Announcement

Collapse
No announcement yet.

Two way single lane power switching circuit

Collapse
This is a sticky topic.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Two way single lane power switching circuit

    So you’ve got this super-duper twisty single lane mountain climb thought up or maybe a narrow chair rail shelf that runs from yer TV recliner over to the beer fridge that would be just great for sending a slot car on a brewski run without having to get up (sorry, you’ll have to figure out the beer dispensing part on your own) and you’re thinkin’ to yourself “geeze, wunnit be great if I could have my car run out to the end of this h’yar single lane track and then turn around and come back??!” Now you could put a little loop at either end to turn the car around, but the power is going to be backwards to what’s needed for the return trip. Enter the automatic power switching circuit.

    All the components are inexpensive and readily available online or at an electronics shop; and the circuitry is pretty straightforward (no programming, digital controllers, JK flip flops or even transistors or diodes). Just simple normal open (NO) or normal closed (NC) switches (either optical or mechanical type) for sensors and a 12 volt triple pole double throw (3PDT) relay.

    A 3PDT relay is just three two-way switches (each has one input, two outputs) ganged together and all operated by one solenoid (electromagnet). The relay has 11 blade connections (pins) on one end. The inputs to be switched are connected to pins 7, 8 and 9. Applying 12 volts across pins 10 and 11 will activate a solenoid. When the solenoid is inactive, the inputs connect to the normal closed side of each switch output on pins 1, 2 and 3; when the solenoid is active, it pulls the relay switches closed connecting input to output pins 4, 5 and 6.


    Here’s a simple single lane track with a loop at either end. The slot where each loop feeds back into the main track should have some sort of spring gate to keep the incoming car from heading up the wrong slot at the junction.



    The sensor switches that tell the relay when to switch are marked S1 and S2 on the diagram; they are located at the start of the short section of dead strip (no rails) just before the loop merges back into the single track. The dead strip should be at least a couple of inches long to give the relay time to switch before the car gets power

    Let’s take a look at how the electronics work:



    The 12 volt power source (or whatever voltage you’re running your track at) comes in at the left of the diagram. The top inputs to the relay are set up as a latching circuit, meaning that when it is switched on (power applied to pin 10), it will stay on until it is reset. In this case S1, a normal open switch will switch the relay on, and S2, a normal closed switch, will reset the relay when S2 is opened.

    In the initial state when power is turned on, S1 is open so no power goes to the solenoid input pin (10), meaning it is inactive and all the switches are in their Normal Closed position: input pin 7 connects to output 1, input 8 to 2 and input 9 to 3. For the variable voltage through the controller input (pin 8), the output (pin 2) connects to the right rail when traveling left to right. For the ground source input (pin 9), the output (pin 3) connects to the left rail when traveling in the left to right direction. In this initial state, the car will be traveling left to right on the main section of the track.

    When the car goes around the right hand loop, it momentarily closes switch S1 this sends 12V to pin 10, which activates the solenoid to connect pin 7 (12V in) to pin 4 out. Because pin 4 output is looped back to pin 10, the relay latches in the active position until it is reset (described below). The variable voltage input (pin 8) is switched to pin 5, connected to the right rail when looking in the right to left direction. The ground connection input (pin 9), is switched to output pin 6 which goes to the left rail when looking in the right to left direction.
    The car travels through the gate now going right to left on the single track.

    When the car goes around the loop at the left end, it opens S2 (the normal closed switch) which breaks the latching current to pin 10 to reset the circuit back to its initial state, with the car again traveling left to right.

    The astute observers out there will have noticed that the right hand rail when traveling left to right is the same thing as the left hand rail when going right to left – this means that we can jumper pins 2 and 6 together and pins 3 and 5 together (as indicated by the dashed red/gray lines in the diagram). Because these pins are ganged to their opposite switch position the ground on one can never* get connected to the power on the other.

    * unless there is a catastrophic breakdown in the relay’s internal parts – very unlikely but not unknown to occur, hence the reason you ALWAYS have a fuse in the circuit.


    more to come - stay tuned
    Scott

  • #2
    Two way circuit

    OK, we talked previously about a single lane out and back, what about if we make our single lane track a complete loop instead? Can we design that loop to automagically switch the direction a car travels around the track every lap and a half? What use is this? It effectively doubles the lap length and equalizes the number of left and right hand turns (the track I intend to use this on is for tuning proxy race cars, so testing for similar left and right handling qualities is important).

