• Home
  • Exhibition
  • Activities
    • Photos
  • Location
  • Contacts
    • Email
  • Resources
    • Club history
    • Articles
      • Articles by topic
      • Anniversary train
      • Baguley Drewery in 009
      • Binns
      • Blackburn day out
      • Bluebell Railway
      • Blue Pullman
      • China visit
      • DCC without wires
      • Driving test
      • Dulverton
      • Electric Scots
      • Electronics lab
      • Exhibition hints
      • Exploding cars
      • Forty Years On
      • Garden railways
      • Garden railway down south
      • Giraffes on the line
      • The good, the bad & the ugly
      • Hornby Dublo Myta-Binns
      • Italian Railways Society
      • Kenneth Lamberton
      • Leicester & Swannington Railway
      • Lights, camera, action
      • Loads of coal
      • Machu Picchu
      • Magersfontein
      • ModelRail Scotland
      • Monsal Dale data
      • Monsal Trail
      • Norman Jackson
      • Observation Car Observations
      • Old stock on new track
      • Operating hoppers
      • Pechot-Bourdon in 009
      • Peterborough 2014
      • Railway Enthusiasts Club
      • Railway Widowhood
      • Rushby's Resins
      • Saltash
      • Scale and gauge
      • Shedloads
      • Sheep tennis
      • Sleepering in the Lakes
      • Sounds of the 60s
      • Sounds of the 70s
      • Warley 2011
      • Warley 2012
      • Warley 2013
      • Water Features - 1
      • Water Features - 2
      • Whisky Galore
      • Whither Westcott
      • The Wild Wood
      • York 2012
      • York 2013
      • York 2014
    • Short circuits
      • Short circuits - 1
      • Short circuits - 2
      • Short circuits - 3
      • Short circuits - 4
      • Short circuits - 5
      • Short circuits - 6
      • Short circuits - 7
      • Short circuits - 8
      • Short circuits - 9
      • Short circuits - 10
      • Short circuits - 11
      • Short circuits - 12
      • Short circuits - 13
      • Short circuits - 14
      • Short circuits - 15
      • Short circuits - 16
    • Friends of SMRS
    • NW railway links
    • Other links
    • Site map
    • Liverpool Bay
    • Archives
      • Newsletters
      • Talks archive
      • Club competitions
      • 2009 sleeper blog
      • 2008 sleeper blog
      • Project 2010
      • Project 2010 blog
      • Tranquility B/board
      • 40th Anniversary
    • Credits
8 Points of view - revisited

8 Points of view - revisited

Stacks Image 1039
Motor driven point changing systems normally require two wires to each point. Power is fed via a two pole  change- over switch which reverses the polarity across the motor, operating the motor in the reverse direction and changing the point. All that is required is a supply of 12 volts DC and one switch for each point. The diagram explains all.

Stacks Image 4416
Don't despair, there is a much more economical in wiring way to do it using that great saviour of us all, namely common return. First we need a power supply of +12 and -12v DC relative to a common earth. This can be derived from a single 16v AC source with the aid of two diodes and two capacitors. To control each point only a single pole change over switch is required. One terminal of the point motor is connected to the common earth and the other to the centre of the changeover switch. The other two terminals on the switch are connected to the +12 and -12v supply. Operating the switch changes the polarity of the connecting wire from positive to negative and the motor reverses.
As a bonus, if you connect a bi-polar (red/green) two leg LED in series with the wire to the motor, no resistor is required, and you will get an indication of which way the point is set.
  • SHORT CIRCUITS