Train Plan

[Denny]

I started disassembling the Perego train that my daughter gave me, getting ready to modify and paint it. I plan to use the EZ Light Linker and LOR DC board to control it. Based on advice from others, I plan to use the two existing 6 volt motors for power and use a 12 volt deep cycle battery for accessories. Originally, I was thinking of just using one of Wirekat’s” MR 16 bulbs for a headlight, but while working on the train, I thought I might make some other changes as well. Looking for advice and comments on the following.

1. I am thinking about building a snow machine that will fit inside the locomotive using a 12 volt automobile defroster blower and 12 volt pump for the snow fluid. The snow will come from the smoke stack. I would also install a blue MR16 inside the stack, pointing upwards, to give some illumination to the snow. The locomotive is hollow as the motors, 6 volt motor battery, and running gear are located in the train tender.

2. The train also has another car that attaches behind the tender which could be used to hold the EZ light linker and LOR DC board.



3. To hold the 12 volt battery, I was thinking about getting a small ice chest to convert into a third car.

4. Since I have everything apart to clean and paint it, I would like to drill some holes so I can install some LED lights to decorate the train. The LEDs that I am thinking of using are the ones that were used for demonstration purposes and placed in the cases of LED lights in the stores. Generally, there are six LED lights connected to two AA penlight batteries (3 volts). You would push a button and the lights would light. I got these when I bought the cases of LEDs at Home Depot after Christmas. I would like to be able to control them using the LOR DC board, but the strings only run on 3 volts. I will be using half the LOR DC Board at 6 volts for the train motors and the other half at 12 volts for the MR16s and the snow machine blower and pump. Somewhere in the back of my brain, I remember reading that for model railroading I could reduce voltage by installing a series of diodes. Diodes were recommended since the use of resistors would increase amperage. Would this work to drop the voltage to the LEDs down to three volts? Would I still be able to do fades with the LEDs using the DC board? Any other ideas out there?

[VetteNut72]

Hi Denny,

I always liked the idea of a train but I don't have the yard for it. Looks like you have some great ideas and it will be nice to see what you come up with.

I am going to try and make it to the ACL July meeting, just have to see what the GFs plan is so she can take me up there. I try not to drive much anymore and my car has been broken (well, slow restoration) for over 5 years now. It will be nice to meet some of the Arizona Christmas Lights guys.

Craig

[Steven]

Denny wrote:

The LEDs that I am thinking of using are the ones that were used for demonstration purposes and placed in the cases of LED lights in the stores. Generally, there are six LED lights connected to two AA penlight batteries (3 volts). I would like to be able to control them using the LOR DC board, but the strings only run on 3 volts.

LEDs run on 2-3 volts. If you can disassemble the demo LED lights and connect 4 of them in series, then you could probably power them from 12 volts. You'll have to experiment with the LOR DC board because the voltage of the 12v battery varies from 13.5 to 12 volts (approximately) depending on how much charge it has, and the LOR DC board will drop that voltage by a quarter volt or so.

Start with a 50Ω resistor in series and see how bright they are. Reduce that by steps until you get the desired brightness, or until the LEDs stop working if you don't mind doing destructive testing. (Destructive for the LEDs; you won't hurt the LOR DC board.)

If you can't get 4 in series to get bright enough, then reduce it to 3. Depending on the color, this will be 8-9 volts, so your resistor will need to drop 3 volts. I don't know how much current these LEDs take, but if we assume 60mA, then you will need a 50Ω resistor.

Denny wrote:

Somewhere in the back of my brain, I remember reading that for model railroading I could reduce voltage by installing a series of diodes. Diodes were recommended since the use of resistors would increase amperage. Would this work to drop the voltage to the LEDs down to three volts? Would I still be able to do fades with the LEDs using the DC board? Any other ideas out there?

A diode will reduce the voltage by about .7 volts, but in this case there is absolutely no reason to use diodes.

[-klb-]

Steven wrote:

Denny wrote:

Somewhere in the back of my brain, I remember reading that for model railroading I could reduce voltage by installing a series of diodes. Diodes were recommended since the use of resistors would increase amperage. Would this work to drop the voltage to the LEDs down to three volts? Would I still be able to do fades with the LEDs using the DC board? Any other ideas out there?

A diode will reduce the voltage by about .7 volts, but in this case there is absolutely no reason to use diodes.

And the diodes exhibit the same non linear voltage response as the LED's. You want the resistance there to make the voltage to current response more linear. Also, the methodology Steven describes is a good practical approach to get to where you want to be. My $0.02 is that you might want to start with a higher resistance, on the order of 150 ohms, just in case the brand of LED's you have are only 20mA.