    Adding a pair of standard automotive relays plus a couple of lane changers (salvaged from spare digital track pieces or fabbed from model railway parts) to the previously described out and back setup performs this direction change.



    Looking at the simple layout above, the system works as follows:

    • Sensors S1, S2 and lane changer LC 1 (red) are only active when the car is traveling clockwise around the track; sensors S3, S4 and lane changer LC 2 (green) are only active when the car is travelling counter clockwise.
    • Starting (arbitrarily) in the middle of the longest (top) straight, heading clockwise (to the right)
    • Car passes sensor S3, nothing happens (S3 only active in counter clockwise direction)
    • Car passes lane changer 1 (LC 1), LC 1 is not triggered so car remains on main track
    • Car passes sensor S1 which triggers LC 1
    • Car continues around the track, when it arrives at LC1, which has been triggered by S1, it is diverted into the lane change segment.
    • Car passes sensor S2 which switches the polarity of the rails on the main track, which also activates S3, S4 and LC 2, and de-activates S1, S2 and LC 1.
    • Car returns to the main track, now travelling in the counter clockwise direction; the triggering sequence is repeated with S3, LC 2 and S4

    The lane changers require a light spring to return the flipper to open (straight through) position when not triggered (i.e. no power to the solenoid).

    In the electronics diagram I’ve broken the circuit down into two parts, the Power Latching circuit and the Lane Changer circuits. First the Power Latching circuit:



    The 12 volt power source comes in at the left of the diagram. In the initial state when power is turned on, S4 is open so the solenoid is not active, so all three switches in the relay will have their inputs (pins 7, 8 and 9) connected to their Normal Closed output pin. For, the ground connection (pin 9), this will be pin 3 which goes to the left rail when looking in the clockwise direction. For the variable voltage through the controller (pin 8) it will be pin 2 connected to the right rail when looking in the clockwise direction. For the 12 volt input (pin 7) this will be pin 1 out to the clockwise to counter-clockwise lane changer circuit LC1 (described below).



    When the car goes past S1 in the clockwise to counter-clockwise lane changer circuit, S1 closes, sending 12volts to pin 86 which activates the relay sending the 12V at input pin 30 out through pin 87. Because this output is looped back to pin 86, the relay latches to keep its 12V output on regardless of the state of S1 (which will open as soon as the car passes). The latched 12V output from 87 activates the lane changer solenoid, moving the lane change flipper to redirect the car into the lane change segment when it arrives at LC1.
    When the car enters the lane changer at LC1, it momentarily closes switch S2 in the Power Latching circuit, sending 12V to pin 10 of the relay in the Power Latching circuit, which activates the solenoid. This switches the 12V input at pin 7 to output pin 4. Because pin 4 output is looped back to pin 10, the relay latches in the active position until it is reset (described later). The 12V output from pin 4 also goes out to the counter-clockwise to clockwise lane changer circuit. The ground connection switches to pin 6, which goes to the left rail when looking in the counter-clockwise direction. The variable voltage through the controller is switched to pin 5, connected to the right rail when looking in the counter-clockwise direction.

    Because power is no longer going to the clockwise to counter-clockwise lane changer circuit, LC1 resets to normal (main track) position.

    The car is now travelling counter-clockwise around the track.

    When the car goes past S3 in the counter-clockwise to clockwise lane changer circuit, S3 closes activating lane changer LC2. When the car enters lane changer at LC2, it momentarily opens switch S4, breaking the latching current to pin 10 which resets the relay back to its initial state and the car ends up again travelling clockwise.

    Will post some pix when I get this thing up and running.

    cheers
    Scott

    Comment


    • #3
      This should be pinned to the top!

      Comment


      • #4
        I agree.

        Comment


        • #5
          Nice idea! Great!

          Comment

          kadikoy escort kartal escort
          eurocasino
          sisli escort mecidiyekoy escort
          sex vidio
          antalya escort
          lara escort escort istanbul escort sirinevler escort antalya
          pendik escort
          izmit escort taksim eskort lara eskort bayan bakirkoy bayan eskort
          gaziantep escort
          atasehir escort
          antalya escort bayan escort atakoy
          izmit escort
          ankara escort
          porno
          Working...
          X