# Shuttle (auto reverse) device experiences



## perego (Feb 1, 2017)

Looking for comments on shuttle devices.
I currently use the type with diodes across track gaps which slams the trolley to a stop, although I'm about to try an idea I found of putting additional track sections before the diode sections with resistors spanning gaps to knock the voltage down before finally stopping after passing the diodes. Maybe better but not as good as other devices I'm looking at.
A DCC one looks interesting because the slow down is CV controlled and I could "exercise" other locos I have that are DCC. Track gaps are used so I figure to accommodate varying end zone lengths one could have multiple gaps with switches to decide which is the functioning gap. One downside is if powered off in an end zone the trolley/train may start up next time going the wrong way. Not a big deal if I put a failsafe power off switch on the track ends.
The main difference I see in two different DC devices I'm looking at that both will slow the trolley to a stop, is that one uses track gaps and the other uses sensors (reed switch, IR, etc.).
Moving sensors seems like a handy way to accommodate varying train lengths and the "trip" point is known whereas with the gap controlled units I'm not sure what will happen with a lighted caboose.
I would like the trolley lights to stay on while paused at the end zones and to be at the same brightness when moving at any speed. Have more ideas but will leave it at this hoping to hear about experiences.
Thanks, Bob


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## dbodnar (Jan 2, 2008)

*Arduino Based Auto-Reverse*

Funny you should ask, Bob - I was unhappy with commercial offerings from the time I started with G-scale a dozen or more years ago so I designed my own. It works very well and automatically decelerates at each end of the point-to-point without adding sensors as the deceleration point is based on time.

A few weeks ago I decided that it was time that I revisit my original design (which was based on a PIC microcontroller) and build an Arduino based auto-reverse controller.

I have several prototypes working very well and hope to finish up this project in the next week or three.

You are welcome to see where the project is now and revisit the page below to see how it is progressing. Stay tuned!

dave

http://www.trainelectronics.com/Arduino/BARC/


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## Dan Pierce (Jan 2, 2008)

Resistors really just limit current, different engines will give different results when using resistors. Diodes will give a voltage drop and all engines will work somewhat the same!!
Silicon diodes will drop .7 volts each.

I only use 1 engine so the 4 ohm resistor works for me with my toytrain cow single motor engine with 8 cars on level track and 2 R1 90 degree corners..


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## Totalwrecker (Feb 26, 2009)

What about an on board device to control the trolley independent of your other trains?

http://www.gscalegraphics.net/store/p14/Enhanced_Critter_Control.html

dos centavos

John


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## Greg Elmassian (Jan 3, 2008)

Nice idea dave, do you have a rough estimate on the parts costs?

Greg


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## dbodnar (Jan 2, 2008)

Greg Elmassian said:


> Nice idea dave, do you have a rough estimate on the parts costs?
> 
> Greg


Greg - costs are much less than any commercial unit is likely to cost. 

Arduino Pro Mini - $5.00 or less
H-Bridge - $5.00 or less (the red one I am using is only good for 15 volts but there are similarly priced ones that are good to 20 or more) 
Rotary Encoder - $2.00 or less
0.9" OLED display - $8.00 or less
Misc parts (wire, etc) - $5.00 or less
Arduino code - free

TOTAL $25 or much less if you order carefully - a good bit more if you shop Amazon prime!

dave


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## Greg Elmassian (Jan 3, 2008)

The display looks like it has a serial interface, is that so?

Greg


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## perego (Feb 1, 2017)

Interesting ideas, thanks.

Dave - I've been looking for an arduino project so this looks interesting even though it doesn't address my desire to have consistent light intensity (without leds and a VR) and because you employ gaps with diodes I'm assuming no power in the end zones. Speaking of the diodes why would the polarity be different for HO?

Dan - if I'm envisioning your suggestion of using diodes instead of resistors for the "slow down" zone, I don't see how this can work because those diodes to reduce the voltage would need to be placed in the opposite polarity of the "end zone" diodes and would hence stop the trolley when it reverses. May need to include a diagram.

The critter control is interesting but impracticable because my new point to point track will be high. But the control of stops is handy given the reed switch is in the trolley/train hence making it easy to move the magnet in the tracks - if I understand how the device works.


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## perego (Feb 1, 2017)

Dan - perhaps this is what you had in mind for the slow down zone diodes: the sets of diodes in parallel solve the reversing issue and add a bonus of allowing a startup speed.


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## dbodnar (Jan 2, 2008)

Greg Elmassian said:


> The display looks like it has a serial interface, is that so?
> 
> Greg


Not serial, Greg, but I2C - that interface uses a clock and a data line to send info to the device - works well and can be faster than serial.

