Block Detectors 101
#1
I have been given an NCE Power Pro block detector to use as a detector for a RR crossing and signal system which I had bought at some "dodgy" stall at a train show a while back.
The old system used light or IR sensors as detectors, but now I need to know what is needed to make this new block detector work.
And to try to get a handle on what the description...."The logic output of the detector is open collector means, which I assume is the basis of all understanding.
So if anyone can tell me slowly enough, and in single syllable words what it all means and what "signal systems logic" is all about I would be forever in their debt.
I have lengths of isolated rail either side of the crossing so I be thinking block detection is the way to go here.

here is a pic of the said block detector
[Image: ef959913.jpg]

Speak slowly now, so I can follow. Tongue

Thanks for your patience.

219
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#2
OBJack Wrote:And to try to get a handle on what the description...."The logic output of the detector is open collector means, which I assume is the basis of all understanding.

While I've never heard the term " Open Collector ", used in logic circuits......digital, as I learned it, assigns "high" (open circuit voltage) to "1", and "low" ( short to ground ) to "0".
If the collector of a transistor is "open" it's " output " is the applied operating voltage ( typically 5 Volts DC ), and is a "1" or high.

The other thing I learned about logic circuits is that a "1" or "high", is a "true statement".
So......
If the output of the detector is "Open Collector / high /"1"/"true", then there is something in the block.
If the output of the detector is "closed ? collector" / low / "0" /false, then the block is empty.

Only something in the block that draws current. ( loco, lighted car, or cars with resistive axles "resistor wheel sets" ) will cause the detector to output " Open Collector" / etc.. Rolling stock that does not have some form of current drawing capability, is, "invisible" to the detector.
Hope that helps.
We always learn far more from our own mistakes, than we will ever learn from another's advice.
The greatest place to live life, is on the sharp leading edge of a learning curve.
Lead me not into temptation.....I can find it myself!
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#3
Thanks for the reply Sumpter.
So I can gather from that, that the detector can sense when something is drawing current on the block it is looking at and ( here's the crunch) ..can therefore send what?????....... a signal/package of digital info?... to whatever it is controlling to turn it on/activate it/throw a switch??
It will not be current huh? ie: to turn on flashing signal lights.
So I guess I am looking for the system/hardware/software that it will drive.
I see that I cannot just hook the two output wires up to a set of lights and they will come on when a train draws current from the block it is hooked into.
The two output connections from the block detector in the diagram, are labeled to go to "Ground" and Logic (+) at the signal logic circuitry

I guess I have confused the issue somewhat now, but I need to know what I plug these two wires from this block detector into be it to make the loco stop at a station, not enter an occupied block or for signals to work etc.
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#4
OBJack Wrote:Thanks for the reply Sumpter.
So I can gather from that, that the detector can sense when something is drawing current on the block it is looking at and ( here's the crunch) ..can therefore send what?????....... a signal/package of digital info?... to whatever it is controlling to turn it on/activate it/throw a switch??
It will not be current huh? ie: to turn on flashing signal lights.
So I guess I am looking for the system/hardware/software that it will drive.
I see that I cannot just hook the two output wires up to a set of lights and they will come on when a train draws current from the block it is hooked into.

From what I can read in the picture, it looks like there is an LED included that can be driven by the device to indicate block occupancy. However, the wording on whether it can drive higher voltage or heavier amp draw is obscured - although I am guessing you are right in that it will have to trigger a separate relay or other device for things with heavier loads or different power requirements that what is supplied.

So all that to say -- if all you need is crossing signals, it might just do it.

Andrew
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#5
Thanks for taking the time Andrew,
MasonJar Wrote:From what I can read in the picture, it looks like there is an LED included that can be driven by the device to indicate block occupancy. However, the wording on whether it can drive higher voltage or heavier amp draw is obscured - although I am guessing you are right in that it will have to trigger a separate relay or other device for things with heavier loads or different power requirements that what is supplied.

So all that to say -- if all you need is crossing signals, it might just do it.
Andrew

Yes you are right about the LED, but in the diagram it is powered from an outside source and uses two other output connectors on the block detector, and from what I can see is not necessary to operate the device, (However what do I know) :?
It seems that no current is generated by this block detector for it to be able to run a set of signals... but maybe relays information somehow, to another module/device/decoder that opens a switch to start whatever it is (Xing Lights in this case) that it controls when it is sent info that there is a current draw in the block that the detector is hooked into. phwew.
So I am thinking there has to be 3 things to make this work
1. A block detector to send a signal to...
2. A module/controller/decoder? that will close a switch to turn on...
3. A set of signals which will light ......
...............until the current draw has gone, & the block detector sends a message to the controller/module/decoder to open the switch and stop the lights working.

So if this is correct... what is the #2 Item that I'm looking for? I guess an automatic switch controller for an accessory with its own power source.
S'cuse my ignorance, Brains gone dead...
Gawd it sounds like a dogs breakfast, but Lenz (the system I'm using) will have a number for it like an LZR 167. Nope

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#6
OBJack Wrote:The old system used light or IR sensors as detectors, but now I need to know what is needed to make this new block detector work.

