What type of electrical switch/sensor do I need?

Question

It's hard to explain but basically I have a rollercoaster model. I want it to run like a real rollercoaster where a train will stay in the station while the other train moves up the track. I need a switch that I can place on the track and once the 1st rollercoaster hits this switch/sensor the motor on the station will turn on and the 2nd rollercoaster will start to go up the lift. You can see rollercoaster I am working with at www.coasterdynamix.com

Answer 1

I'm not sure I understand the question exactly. Just about any type of sensor or switch would work. You could use a physical switch that trips using a physical contact as the car goes past, you could use an IR detecting diode with an interrupt beam (i.e. "electric Eye" beam), a magnetic reed switch and a magnet on the car... all sorts of things.

Can you be more specific about what you are after?

TV

EDIT - More info after the question asker posted additional info....

Oh, Ok. So what you want is not a control system for the lift ramp motor but a gating system to stop the second car from reaching the lift ramp (which I assume is continually running?) until the first car gets to a certain point along the track. Is this correct?

Assuming it is, there are several ways that this could be done and the best way depends heavily on what your level of electronic expertise is, how much you want to spend, and how much trouble you are willing to go to.

This is how I'd do it (bear in mind my background is in electronic engineering)...

1) Place a normally open (NO) reed switch (sw1) about 1/2 way around the track. This would be triggered by the already moving car (car1) and would send the "open gate" command to the latch circuit (see below).

2) Place another NO reed switch (sw2) about 20mm before the bottom of the lift ramp. This will send the "close gate" signal to the control circuit after the waiting car (car2) has gone through the gate. The gate will be some distance before sw2 (it's up to you how far and is partially dependent on how long the cars are.

3) Attach the magnet part of sw1 and sw2 to the cars. Mount them as close to the end of the cars as possible.

4) Connect sw1 and sw2 to the inputs of a simple latch circuit (see below) and a small relay or power transistor to the output. This will be used to drive an actuator (probably a solenoid) connected to a plastic coffee stirrer or something similar which will be positioned in such a way as to block the track in the closed position and clear the track in the open position.

The latch circuit is necessary because sw1 and sw2 only stay closed for a moment as the magnet on the car goes past. Without it the gate would just open and quickly close again. The latch circuit detects the short pulse from the switch and locks it there until it receives another signal.

A latch circuit is very simple and, apart from the actuator and the switches themselves, consists of just 3 components (5 if you want to add an indicator LED) but I can't draw it for you here so you'll need to find a circuit diagram somewhere or locate some kind soul who will build you one in your area.

Alternatively, you could take a crack at it yourself (it runs off batteries so is safe, you won't zap yourself if you make a mistake). The circuit is known as a bistable latching switch circuit and is built around a CMOS 4013 Dual D type flip flop. That probably doesn't mean much to you but it may help you track down a circuit diagram and get you started.

If you do want to have a go yourself, I recommend getting a book called "The CMOS Cookbook" (Author: Dan Lancaster, Published by: Newnes, ISBN: 0-7506-9943-4) it will give you all the info you need for little projects like this.

Alternatively, you can find this exact circuit under Section 46 ("Latch Circuits") in a book called "Encyclopedia of Electronic Circuits" (Authors - Rudolf F. Graf & Wiliam Sheets, Published by McGraw-Hil, ISBN: 0-07-015116-4). If you buy it, borrow it from the library or can somehow get access to an electronic copy on the web, you'll see the circuit you need for this.

Well, I think that about covers it. Sorry I went on for so long.

Hope this helps.

TV

Answer 2

There are two ideas that come to mind:

The first is called a reed switch.  Mount a little magnet on each train, and a reed switch along the track.  When the magnet gets close enough to the switch, the switch will trip for as long as the magnet remains close enough.  A simple circuit could latch as a result, and unlatch when the magnet passes a second switch.

Another option is a photo-interrupter.  Basically, a beam of light would shine from one side of the track to the other, and  would send a pulse when interrupted by the train.  A little more circuitry would be involved, but at least it wouldn't change the weight or mass of the train.

Answer 3

I'm not sure of the electrical specs - the site just shows pictures.  I would think that a magnetic reed switch might work with some other components.  Attach a small magnet to the bottom of the lead car, and a reed switch at the point where detection is needed.  The switch would need to interface with the rest of the roller coaster mechanism...

Answer 4

I would use a "reed" style switch or a light beam / photo sensor. A light beam across the track will trigger a relay or transistor circuit, thus sending the car off on its way. The switch  will work the same way.

Or assuming the cars are "coasting" into the shoot by themselves without power. Have a switch at the front of the shoot. This switch can be used to hold the car in position so it doesn't roll out. Have another switch or light beam at the end, and when the car comes in, the beam is broken and it releases the car in the front to go out on the track or coaster. If you need more details pls dont hesitate to email me. I can get more info from you on how exactly you want it to work and I can get you a design.