If you are looking to use them individually, instead of in series, on 12V, you would want to drop about 9V through the resistor. For 20mA, a half watt, 450 ohm resistor would work well. For 60mA, 150 ohms should be on target, but you need a 1 watt resistor.

Or from 6 volts, for individual LED's, we are back to 150 ohm quarter watt resistors for 20mA, and 50 ohm, half watt resistors for 60mA

In any case, these should dim quite well on the DC card..

- Kevin

[-klb-]

You say there are two 6 volt motors? A couple different questions come to mind.

1) Are they both identical drive motors? Are they currently wired in parallel? If they are identical 6V motors driving the mechanism with identical gearing, and they don't share a common mechanical ground, you should be able to wire them up series to run on 12 volts, and only incur the switching losses of a single channel instead of two.

2) do you have some indication of the current draw on those motors? If it is small enough, you could probably handle it with the DC card and a good heat sink. One other option would be to use the LOR channel to drive a separate transistor that handles the motor current, allowing the heat sink to be remote from the LOR card and to move from the MOSFET output stage that works well for low current, to a BJT output stage where losses are more linear with current. Or you could use the LOR channel to drive a relay that switches the motor power. Each of them have their advantages, and issues.

- Kevin

[Denny]

An update on the demo leds that I am using. First, I made an error in my original post, they run on 3 AA batteries, not two, so it is 4.5 volts. Next, I took one of the strings apart. There are 6 leds on each demo string and they are wired in parallel, not series. :shock: So, each led is getting 4.5 volts. Some leds (red, orange, yellow) have a resistor soldered to it and two wires are soldered to the resistor (one wire from the previous led and one going to the next led). The blue and green leds have no resistor. The other leg of the led also has two wires soldered to it, one from the previous and one going to the next led. Besides the resistors soldered on each led, there is a single resistor soldered to the wire coming from the negative battery terminal. So, looks like I need to have at least a 4.5 volt supply going to the DC board. I am puzzled though, what is the purpose of the single resistor in the negative battery line?

As for the two motors, it looks like I can easily wire them in series and connect them to a 12 volt battery to get the 6 volts into each motor. But thought I read in an earlier thread that I needed to keep the motor circuit separate from any that controlled lights due to surges. Is this a problem?

[Denny]

-klb- wrote:

You say there are two 6 volt motors? A couple different questions come to mind.

1) Are they both identical drive motors? Are they currently wired in parallel? If they are identical 6V motors driving the mechanism with identical gearing, and they don't share a common mechanical ground, you should be able to wire them up series to run on 12 volts, and only incur the switching losses of a single channel instead of two.

2) do you have some indication of the current draw on those motors? If it is small enough, you could probably handle it with the DC card and a good heat sink. One other option would be to use the LOR channel to drive a separate transistor that handles the motor current, allowing the heat sink to be remote from the LOR card and to move from the MOSFET output stage that works well for low current, to a BJT output stage where losses are more linear with current. Or you could use the LOR channel to drive a relay that switches the motor power. Each of them have their advantages, and issues.

- Kevin

These are identical motors and gear boxes. There is a separate motor for each drive wheel -- again, a surprise to me :shock: The battery that came with the train is "caput" so I can't answer anything about the current draw yet. The motors are wired in parallel; so I could rewire them in series and run off of a 12 volt battery. I understand the relay part of your comment # 2, but have no idea how to approach the first part of your suggestion with MOSFET, etc. I know only enough about electronics to either A). Read a simple schematic . Really hurt myself by letting all the smoke out through my hair (that's why I am getting so bald now)!

[-klb-]

The relay should always be a solid fallback plan, and you should be able to find a relay to handle any current you need, but it will always be an on/off only situation.

Once you get some current readings, I can comment on any opportunities to control the motors without the relay, to allow speed control.

Also, at some level, it looks like it might make sense to run both the motors and LED's off of a 6V battery, but then you still need a 12V source for the DC card logic..

The advantage to having separate batteries for the LED's and motors mostly has to do with avoiding the fluctuations in brightness as the motor switches on and off, and the battery voltage changes.

It sounds like you could avoid most of this using an adjustable voltage regulator set at 4.5V to supply the side of the card feeding the LED's, then as long as the battery voltage does not dip below 4.5V, there should be no impact..

Or the LED's could still be run individually on 6 or 12 volts, you just need suitably sized resistors in series...

- Kevin