Forums Power and Sound Power and Sound DCC
  • Topic: DCC++EX

    Back To Topics
    (0 rates)
    • September 1, 2021 7:23 PM EDT
      • Boulder, CO
         
      • Posts
        108
      • Thanks
        22
      • Thanked
        83

      Heck of a day - smoked an mcu with a rookie mistake

      That set me back half a day

      But I did finally get the lights working:

       

      ____________________________________

      Steve, Outdoor - DeadRail - G-scale

    • September 2, 2021 10:08 AM EDT
      • Boulder, CO
         
      • Posts
        108
      • Thanks
        22
      • Thanked
        83

      Some notes on the relay board I am using.

      1. on amazon: https://smile.amazon.com/gp/product/B0993CX9G5
      2. it measures approx. 100mA current to close the relay,  The feather has a 3.3V regulator with 500mA peak current output.
      3. it sources 2.2mA when the digital pin is set high to activate the relay, spec'ed max for a SAMD digital pin is 2.0mA.

       

      So there is ample 3.3v supply.  But the pin current is too high.  There is a 100 ohm current limiting resistor

      in the input circuit.  It's the part labeled "101" in the above image.  It's located between the input connector

      (VCC IN GND) and a jumper.  Do NOT confuse with the other resistor labeled "102", which is between

      the 2nd jumper and the relay.  Replace the "101" resistor with a 330 ohm part.  This reduces the drive

      current to 0.89mA, quite acceptable.

       

      Another note.  To attach the relay to the diag connector wing I used the spare 4pin grove connector.

      I cut off one end and attached VCC, GND and pin 6 according to the standard color code.

      Just before plugging it in for the 2nd attempt (1st was the time I smoked the mcu/relay!) I noticed the wires

      on the grove end didn't match the others on that board.  Double checked, they sent me on pack of

      grove cables with the wires in reverse order on the connectors

       

      If I had powered it up that way I probably would have smoked a 2nd mcu...

      Changed pins to proper order on cable connector and all worked.

       

      ____________________________________

      Steve, Outdoor - DeadRail - G-scale

    • September 3, 2021 5:10 PM EDT
      • Boulder, CO
         
      • Posts
        108
      • Thanks
        22
      • Thanked
        83

       

       

       

       

      This post was edited by Steve at September 3, 2021 5:20 PM EDT
      ____________________________________

      Steve, Outdoor - DeadRail - G-scale

    • September 3, 2021 5:21 PM EDT
      • Boulder, CO
         
      • Posts
        108
      • Thanks
        22
      • Thanked
        83

      #4449 is on the road:

       

       

      ____________________________________

      Steve, Outdoor - DeadRail - G-scale

    • September 4, 2021 12:13 PM EDT
      • Boulder, CO
         
      • Posts
        108
      • Thanks
        22
      • Thanked
        83

      The Bigboy REALLY doesn't like those R3 switches!  I cringe every time I run him on the train room track.

      His Dead Rail boxcar is complete:

       

       

      ____________________________________

      Steve, Outdoor - DeadRail - G-scale

    • September 6, 2021 4:22 PM EDT
      • Boulder, CO
         
      • Posts
        108
      • Thanks
        22
      • Thanked
        83

      I created a "schematic" that shows the connections of the DeadRail system at the module level:

       

       

      ____________________________________

      Steve, Outdoor - DeadRail - G-scale

    • September 6, 2021 6:09 PM EDT
      • Pleasanton, CA
         
      • Posts
        1,489
      • Thanks
        1,914
      • Thanked
        1,330

      that is a tall antenna? no tunnels?

    • September 6, 2021 7:16 PM EDT
      • Boulder, CO
         
      • Posts
        108
      • Thanks
        22
      • Thanked
        83

      Jim,

       

      It's 4 -1/2", built the tunnels extra high knowing they would have to clear antennas:

       

       

       

       

       

       

      This post was edited by Steve at September 6, 2021 8:28 PM EDT
      ____________________________________

      Steve, Outdoor - DeadRail - G-scale

    • September 6, 2021 7:34 PM EDT
      • Boulder, CO
         
      • Posts
        108
      • Thanks
        22
      • Thanked
        83

       

      ____________________________________

      Steve, Outdoor - DeadRail - G-scale

Forums Power and Sound Power and Sound DCC

    Icon Legend

  • Topic has replies
    Hot topic
    Topic unread
    Topic doesn't have any replies
    Closed topic
    BBCode  is enabled
    HTML  is enabled

Add Reputation

Do you want to add reputation for this user by this post?

or cancel

Ads by Google