DCC++ Hardware - Block Detection

HVT Jan 27, 2016

  1. Kim Olsen

    Kim Olsen TrainBoard Member

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    More explanatory version: upload_2016-3-20_17-27-55.png
     
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  2. David Bodnar

    David Bodnar TrainBoard Member

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    Thanks for the details, Kim - I may give it a try

    dave
     
  3. hoyden

    hoyden TrainBoard Supporter

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    I like the idea of using the current sense transformer but dislike the cost. In 2006 when I built my detectors I used bridge rectifiers that cost less than $.50 each and quad opto-isolators. Current sense transformers were about $8 each. The tradeoff was the bridge has a 1.4V voltage drop and the current sense transformer has 0. In hindsight with 64 detectors the initial expense was less. Now I see the current sense transformers price is comparable. I plan to experiment with these transformers.

    Thanks for sharing!
     
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  4. Scott Eric Catalano

    Scott Eric Catalano TrainBoard Member

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    How about some pictures of the current sense detector? I am a picture example type of guy
     
  5. HVT

    HVT TrainBoard Member

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    Scott,

    Dave Bodnar has lots of info and pictures on his website at http://www.trainelectronics.com/DCC_Arduino/Current_Sense/index.htm I have some coils from eBay and will attempt to hook them up within the next week or so. (Out of town funeral followed by visiting grandchildren this week/weekend)

    Dave Merrill
     
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  6. Kim Olsen

    Kim Olsen TrainBoard Member

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    Currently the circuit is only of the bread board variety on my test bench, but I plan to make a few of them next week when I get my hands on some 10k pots ;-)

    Kim
     
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  7. Scott Eric Catalano

    Scott Eric Catalano TrainBoard Member

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    I've already done Daves current detection however he uses very light resistors....I need heavy resistors as I am using HO Scale and I've read that HO Scale uses 5-10k resistors on wheel sets if I am not mistaken. Dave models N Scale I believe.
     
  8. Kim Olsen

    Kim Olsen TrainBoard Member

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    I will upload some photos later today, as I described you can adjust the sensitivity, so it triggers at the load you desire.

    Kim
     
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  9. Kim Olsen

    Kim Olsen TrainBoard Member

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    Here are the diagram and some pictures of my prototype:
    DSC_0919.JPG DSC_0920.JPG DSC_0921.JPG upload_2016-3-22_19-18-40.png
     
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  10. Scott Eric Catalano

    Scott Eric Catalano TrainBoard Member

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  11. Kim Olsen

    Kim Olsen TrainBoard Member

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    Yes im using H0 scale trains, with a 15V power supply, and a Sprog 3 DCC controller (2.5A) as I dont have a arduino motor shield yet. This circuit will trigger with a 10kOhm value or less resistor across the wheels, which translates to 15Vrms/10kOhms=1.5mA=15V*1.5mA=22,5mW meaning a 1/16W resistor will be sufficient, so 1206 1/4W SMD resistors is more than enough. If you wnat more, or less sensitivity adjust the value of R3.

    ps.: The 10k resistor on the arduino I/O pin in the diagram, represents the internal pull-up resistor.

    Kim
     
    Last edited: Mar 22, 2016
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  12. Scott Eric Catalano

    Scott Eric Catalano TrainBoard Member

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    What does your arduino sketch look like for the block detector? I've been thinking about purchasing a Sprog 3 also.
     
  13. Kim Olsen

    Kim Olsen TrainBoard Member

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    I use the standard DCC++ sketch and i have just configured the sensor input in JMRI, in the DCC++ options tab, but you can do it with the serial monitor commands in arduino IDE aswell ;)
     
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  14. Scott Eric Catalano

    Scott Eric Catalano TrainBoard Member

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    Oh ok...didn't know if it was stand alone or not.....I like to keep everything separate, signals, sensors, detectors...less chance of things going wrong...in case one thing goes down it does not affect anything else.
     
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  15. Kim Olsen

    Kim Olsen TrainBoard Member

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    Oh I see. Well I have just begun to dive into the arduino and dcc++ world, but I suppose you could use a separate arduino uno to each category, and connect them all to your pc, or daisy chain them somehow?
     
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  16. sboyer2

    sboyer2 TrainBoard Member

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    rfid sensors for arduino are $3 at most (http://www.ebay.ca/itm/130892542303) $2.47usd and free shipping and word very well and it is both a reader and a writer. and come with 2 writable 1KByte tags

    Steph.
     
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  17. Desiro

    Desiro New Member

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  18. Pepijn

    Pepijn TrainBoard Member

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    Can anyone comment on the differences and pros/cons of the two different circuits posted by Kim and David? I'll be trying out the both of them as soon as parts arrive.
     
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  19. Kim Olsen

    Kim Olsen TrainBoard Member

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    Well in function, the only difference is sensitivity I suppose. I designed the circuit with high sensitivity, low cost and low number of components in mind. I tried to include a rectifier bridge in the final version (mb6s) but the results were unsatisfactory; all the sensitivity went out the window. So the final version ended up with 4 1n4148's which are dirt cheap anyway. I found some cheaper current coils from China with a unit cost of about 1.5$ which brings the total cost per sensor unit down to about 2.2$, and a fabrication time of about 10 minutes per sensor. I will post some pictures of the final results later, they have already been incorporated into my layout.

    Kim
     
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  20. TwinDad

    TwinDad TrainBoard Member

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    Kim, why do you think the MB6S didn't work where the 1N4148s did?
     
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