Here is a link to the display I use - note that the ad says 128x64 - in reality it is 128x 32 - in any event it allows about 20 characters per line and 4 lines at the font size that I am using.

http://www.ebay.com/sch/i.html?_fro...I2C+IIC+SPI+Serial+128X64+White+OLED&_sacat=0 

dave


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## dbodnar (Jan 2, 2008)

Bob - you are correct that there is no power available at the ends of the point-to-point. There are ways to get around this such as using super caps that charge during the active period and keep the lights on for a time at each end.
As to diodes there is a detailed discussion of how to wire them up to slow trains on my web page here:
http://www.trainelectronics.com/art...ller/Part_3-diodes_speed_control/part_III.htm










dave


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## Dan Pierce (Jan 2, 2008)

I would make the diodes under sw2 with a diode bridge and sw4 2 diode bridges.


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## Greg Elmassian (Jan 3, 2008)

Acutally the circuit on the right is most efficient when you start having more drops and it's easier to wire up.


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## perego (Feb 1, 2017)

Thanks for the additional diode info. Picking some up tomorrow to experiment with.
For the new point to point I'm making I'm leaning towards the TamValley DCC device. Someone local is getting one shortly so hopefully some of my questions about it will get answered.
Having been a programmer before I retired I'll have to play with the arduino idea just for fun. I also just found out about the open source DCC++ technology.
Ha, this new track is getting expensive - already bought a railbus and another trolley this week.
And, I'm now thinking about how to use some the ideas to make my LGB cable car slow to a stop.


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## Greg Elmassian (Jan 3, 2008)

many dcc decoders, especially massoth, zimo, esu, will slow to a stop when hitting dc and some other options. I don't know all of them, but sounds like you are going battery so you won't have these easy to use options, but there might be some options.

Greg


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## dbodnar (Jan 2, 2008)

perego said:


> For the new point to point I'm making I'm leaning towards the TamValley DCC device. .


Bob - if you decide to go the Tam Valley route I have a new unit on the shelf that was just used for testing - I'll make you a deal on it!

dave


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## Dan Pierce (Jan 2, 2008)

I Greg's diagram the diodes in the middle can have SPST switches to short some diodes out to change the voltage drop.


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## perego (Feb 1, 2017)

Thanks Dave, sent you a message.


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## perego (Feb 1, 2017)

Even though I have a DCC unit on the way, I picked up some diodes to experiment with. For the speed I was running a trolley at, 3 diodes cut the speed about in half. I suspect this might help save the gears but I think it would take 3 of 4 slow down zones with increasing number of diodes to look fairly realistic.
Add to this changing lighting to LEDs with a voltage regulator to maintain consistent intensity, and a keep alive for the end zone (or battery lights), and the DCC solution is looking even better.
Off topic but while at the electronics store (Vetco) I picked up an inexpensive voltage regulator that tested nicely for powering LEDs. Even though it is analog for a few LEDs it generated no heat without a heat sync.
Good to go, thanks for all the comments. Will post anything of interest after I experiment with the DCC unit.


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## Dan Pierce (Jan 2, 2008)

Due to current and voltage being able to change, a resistor gives smoother operation as there is no voltage jumping between values.
I would try Greg's diode bridge and place a resistor of 3 ohms ( and use 2 watts or more) between the + and - terminals.


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## perego (Feb 1, 2017)

I was going to try this Dan but the electronics store was completely out of low ohm resistors. Would not have thought I'd ever say this but I miss my local radio shack!


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## Dan Pierce (Jan 2, 2008)

Just remember that 3 10 ohm resistors at 1 watt in parallel will give 3.33 ohms at 3 watts!!


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## perego (Feb 1, 2017)

Tested the TamValley shuttle, thanks Dave.
It works well as advertised with one nuance some might care about.
The stopping point can vary, in my test up to 6 inches. I found out this is because the unit works for any loco placed on the track by cycling through loco numbers 1 through 99 when issuing the stop and start commands. So, where the sensing of the gap crossing occurs relative to where the looping through the loco numbers is, results in variable stopping points. 
As advertised, sound commands cannot be issued, but if the decoder has the sound on, you will get sound, just can't turn it off or activate the whistle etc. 
Not sure what the minimum draw is for the sensing in the end or middle zones, but when I backed a caboose with only 3 small lights, it was enough to trigger the unit.
While testing I had a knuckle coupler jiggle loose - no telling how the unit might get confused with a loose lighted car.
I had one "malfunction" when after stopping, the loco went the wrong way. I couldn't repeat this and may have violated the 5 second end zone to end zone rule. I did locate one other user who had a similar failure.
But, for a number of reasons I think the prudent installation should include either a failsafe switch on the ends, or an isolated track section on each end, although this will severely extend the run if shuttling a train with cars.
The decoder set acceleration/deceleration works nicely, and of course light intensity doesn't vary, which were the two main things I was looking for.
I hope TamValley comes out with a subsequent unit that allows for specified loco numbers, or even something as simple as an option for a known loco number, so the variance in stopping points can be eliminated. I did find out that there is another variable, that being it needs to see uninterrupted current in the end/middle zones for 1/10 a second to trigger.
All in all, a nice shuttle unit.


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