PWM train controller ...help needed

Discussion in 'General Electronics Chat' started by PrinzEugen, Jan 24, 2012.

  1. PrinzEugen

    Thread Starter New Member

    Jan 24, 2012
    13
    1
    from BDA's blog http://bda-train-blog.blogspot.com/2...ly-for-h0.html

    [​IMG]


    [​IMG]



    summary

    This controller feeds the analog railway system with PWM impulses, with fixed amplitude (12 - 14V) and variable width. This means that the output voltage goes from 0 to 12-14V and back to 0 with a 25 kHz frequency.
    Do NOT use it to drive digital locomotives, until you change the C1 capacitor with a 470nF one! This will lower the frequency of the PWM, so that the digital decoders will know for sure that they work on an analog railway sistem.

    - overcurrent above 1a and short circuit protected,

    - it can be used wit reverse polarity kipp switch for change direction

    - also no heatsink is needed for BD651 and LM7809, and all capacitors are ceramic, all resistors with at least 0.4w wattage



    so my problem....
    I have checked board for 7 time literary. All connections on board are like on scheme.

    Potentiometer doesn't working, stuck to 14v as input. No min or max.

    Readings are 14v on output. Led dont lit. Motor dead on 14 DC voltage
    No cold solder joints also.
    Output and input are not short connected.
    Positive input is on + rail (checked). Negative input is on - rail




    5-6-7-8-9 cd4093 to ground . 4 and 10 free pins


    Q1: BD651 transistor
    Q2: BC547
    C1: 1nF capacitor
    C2: 0.33 microF capacitor
    C3: 0.1 microF capacitor
    D1 and D2: 1N4148 diodes
    D3: 1N4007 general usage diode
    R1: 2.2 KOhm resistor
    R2: 2.7 KOhm resistor
    R3: 0.68 Ohm resistor
    R4: 1 KOhm resistor
    P1: 100 KOhm potentiometer linear mono

    Maybe pot is wrong connected ?...i dunno...capacitors dont have polarity also.
     
    meteor713 likes this.
  2. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,234
    Post a schematic.
    Your posted link doesn't work.
     
  3. PrinzEugen

    Thread Starter New Member

    Jan 24, 2012
    13
    1
  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    Show as the bottom side of your board.
    Also I don't see D1 and D2 on your board.
    And this SW1 it is a relay ?
     
    Last edited: Jan 24, 2012
  5. PrinzEugen

    Thread Starter New Member

    Jan 24, 2012
    13
    1
    i have d1 and d2 and one resistor...they are not on picture pot has blocked camera view. switch doesnt matter thats just late mod....
     
  6. PrinzEugen

    Thread Starter New Member

    Jan 24, 2012
    13
    1
    pot goes from 14.4 volt same as input as pot min..and 15.6 as pot max.

    power consumption of all circuit is 6.6mW


    all checked carefully and tested on short circuits and connections of other side of board....all ok.
     
  7. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    In which part of the circuit you did this measurement?
    And your voltage across pin 14 and 7 should be around 9V.
    So you need to show as the picture of the bottom side of your PCB

     
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