Simple DCC Block Occupancy Detector

[D0260]

As I understand it, the bridge rectifier is positioned so that it feeds power to the block . If there is nothing in the block, no current flows, therefore no pd across bridge and no output from opto.

Absolutely correct

[m.levin]

That is neither how it is connected , nor how it works...

I agree, but I saw the tags A and B, top diagram, as feeds from rail A and Rail B, commonly used to describe Dcc track feeds. That's why I was arguing that it wouldn't work, using an opto Isolator.
If you would of simply shown that http://www.electronicsinfoline.com link first it would of made far more sense, but instead you went straight off and very rudely insulted me, over a simple miss understanding on MY part. Obviously you had seen that circuit before and know it was in series and I simply missed where you said it was in series.

[D0260]

No I hadn't seen that circuit before - Google found it when I looked because I couldn't persuade this site to allow a reasonable representation to be drawn using block character symbols.. It doesn't take any working out though to see its a current detector.

[m.levin]

Still doesn't explain why you were so rude.

[D0260]

Still doesn't explain why you were so rude.

I provided more than enough detail for anyone to see how it works, in simple terms, provided a link to a data sheet for the opto, provided the typical specs and considerations for for the components, and even provided an idea of prices ..
Then you come along with some impossible ideas of how it works , and then start arguning about current flow and current drawn..
My terminology is current flow to keep it simple, we could have been considering electron flow which is negative flow in concept.
Its one thing to ask for something to be explained because you don't understand, its entirely the opposite to rubbish the true and correct version , and try and substitute an impossible scenario and sell that as correct by yourself.

[m.levin]

I admitted I miss read and miss understood the circuit. But no matter what miss understanding, it is still wrong that you spoke to me as if you had caught me in bed with your mother. The best humans make mistakes.
I admit I have my tail between my legs, but you seem too stubborn to move from you perch and apologise for something that has seen to upset me.
I may not have made a direct apology, but if you want one here it is;
Sorry I have total miss understood and miss read and may have upset over my comments.
I may not have the knowledge of yourself and others, but 3 years on, I still got a lot to learn, I have and will make mistakes, is it not all part of learning?
Maybe a “m.levin you have got it all wrong, look again” would have been better then the numerous and continuous insults.
I we all work with some clever people, but even they need things putting in to idiot form, now and again and wouldn’t appreciate the type of insults you gave me.

[kbriffa]

Hello everyone......I am sorry I didn't realize it when I posted the initial circuit that this other diagram was also important to understand how the whole thing was wired up to the tracks.



Now that the components have been identified and we know how it should be wired to the track - what is next needed in the circuit (at X and Y) to be able to light an LED to demonstrate that the block has been occupied?

Would I have to follow the circuit suggested here http://www.electronicsinfoline.com/Proj ... tors.shtml as shown to the right of the opto-isolator or is there a simpler way?

Also I realize there will be a voltage drop - will it be so big as to affect the running of trains? Sorry for the many questions but I'm trying to get my head round this as best as I can.

Thanks in advance everyone once again for your help

Regards
Kenneth

[kbriffa]

You can design circuit diagrams using a trial copy of SmartDraw http://www.smartdraw.com/product/featur ... ve-Symbols.

Hope this helps in answering my questions.

Thanks
Kenneth

[kbriffa]

Okay. So after looking up suitable components and the discussion on this topic and other forums, I have drawn the following circuit. The whole point is to make that LED light up when the block is occupied (even when the engine is stationary).



Will it work? Does it make sense? Do I need to correct something? All comments are appreciated.

Thanks in advance for the help.

Kenneth

EDIT: The bridge rectifier will have to be replaced with 4x IN5401 (or 4x IN4002?)as my shop's catalogue doesn't list it.

[kbriffa]

Hi. So it's testing time. The first circuit I tested was a re-visit to the simple circuit I attached a few posts up



I had said that the cirucit only works when the engine is moving. Well, I tried to change diodes and I can confirm that the circuit works even when the engine is stationary. Please bear in mind that my layout is supplied by a Lenz LZV100 with the default track voltage of 16V and the Lenz TR150 transformer to give me a max of 5A.

I tried the circuit with a few different locos and the evident drawback is that the brightness of the LED varies with the type of loco placed on the block. Also when the loco is started or the lights are switched on the LED shines brighter. I will try this circuit again with IN4007s diodes instead to see if there's any difference and next try out the circuit which started this topic in the first post. Fingers crossed....

Kenneth

[Silver Surfer]

Hi Kenneth

Might be easier to buy one of these;-

DBD22 DCC train detector from Team Digital - knock out at about £20 each but you get two detectors on one board and nothing on it to reduce track supply.

Need a 12vdc supply but no physical connection needed to your track, you just pass a dropper wire through the hole in the black Bassetts Allsort looking thingy and away you go. Has outputs for remote LEDs.

Can be had from Bromsgrove Models in Birmingham or Sherwood Models in Nottingham

Mike

(Nb. Electrical terminology deliberately avoided for fear of reprisals).

[Son-1]

Hi Kenneth
Might be easier to buy one of these;-

How boring would that be. It's the challenge of building it yourself.

I've started acquiring parts to build one (and I'm not even DCC yet), and IF it all goes ****-up, I can fix it. Admittedly both the wife and myself have access to accounts with various component companies, so if RS or Farnell have it, we can get it at cost.

[kbriffa]

Hi Kenneth

Might be easier to buy one of these;-

DBD22 DCC train detector from Team Digital - knock out at about £20 each but you get two detectors on one board and nothing on it to reduce track supply.

Need a 12vdc supply but no physical connection needed to your track, you just pass a dropper wire through the hole in the black Bassetts Allsort looking thingy and away you go. Has outputs for remote LEDs.

Can be had from Bromsgrove Models in Birmingham or Sherwood Models in Nottingham

Mike

(Nb. Electrical terminology deliberately avoided for fear of reprisals).

Yes, this is a transformer-type detector. I had read something about them but didn't realize that they do not draw power from the track. That is a very big plus in my opinion. I will definitely have to consider this type of detector. Thanks for posting this. I will try it out after the other circuits (at the moment Bromsgrove say it's out of stock ).

Kenneth

[Flashbang]

Hi
As you seem good at electronics, have you considered joining MERG and building their kits?
They produce an 8 way non intrusive block detector for £22.50 /kit.
Similar to the ready made unit, but with 8 detection units. That's less than £2.83/unit !!!
You do have to belong to MERG by an annual membership fee, but the savings if you can assemble a basic circuit board are vast!
http://www.merg.org.uk/

[Gordon H]

Hi
Similar to the ready made unit, but with 8 detection units. That's less than £2.83/unit !!!
http://www.merg.org.uk/

The MERG 8 way 'DTC' unit also has the option to subdivided into 4 x 2 detectors or even 2 x 4 detectors if desired.