[Question] 9V Electrical Specifications

[Rail Co]

Hello all, it's been awhile since I have posted anything, sorry for that.

Anyway, I am away for awhile from my 9V trains and they are in a box somewhere (moving is a pain). However, I am trying to develop a motor controller PCB for my personal use and it will have 4 train signal ports to act like the 12V system did and stop the train when a button is pushed. However, because I don't have access to my collection right now I am wondering if you all could help me or point me to a topic I may have missed.

I can't remember how the 9V system provides power to the motor. Does anyone know these specs?

1). Does the motor run off of a DC voltage or AC Voltage source. I know the wall plug is AC but I can't remember if that is rectified and is changed to a DC output.

2). Does 1 rail carry 9V and the other rail carry 0v/Ground. Or is it that one rail runs on +9V and the other runs on -9V.

3). Has anyone done this type of train signal (like the 12v system did where 1 rail is cut off and the switch basically closes/opens the circuit) with an Arduino or other means and give me suggestions on what they did, if they wont to share their secrets of course.

Thanks to anyone and everyone who can help!

-RailCo

[Andy Glascott]

I can't answer your first 2 questions, but I have done 3, using a standard 12v signal set up. I think I posted a thread about it but haven't found it, if I do, I'll link to it, but here's what I did. 

I use the 12v signal switch to operate it all and run a standard 12v wire to the signal light brick. I then run a 12v wire from the switch to where the isolation mechanism needs to be. I've taken one of the 2x2 plates off one end of a short 9v wire (may or may not be this exact one) and replaced it with a 12v plug to create an adaptor between the two systems and connected the other end to a standard 9v track contacts wire. 

To create the section of track that is cut off from the power supply I simply insert a small piece of paper between 2 sections of track and repeat a few track pieces later. The 9v contacts wire is then attached so that the 2 contacts are on the same side of the track but either side of one of the pieces of paper. I have both 12v and 9v loops on my layout, so power the switch unit from a 12v transformer, but that only powers the light. The 9v track current comes from a 9v controller and runs through the switch completely separate to the 12v supply so when the switch is red the 12v lights the light and the 9v is cut, when it's green both are open. I'm guessing, as my electronics knowledge is limited, that if you just use a 12v switch to cut the power off it wouldn't need a power supply of its own. 

Overall, it works wonderfully, just takes a little bit of adjusting to get the pieces of paper in the right places to stop a train where you want it to stop. 

[zephyr1934]

3 hours ago, Andy Glascott said:

To create the section of track that is cut off from the power supply I simply insert a small piece of paper between 2 sections of track and repeat a few track pieces later.

I've used a small piece of folded over packing tape. For the power you could make your own switches and connectors for a lot cheaper than any pure lego solution, but pole reversers will do the trick. It might be cheaper to use PF pole reversers and the PF to 9v connection instead of the 9v pole reversers.

[Brickthus]

1) Here's the circuit diagram of 9V train controller:

The diodes top left rectify the 7V AC input and the capacitor smooths the unregulated power.  The LM317 regulates to 9V DC.

2) Rails carry 9V and 0V but a partial short circuit between two opposite-position controllers would create 18V across the un-shorted connections.

3) No, but I would try to follow either standard LEGO circuits or model railway book circuits, which may specify keeping signals isolated from track etc.

Mark

[Rail Co]

Thank you all for your replies.

@Andy Glascott I love the idea of using the original Lego 12v parts. It would be nice to be able to do. However, I don't think I have the funds to purchase those parts. Where as LEDs can be bought for pennies and a spool of wire for a few bucks. If I had the funds to purchase those original signals I would definitely go that route.

@zephyr1934 I am sure there are quite a few different ways to isolate one rail section. I will probably be doing this all with non-Lego parts. Not only for cost reasons but I plan on doing this all on a single Arduino shield if possible. Then just have wires running to the track and LED train signals. This gives me more options when designing the shield and I can make the feature I want all in one small package, if that makes sense.

@Brickthus Thank you so much for the regulator circuit diagram! This is a huge help to visually see what is going on inside. I wanted to make sure that the train ran on DC not AC which your explanation confirms. I am glad that it runs on one rail at 9V and one at 0V that makes life easier.

Thank you all for your help and suggestions!

-RailCo