Voltage Problem?

BNSF Eldridge Jan 20, 2020

  1. BNSF Eldridge

    BNSF Eldridge New Member

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    Hi Y'all. I have an arduino and arduino motor shield v2. at the track with a 15v power supply I am getting 12.6 volts to the rails on a test track. I can throttle most locos without issue. However I cant read most of them for decoder pro. I have read that i will lose ~3volts from the shield. Would a bigger power supply fix this?
     
  2. Jimbo20

    Jimbo20 TrainBoard Member

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    Hi,

    You don't say what scale your layout is but this problem is often found with 'N' or smaller because the current drawn by a loco is less than the threshold of the CV reading software is set to detect.

    You could try changing the value of ACK_SAMPLE_THRESHOLD in the PacketRegister.h file in DCC++ from the default value of 30 to something smaller. Many have found a value of 15 to work but some have needed to take it down as low as 3.
     
    BNSF Eldridge likes this.
  3. BNSF Eldridge

    BNSF Eldridge New Member

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    Hey, thanks for the reply man. HO scale is my scale. Will try and do this tonight. Where is the latest official source ? people still using Github?
     
  4. sdcruz

    sdcruz New Member

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    Hi Guys
    I also get about 4 to 5 volts drop at the tracks using an Arduino Motor Shield! Well apparently the Arduino Motor Shield steals Voltage! It is a very poor (inefficient) performer due to the chip on it. If you dont wnat that type of power loss then look at getting a Pololu motor shield instead. Look at this from Costin's post - very interesting:
    https://model-railroad-hobbyist.com/node/37192
    Regards
    Shelton
     
  5. Quax

    Quax TrainBoard Member

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    Have you measured this using a simple multimeter (DMM) or a scope?
     
  6. sdcruz

    sdcruz New Member

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    Hi
    I used a simple MM - set to AC. I know its not accurate.
    Regards
    Shelton
     
  7. H0Guy

    H0Guy TrainBoard Member

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    Shelton: I am not sure what you problem is, but my Arduino Motor Shield works finE with maybe a 0.05 voltage drop, about the same as my NCE PowerCab.

    Beware of the Pololu. It doesn’t support standard HO Auto Reversers. It has its own overload circuit which trips in 12usec, much faster than most Auto Reversers.
     
  8. wvgca

    wvgca TrainBoard Member

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    12.6 volts on the tracks would mean about 11 volts after the decoder, as a maximum to the motor ... a little low but not terrible ..i think you should look elsewhere for your inability to read
     
  9. H0Guy

    H0Guy TrainBoard Member

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    That’s why the study you linked to had the power off issue. See all comments.
    Pololu May work fine without frog-juicers and Auto Reversers, but ....
    To my knowledge, many of the other shields out there have not been thoroughly tested with frog-juicers and Auto Reversers either, so if you use these devices, beware for now.
    I plan to use my Pololu on my standalone programming track and my Arduino Motor Shield on my layout which has two Auto Reversers.
     
  10. Jimbo20

    Jimbo20 TrainBoard Member

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    The op posted this over 6 months ago and didn't report back if changing the ACK_SAMPLE_THRESHOLD value made a difference. In fact he's not posted anything since!
     
  11. sdcruz

    sdcruz New Member

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    Hi All
    Yes I am aware of the auto juicers and reversers issue - but it is not a concern for me as I have neither.
    Regards
    Shelton
     
  12. Mike23

    Mike23 New Member

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    Hi H0Guy!
    If I understand well, You have Arduino with Arduini Motor Shield and the voltage drop is very low. (Less than 0.1V)
    I use Arduino Mega + Ardino Motor Shield V3. I Use 18V power supply but on tre track I have only 16.6V. I tought, it is normal, but after reading Your post, I am thinking about what I made wrong. This is a big problem to me, because some of my turnouts do not work on 16.6V but work on 17.3V what is the voltage of my Roco booster.
    So my question is only, that Your system is like I have, and You have only very little voltage drop? I mean if I compare the 18V DC power supply and the PWM signal.
    Thanks, Mike
     
  13. appCurious

    appCurious New Member

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    I am new to DCC. Thanks for keeping the DCC++ project alive as DCC++ EXtended. I really appreciate all of your work and efforts.

    My question is also about voltage. I have 0v on both program and main track outputs B, A after sending the power command <1>. I do receive a response <p1>

    Am i suppose to run a separate power supply to my track?
    Or is the main track output ( terminals A ) expected to have voltage on it all the time?

    I am able to send the command for power <1> and see the led's light up behind the terminals A and B. I am able to send the diagnostics command <D> and see them blink with dcc signal. During diagnostics I am able to read voltage.

    I am working with H.O. scale and using Gregg E. Berman original base station code ( mostly because i just found this and didn't know EX existed until last night ).

    My setup
    Arduino Uno
    DIY MORE Motor Shield HN ( jumpers between 10 & 12, 5 & 13, Vin pin removed to avoid back feeding voltage into Uno)
    15V 1.5A power supply
    Gregg E. Berman original base station code
    Serial Communication to send commands ( during testing )
    My own Web Server to send commands from User Interface

    Steps to reproduce
    send power command <1>
    no power on terminals A or B

    Thanks for your guidance,
    appCurious
     
  14. appCurious

    appCurious New Member

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    Well...I'll file my mistake under 'learning'...i was testing for dc voltage. i have the expected output of 16Vac
     
  15. Mike23

    Mike23 New Member

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    Hi appCurious! It is a good news, You found the solution. I was in the same situation too even after a lot of AC measuring, on another day I tried to measur DC and only after a lot of try I recognised my mistake. :) I think it is a common mistake.

    Tapatalkkal küldve az én Nokia 7.2 eszközömről
     
    appCurious likes this.

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