Sensor for train

[gk99]

want to turn on dc motor when train goes by and turn off motor when train goes by another sensor down the track. I am turning on a water wheel and motor only has to go forward. I can use a timer set up also , around 10 to 15 seconds. thx

[groundFungus]

Not sure what your question is, but here is a MOSFET motor driver. Pick a MOSFET that can handle the stall current of the motor.

Using millis() for timing, a tutorial.

Several things at a time, another millis() timing tutorial.

[groundFungus]

For the sensor(s) you could use a light gate. Google "light gate arduino" for more information.

Or attach magnet to the train and use Hall Effect sensors.

[sterretje]

Adding to post #3

Current sensing
Reflective IR sensor

[JohnRob]

@sterretje

Reflective IR sensor

I would think the reflective IR sensor would be a good choice. You could put a small mirror ( < 1/4" sq) on the bottom of the engine or 2nd car. the sensor would peak through a hole inside the tracks.
If you find other lights are sensed by the receiver simply pulse the LED and verify the reflected signal is pulsing at the same frequency.

[anon57585045]

What scale? I'm assuming a model but in fact you didn't say... Size does influence the choice of solution somewhat.

[paulpaulson]

Hello,
make a basic design using a H-bridge and a sensor for current per rail track and test.

[gk99]

ho scale -

[dave-in-nj]

Part of the answer lies with what is visually acceptable

I would get an IR sensor and put it under the track have it look up
When a trane passes check results.

You could hide in shrubbery
You could hide in bridge overpass
Hide in sign posts.
Or in rocks

[gk99]

dave - you helped me before , have another project that I need help with.

I am building HO Scale coal dumper with a linear threaded rod that I am turning with a 6vdc N20 motor. It will position a coal car to the dumper by pushing it on the linear track with a servo arm . The servo SG90 will move arm 90 degrees to go between cars to position them for the next coal dumping movement. How can I have the servo go 90 degrees with a push button that I can push 1 time for the arm on servo to go down and then push another button for servo arm to come up ?
I have a mega 2560 and Nano Boards.
THX
GK

[groundFungus]

Can the same button run the servo to 90 on one press and back to 0 with another press?

Like this example?

// press button once servo to 90°, press again servo to 0°.
// by groundFungus aka c goulding
#include <Servo.h>

Servo servo;

const byte buttonPin = 12;
const byte servoPin = 7;

bool buttonState = 0;         // current state of the button
bool lastButtonState = 0;     // previous state of the button
bool mode = 0;

void setup()
{
    Serial.begin(115200);
    pinMode(buttonPin, INPUT_PULLUP);
    servo.write(0);  // servo intial position
    servo.attach(servoPin);
}

void loop()
{
  static unsigned long timer = 0;
   unsigned long interval = 50;  // check switch 20 times per second
   if (millis() - timer >= interval)
   {
      timer = millis();
      // read the pushbutton input pin:
      buttonState = digitalRead(buttonPin);
      // compare the new buttonState to its previous state
      if (buttonState != lastButtonState)
      {
         if (buttonState == LOW)
         {
            // if the current state is LOW then the button
            // went from off to on:
            mode = !mode; // toggle the mode
            if(mode)
            {
               servo.write(90);
            }
            else
            {
               servo.write(0);
            }
         }
      }
      // save the current state as the last state,
      //for next time through the loop
      lastButtonState = buttonState;
   }
}

[wildbill]

This morning, I had no idea what a coal dumper was. Now I do; nonetheless, it would be nice to see a picture of what you're making.