1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

3 aspect model RR signalling help plse

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by angie1199, Nov 15, 2009.

  1. angie1199

    angie1199 New Member

    Joined:
    Dec 29, 2005
    Messages:
    243
    Likes:
    0
    Location:
    Essex, UK
    HAPPY CHRISTMAS MrDEB AND PETE
     
  2. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
    MERRY Christmas to all on Electro-tech
     
  3. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
    twin t revision

    here is the circuit you have built.
    can't figure out how you get a dim LED.
    I changed the track resistor from 10 - 10k
    I get very little current draw at am3.
    what LEDs and how much voltage do you have at VF2 with and without loco?
     

    Attached Files:

  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Raiway Pete

    Raiway Pete New Member

    Joined:
    Nov 25, 2009
    Messages:
    120
    Likes:
    1
    Location:
    Slovakia

    MrDeb Angie. I have about 900 Ohms in T4s collector circuit and an LED. Also the cap C3 is too small. 47 to 100 yF works well.

    Vcc = 11.5
    T4 collector no detect = 10.5
    T4 collector detect = 0.05

    C3 = 100yF or 47yF.

    During no-detect that means I have about 1 volt across the LED and the 900 Ohms. that's not enough current (1.6 Ma) to turn it on. Track resistance make no difference.

    Locos.
    Angie are you just putting two locos on a test track and having them stand there or are you actually running them. The decoders in quiescent state have high resistance, and its the decoders that contrll the motors.

    Also have you measured your relay coil resistance yet. If they are 12 volts and have a coil resistance of over 650 ohms they should work. In the mean time put a 1K resistor in series with the LED. 550 Ohms is a little low and you are exceeding the upper 20Ma limit just a bit.
     
  6. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
    TINA sim is close to actual

    at T4 collector
    no detect = 82.6mv
    detect = 11.91
    using 550 for LED resistor as the meter AM3 shows 18.77ma
    with 1k = 10.39ma
    on the relays, most 12v relays I have seen are 400 ohm.
    thinking a reed relay might be better?
    need to research cost of 12v relays vers 5v relays
    could be different?
    also reed vers coil relays.
    I wonder about a resetable fuse in case of derailment?
     
  7. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
  8. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
    We have a winner!

    using Petes revised circuit and the signal circuit that started this thread we , pretty sure, have a winner.
    using the small relays (see link I posted) for 320 ohm relays.
     

    Attached Files:

  9. Raiway Pete

    Raiway Pete New Member

    Joined:
    Nov 25, 2009
    Messages:
    120
    Likes:
    1
    Location:
    Slovakia
    Seems to be OK. Reed relays usually are a lot cheaper as they are nothing but a reed switch wrapped in a coill. They're also designed for low current operation.

    Resetable circuit breakers are available for DCC. They are super fast and also super expensive. However the track is protected but the trackside accruments with their own power supply should have something simple as a safety device.

    Angie,
    I don't think there is any place on your layoout that will need 16 amps at 230 volts AC, But try the 400 ohm coils. I think the 2N3904 can deliver OK. If that works your problem is solved for a few blocks anyway.
     
    Last edited: Dec 25, 2009
  10. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
    n channel mosfet?

    I tried to sim using 500 ohm relay coil - won't switch on.
    got to wondering if maybe a mosfet would have less internal resistance thus taking the signal detect switch to zero ground.
    Seeing how a NPN transistor won't do the deed. A relay with very little coil resistance(seems like anything over 350 ohms won't switch on.
    would a n chammel mosfet do the deed?
    tried a 2n6755 in Tina sim and it worked but that mosfet is for lots of current.
    never worked with mosfets but mat be an alternative to using relay?
     
  11. Raiway Pete

    Raiway Pete New Member

    Joined:
    Nov 25, 2009
    Messages:
    120
    Likes:
    1
    Location:
    Slovakia
    MrDeb,

    Are you sure the 500 Ohm relay coil was a 12 volt relay. The voltage swing I have here is from 0.5 volts to about 11. If it's a 12 volt relay it should latch. The 3906 should be able to handle 25 Ma or so easily.

    PS

    I also strongly sugwest that you put a diode across the relay couils to prevent back EMF from damaging the driver transistor.

    P.

    P.
     
    Last edited: Dec 26, 2009
  12. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
    yes on the diode.
    I am just inserting different componet to see what works.
    pretty sure its a 12v relay.
    not sure if I can designate voltage?
    will check back
     
  13. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
    relay parmeters

    no voltage designation?
     

