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I want to make a remote for Thomas Battery Powered Engine that will allow it to be turned on and off, but I don't even know where to start. I assume I'll need a receiver that can toggle power on and off to the motor in the engine and an external transmitter. Can I use the AA battery in the engine to power the receiver?

My hope was to be able to control multiple units via bluetooth from a smartphone.

What should I read/ask/buy to get started?

I'm not even sure this is on topic for this site.

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  • \$\begingroup\$ Some toy train sets use magnets in the tracks and reed relais in the engine to do simple toggling. They have a simple trigger switch to turn the engine on. Seen at a 80's Lego Duplo Train. This should be fairly easy to make, and have low power consumption. Think about a Flipflop or retriggerable Monoflop. \$\endgroup\$ – posipiet Feb 28 '11 at 5:55
  • \$\begingroup\$ They already make a remote controlled Thomas engine that's the same size as the standard Trackmasters trains. Perhaps someone has already posted the disassembly online and you can glean some info from it? I have one at home and if I can find it, I'll try to snap pictures for you. \$\endgroup\$ – Dave Feb 28 '11 at 15:22
  • \$\begingroup\$ @Dave I'm really attached to the wooden tracks, but that's just me and a little superfluous to the solution. \$\endgroup\$ – antony.trupe Feb 28 '11 at 15:25
  • \$\begingroup\$ @posipiet I hadn't considered that. \$\endgroup\$ – antony.trupe Feb 28 '11 at 15:26
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I can't help much on the remote part. You'll most likely want to use radio, but I can't provide anything more specific than that.

I also can't give good advice right now, but that's because of the low amount of information in the question.

So first step would be to carefully disassemble the engine and post some photos of the circuits.

You'll most likely find one or even two motors inside (they do mention 4x4 drive) and see how they are controlled. Next step would be to decide what you are going to do. The description is a bit vague but I think that they mention multiple buttons on the unit. You'll have to decide if you want to completely switch to remote control, just have remote on-off control and local controls or have full remote and local control.

Basically, if you want remote on/off control, you could accomplish that in two ways: place the extra switch at engine's main power connector or place extra switch on engine's motor power connector. It could be easier to just switch completely to remote control, but again that depends on internal wiring and available volume. I'd have to think a bit for full remote and local control.

As for the switch itself, to me a MOSFET in TO-92 package looks like a good idea. If you can afford it, get one of the more expensive ones. They'll most likely be around 1€, but will have much lower internal resistance than cheaper ones which means that they'll consume less power for themselves.

Also for the radio power supply could be a problem. Common voltage levels for hobby electronics are 3.3 V and 5 V. On the other hand, AA battery provides between 1.6 V and 0.8 V, so you may have to make or get prefabricated converter. Of course, this will negatively affect power consumption.

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You might want something like this DC Toggle switch, but to be sure, we'd need more information on how this train works

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Are you ok with the remote working in Line of sight ? If yes you can use IR to control it. I think there will not be any circuit that drives motor in them and will be rigged directly to the battery. In case it produces some kinda music then there might be a circuit for it in parallel. But you can get this working pretty easily even if it does have a circuit but for any result you will have to open it and see inside :D

With a small circuit you should be able toggle the power to the motor. I would first connect my motors directly to the battery and see how much current it draws and then decide on using either some motor controller or MOSFET for this JOB and the use a simple IR receiver and few electronics component to rig up a small circuit. This should be fairly easy. For having circuit level help you need to post the details as of how much motor it uses (my guess is 1) and how many batteries it is powered with.

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