit with all the components needed and want to save money by doing the assembly yourself, or you have your own parts and only need a circuit board.

Circuits4Tracks aims to have what you need, regardless of where on this spectrum you are.

While there are tips and circuit diagrams for free, bare circuit boards, boards with components kits, and fully assembled circuits are also available.

At this time, we are offering a low cost Block Occupancy Detector. This detector can cost as low as $9.50 per block for a fully assembled unit, but costs go down from there if you want to do your own assemble, whether from a kit or using your own parts with our circuit board.

Our new circuit board design is about to go into production and you can get a special pre-order price for a limited time at http://circuits4tracks.daxack.ca


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## Carl (Feb 19, 2012)

Great lit items for the layout


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## plandis (Oct 5, 2011)

Circuits4Tracks said:


> Do you like to build your own circuits from scratch, or do you just want something that is installation-ready? Or are you somewhere in the middle? Perhaps you want a kit with all the components needed and want to save money by doing the assembly yourself, or you have your own parts and only need a circuit board.
> 
> Circuits4Tracks aims to have what you need, regardless of where on this spectrum you are.
> 
> ...


I like those!!


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## gunrunnerjohn (Nov 10, 2010)

plandis said:


> I like those!!


Doesn't look like it's applicable to O-scale.


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## plandis (Oct 5, 2011)

gunrunnerjohn said:


> Doesn't look like it's applicable to O-scale.


I know. but it gave me an idea of using mini toroid CTs on the center rail feeder wire on isolated blocks. Its just floating around in my head right now with no time to bench it. but with this multi channel DC current detector being so cheap (low cost) it got me thinking of a way to use it on AC. If someone comes up with low cost reliable block detection, wow.

what do you think about that idea John?


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## gunrunnerjohn (Nov 10, 2010)

I've thought about doing something like this, and the torrid coils are the way a GFI works, so that should be applicable to this use as well. I think a pretty simple circuit would do the trick, but I believe you'd be looking for low current AC from the torrid as it's going to simply be a transformer.


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## plandis (Oct 5, 2011)

gunrunnerjohn said:


> I've thought about doing something like this, and the torrid coils are the way a GFI works, so that should be applicable to this use as well. I think a pretty simple circuit would do the trick, but I believe you'd be looking for low current AC from the torrid as it's going to simply be a transformer.


I found some mini toroids from digikey. 100:1 with about 5 amp max primary (the hole). also found some mini reeds relay with 50ma coils. I'll put some back-to-back zeners across the coil to clamp the voltage so as not to over-voltage it. that should not hurt the CTs. then use the form C contacts off the reed relay. those are good for 5 amps. plenty for block detection. I have some of these goodies coming. when I get a chance to bench it up and "smoke test" I'll let you know. If these work, I'll have about six bucks per channel. that is as long as this detector remains passive.


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## Circuits4Tracks (Mar 26, 2012)

*Circuit Specs*

This occupancy detector is capable of handling a track load of up to 3 amps, and that may be DC, AC, or DCC.

The full specs may be seen at http://circuits4tracks.daxack.ca/Products.html


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## NIMT (Jan 6, 2011)

Is there any way to bump this up to handle 8 amps?


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## Circuits4Tracks (Mar 26, 2012)

*Increasing current capacity*

The circuit uses diodes to carry the track power from the common terminal to each of up to four track feeders. The 3 amp limit is from the use of 1N5401 diodes which are rated for a maximum of 3 amps continuous.

My first thoughts would be to use external diodes (or a bridge) that are capable of handling 5 amps to bring the total current capability up to 8, but another type of diode would not have the same operating curve and this would not likely result in a 3A/5A split of the current.

The better solution would be to replace the 1N5401 diodes with ones that are rated for 8 amps. The traces on the circuit board that carry track current should be capable of this current as I tend to lean towards the heavy side just to be sure. A quick look at what is available shows diodes rated at 8A that come in a TO-220AC case, which would require some lead bending to use on the circuit board. They tend to cost in the range of about $1.15 each (in quantities of 25) which is almost double the price of the 1N5401 diodes. Four are needed for each detector.

Another option would be to use a bridge rectifier, and I have seen some 8A models that are priced at just over a buck each, which is actually LESS expensive than the 1N5401 diodes (and involves one quarter of the soldering as only two leads need be soldered instead of the 8 of the discreet diodes!). Having a model with leads that can be bent appropriately would be the only issue.

If you are looking to source your own parts, the circuit boards are only $4.79 each (plus shipping). It is also possible to quote a special kit price that does not include diodes if you are sourcing your own. It may also be possible to look into sourcing an 8A diode and getting a price for a kit or assembled unit using these.


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## gunrunnerjohn (Nov 10, 2010)

Those TO-220 diodes for 8A would also need a heatsink, so that would have to be taken into account. Most high current bridge rectifiers also require a heatsink to operate at their maximum rated current.


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## Circuits4Tracks (Mar 26, 2012)

Yes, which is another reason why the bridge rectifier would be a better choice. It would still need a heat sink, but it wouldn't be as crowded as four TO-220 packages in the same space.


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## NIMT (Jan 6, 2011)

Thank you Circuits4Tracks!
That was exactly what I needed to know!:thumbsup::thumbsup:
We'll be in touch!


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## Circuits4Tracks (Mar 26, 2012)

*Version 4 Is Now Available*

Circuits4Tracks has released Version 4 of the Quad Occupancy Detector.

Version 4 is the same size, with identically located mounting holes, as the version 3 detector, but with three differences:

1) Now uses bridge rectifiers that allow up to 4 amps of track current (version 3 used 3A diodes). In addition to the higher current, a special order unit that uses 8A bridge rectifiers with heat sinks will soon be available. For those purchasing and assembling the kit form, the bridges have a total of 16 leads to solder instead of the 32 leads of the diodes.

2) The 6-pin header for outputs is duplicated with screw terminal blocks, giving you maximum flexibility for connecting its outputs to other systems.

3) The price has been reduced: Full units are now $35.99 and the kits are $19.99.

Quantity discounts are available and flat rate shipping costs apply: http://circuits4tracks.daxack.ca


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## Circuits4Tracks (Mar 26, 2012)

Circuits4Tracks now has the 8A version of the Quad Occupancy Detector available to order online. A built and tested unit sells for $44.99 and the kit is $25.99.

As a result of some customer feedback, we have also put together an "Add-on Kit" that is used *with* a Quad kit (regular or 8A) to produce two Dual Occupancy Detectors. The Add-on Kit sells for $5.49

As with all our products, quantity discounts are available when purchasing as few as three of the same item.

http://circuits4tracks.daxack.ca 

If ordering before August 31, 2013, enter the coupon code *ModelTrainForum* (no spaces, and upper/lower case matters) at the checkout to receive a 3% discount off the items you ordered (in addition to any quantity discounts that apply).


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