Light, or IR sensors, are usually set up with a light / IR source ( emitter ), and they are "on" and drawing current from the
"crossing and signal system". When the light is "interrupted" the sensor stops drawing current, and it goes high/"1"/ true, and the signal system responds by lowering the gates. ( or changing the signal from green to red, however it is set up for )
Your "block detector" replaces that light/IR sensor (two outputs "to signal system" ). The Signal system provides the power, that the block detector uses.
The wire "from booster to track", carries track current. The "device" that the wire goes through is virtually a transformer.
When something draws track current, the "transformer", induces a current, in its secondary winding, that activates the "Output to the signal system", and the signal system does the rest.
Instead of sensing a light level change, this block detector senses track current changes. because of this it is more reliable.
With light detectors, the crossing gates could come down just because your hand blocked the light.
( or an "under the influence" LPB, fell on the detector !! :o Big Grin )
Hope I've shed some "light" on the subject. Icon_twisted
We always learn far more from our own mistakes, than we will ever learn from another's advice.
The greatest place to live life, is on the sharp leading edge of a learning curve.
Lead me not into temptation.....I can find it myself!
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#7
Thanks for the reply Sumpter, and you did talk real slow so I could understand but...
I thought that if I wired the two output wires from the block detector ( The "ground" and the Logic +") into the same connections from where the replaced IR detectors wires had been I would have a functioning system
The answer is no. Could I have possibly fried the block detector?
I cannot detect any current coming from the two output wires of the block detector, only a resistance. Should I ?
Is this correct?

Would/could the system used by the signals to turn on with IR, the same as with the block detector's method?

Confusing all and sundry now I s'pose. Sorry for being a fat head.
Maybe there is an input logic + system that connects to the signals, to accept the output logic+ of the block detector to make them work?

You can give up on me if you like..

219
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..... Abandon the search for truth
Look for a good fantasy
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#8
"Thanks for the reply Sumpter, and you did talk real slow so I could understand but...
I thought that if I wired the two output wires from the block detector ( The "ground" and the Logic +") into the same connections from where the replaced IR detectors wires had been I would have a functioning system
The answer is no. Could I have possibly fried the block detector? "

If the block detector ground is connected to the signal system ground, and likewise plus to plus, the signal system should respond to the changes in the block detector.
"I cannot detect any current coming from the two output wires of the block detector, only a resistance. Should I ?
Is this correct? "

Only resistance, when not in the system.
if you're getting only resistance across those wires, connected to the system, and powered up ?....... :oops:

"Would/could the system used by the signals to turn on with IR, the same as with the block detector's method? "
Look at it this way....Both the IR, and the block detector, are "remotely operated switches".
In the case of the IR, the finger, is light. in the case of the block detector, it is current drawn by something on the tracks.
The best way of testing the block detector is to hook it up to the system, and monitor the voltage, across the wires where they connect to the system, with empty track, and then with a loco. If there is no change? make sure the polarity is correct, and if that's OK, then put the IR in and check voltages with, and without light. If there is still no change, the problem is in the system, not the "sensors". ( or both sensors are defective )

Confusing all and sundry now I s'pose. Sorry for being a fat head.
"Maybe there is an input logic + system that connects to the signals, to accept the output logic+ of the block detector to make them work? "
I have been given an NCE Power Pro block detector to use as a detector for a "RR crossing and signal system which I had bought at some "dodgy" stall at a train show a while back. "
"That", is "your system"......and may be your problem. Did that system work, with the IR ?
A quick check of the system can be done with a single diode ( just about any will work ). With the system on,and the sensor removed, touch the diode leads to the connector where the sensor had been, and note what the systems reaction is, then reverse the diode and see if any change occurs. You should get a "block occupied" indication, on one of the two attempts
Most diodes have a dark band at one end, that is the " + " end. It might have the schematic symbol for a diode printed on it, the "solid triangle" is the " + " end.


"You can give up on me if you like.. "
Not yet... Big Grin
We always learn far more from our own mistakes, than we will ever learn from another's advice.
The greatest place to live life, is on the sharp leading edge of a learning curve.
Lead me not into temptation.....I can find it myself!
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#9
Thanks for your help Sumpter. (My bet is you were are a teacher)..It is very informative and I am following your post and still experimenting.
The system works with the I/R detectors.
I don't know how to monitor the voltage..
...The best way of testing the block detector is to hook it up to the system, and monitor the voltage, across the wires where they connect to the system, with empty track, and then with a loco. If there is no change? make sure the polarity is correct, and if that's OK, then put the IR in and check voltages with, and without light. If there is still no change, the problem is in the system, not the "sensors".
( I have a multimeter..) The way I do it, nothing changes.

I hook the Block detector leads in where the I/R leads went in to the system.

Maybe I should take a deep breath and a cold shower/... and then go and buy a complete new signaling system and start from scratch, so as to let you keep your hair. Misngth

I am still workin' on it, but can only get to fool around with it on some weekends at the moment, so things move rather slowly... Sorry.

Jack 219
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