    Attached Files:

  14. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    35mA in 100 ohms is 3.5V. It's a "5V" relay.
     
  15. angie1199

    angie1199 New Member

    Joined:
    Dec 29, 2005
    Messages:
    243
    Likes:
    0
    Location:
    Essex, UK
    Ok guys, here we go.

    As I said I didn't think I had a capacitor, but now I have a 105 capacitor stripped from the microwave circuit board.

    With this from MrDEB, http://www.electro-tech-online.com/attachments/twn-t-revision4-png.36676/

    Loco1 activates this circuit brilliantly, stationary or moving.

    However loco2 still has greens lit when on the block. When stationary the greens are as bright as red and yellow. When moving, greens dim more but still fairly bright.

    Loco2 obviously uses different amount of current.

    If I put a 1K resistor across the tracks while Loco2 is on the block, signalling works fine but the signals remain active if the 1K resistor is there when Loco2 is removed.

    So would I need a higher or lower resistance across the track to make it more sensitive or should I put a resistor in Loco2 between the wheel and decoder pickup?

    VF2 = 9.55V
     
    Last edited: Dec 26, 2009
  16. angie1199

    angie1199 New Member

    Joined:
    Dec 29, 2005
    Messages:
    243
    Likes:
    0
    Location:
    Essex, UK
    With LOCO1 VF2 = 9.15V

    With Loco2 VF2 = 9.55V

    No Loco VF2 = 10.6V
     
  17. angie1199

    angie1199 New Member

    Joined:
    Dec 29, 2005
    Messages:
    243
    Likes:
    0
    Location:
    Essex, UK
    Yay!!!!!!!!!!! We have victory. :D

    Added two signal diodes to green ground on each block.

    Changed resistor R8 to 2.2K.

    Works great with both locos and dry finger across rails.

    Tried 10R resistor across rails. Worked but smoked :(

    Have no idea what I was doing but it works. Now need to find out what power each wagons axle resistor has to be so it doesn't burn out and that's something else I don't know how to do. :)
     

    Attached Files:

  18. Raiway Pete

    Raiway Pete New Member

    Joined:
    Nov 25, 2009
    Messages:
    120
    Likes:
    1
    Location:
    Slovakia
    Hi Angie,

    Glad you have success. The two diodes in the emiters lifted them up to meet the cut off level at their bases.

    To get the axle resistor value (1 per car, I guess) Put 10K across the track. If it works increase the resistance until it the circuit stops detecting. Reduce the value by 10% to give you some slop. That is the value that each car has to supply across the track.

    To calculate the wattage use this. V²/R . If your DCC is 16 volts and your max resistance is 10K ohms V²/R = 16v×16v / 10000ohms. =1/40 watt

    If the max resistance is 1K then V²/R would be ¼ watt.

    I would also increase the signal LED resistances to 680 ohms. At 470 ohms you are putting about 24 Ma through each LED. That is 20% higher than the max rating of most LEDs. 680 ohms will reduce the current to about 15 Ma. That won't dim the LEDs much. My signal LEDS have a max rating of 20Ma. I run them at 7Ma with excellent results.

    P.

    Pete
     
    Last edited: Dec 27, 2009
  19. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
    R8 is the yellow LED resistor. At 2.3K how does it even light? unless we are talking about two different resistors.
    my last post I failed o change the relay coil resistance. the posted pic was the default relay. sorry for false posting.
    glad to hear you got it working.
    post a finalized schematic. Oh yea we still have the relay issue to deal with.
    look at the reed relay I linked to from Rapid electronics.
    The 5v = .62p and the 12v are .72p
    you could go with either one as the max voltage is really a wide swing.
     
  20. MrDEB

    MrDEB Active Member

    Joined:
    Apr 16, 2007
    Messages:
    4,364
    Likes:
    22
    ONLINE
  21. angie1199

    angie1199 New Member

    Joined:
    Dec 29, 2005
    Messages:
    243
    Likes:
    0
    Location:
    Essex, UK
    Ok here we go.
    Maximum resistor across track = 470K
    Less 10% = 423000R
    V x V = 256
    (V * V) / R = very tiny, so tiny my calculator can't work it out.

    Sound about right? Most resistors I have are 0.6 Watt.

    I've increased LED resistors to 628R and yes, they didn't reduce in brightness noticeably. They are 2V - 2.2V (max 2.5V) with max current of 25mA, typical of 20mA.
     

Share This Page