Picking a Variable Resistor to Adust the Speed of E-Z Streets Vehicles

First off, a resistor is a poor choice.  If you want to have a consistent component, use one or more diodes.  For Streets vehicles, a 1: diode like the 1N400x (x is 1 thru 7) would be more than sufficient.  Since you're not likely to want to run in reverse, you don't need to consider bi-directional capability.  Each diode will drop the voltage around .6 - .7 volts to the motor.  Obviously, the diodes are installed in everything but the slowest vehicle.

I agree with GRJ that diodes might be a better choice.  As for budget, 1N400x diodes are about a penny a piece on eBay.  For example:

As GRJ says, this type of diode will drop motor voltage by about 0.6-0.7V.  Though if trying to fine-tune just a few percent, I wonder if this is too much drop.  There are diodes that drop less voltage - about 0.3V or so.  For example:

But there have been many threads decrying how even command control engines with digital speed control eventually reach bumper-to-bumper without some external traffic control.  

As to your comment about insulated track block power control, is this in reference to losing the 3rd rail for solid electrical contact with the (relatively) lightweight E-Z Streets vehicles?   Have you considered other block-occupancy sensing methods - current detection, infrared (IR), magnetic, etc.?  These would require a relay to kill power to the trailing block but should be modest in cost - maybe $5-10 - but of course would require fussing with track wiring/connections.

It seems to me that you will always have one car faster/slower than the others. Eventually, one will catch up to the others no matter how close you can get their speeds to match.

I would be looking for some other kind of control to keep the cars apart. It can be done but it's a lot of work. What you could do is sense a car on one section and alter the voltage to one or two sections behind the leader to slow down any trailing cars. Or as Stan suggested, just remove power so that the trailing cars would stop short of a collision.

John, Stan, Leo,

Thanks so much for your knowledge and input .

Thanks for the heads up on my poor choice of using resistors. I follow you (John and Stan) on the use of diodes and appreciate the inclusion of the nomenclature. I think that I would still have a problem after installing a diode in that I may slow a fast car down so much that it becomes the slow car. In the case where it wasn't slowed down enough, would a second #1 diode be installed (series or parallel?) ; or would a #2 be used?

Is there any kind of a trimmer device that is diode based that would allow fine tuning?

To your point Leo, I agree that there will still probably be a catch up but hopefully not as often. On my own layout it takes 3 - 4 trips to catch up; but on our community Christmas layout it takes 1 or 2 trips to catch up. What makes it worse is you have to nudge the kids out of the way to get to the EZ streets in the center of the layout. 

On my own layout I installed a dead track that requires the push of a button to supply the common. I picked up some EZ insulted rail that I could use and wire it in parallel with the button. The problem there is the slow cars get stopped as well as the fast cars.

Yes, you can combine diodes in series, mix or match, and their voltage drops add together.

The diode(s) would be placed between the bridge rectifier and the motor as shown in this photo hijacked from this thread.  

Orientation of the silver bands is important - be sure you know what this means if you choose this route.

I am not aware of any practical/economical method to fine-tune the voltage drop using the diode method.  That said, if you are presently re-adjusting position after only a few loops of operation, let's say you improve this to, say, 10 loops of operation.  Hmm.  For the effort, I strongly suggest looking at some method of controlling the track power to slow down or stop a vehicle that is tail-gating a slower vehicle.  Done right, you should never have to manually over-ride the operation.

As Leo says, you don't have to stop a tail-gater.  You can simply reduce the track-voltage (using diodes) in a short track section if a vehicle is occupying a track section in front of it.  This can all be "automatic" using some form of occupancy sensing and a relay to temporarily remove or lower the voltage In that short track section.  This means you won't have to modify the cars themselves.  Again, the cost would be modest - I'd say less than $10.

Personally, I'd bite the bullet and do block control.  For the trailing block, I like the idea of just lowering the voltage so the fast car slows down but doesn't stop.

John,

would the voltage controller board that you made for lighting work for fine tuning the voltage to motor?

Not on Streets, but I used slow down blocks on two blocks, (3/4 loops) before they merge into a shared single mainline(1/4 loop..one wall). The single mainline must be 100% clear of the mains exiting turnout as it is triggered to match or oppose, but change along with the anti-derail turnout at the mainline entrance.

 You still have to balance them just not as often; possibly many hours if you get it just right.

  The slow down block is very nice, but a stop block after them is still needed to insure proper operation in all circumstances. 

Exactly balancing the motors poses the exact same issue. It helps but actually just prolongs time between adjustments.

The stop abilty is the base needed to ensure a collision just plain can't happen. 

A 3-position slide switch and diodes gives three speeds.

3 pos. may work well enough if they are all dialed in close enough with other diodes that are not switched in or out. 

Moonman posted:

John,

would the voltage controller board that you made for lighting work for fine tuning the voltage to motor?

No, my lighting board is a constant current board and doesn't provide sufficient current to run these motorized units.

If unattended operation is the goal, then some type of blocking is going to be needed.  Unless the vehicles are running at the exact same speed, one vehicle will eventually catch up with the other.  If you have DCS and would consider Protosound trolleys instead of EZ street vehicles , than maybe some type of programmed station stops might work.  If attended operation is OK with DCS and Protosounds, you can always adjust speed to avoid collisions.  Here is an idea I'm working on, maybe some of this information would be helpful:  https://ogrforum.com/topic/taxi-scene.

Again, thanks for all the input. I think with all the information provided I will go with block control. About 35 years ago I had set up three blocks on a long loop that my friend wanted to run Budd cars on. We ran three sets and they would step around the layout. 

So I'll go with the suggestion  on the slow down rather than stop. A collision is not really a problem because if they catch up they just run one right behind the other. So a full stop is not needed, although if the stops were positioned in the right places it would look reasonable for a stop to discharge a passenger or deliver goods. So now I have to get busy and set it up and test it on my layout and then be ready to install it on the club layout in November. We set up the layout in the clubhouse gathering room; this will be the fifth year. We aren't allow to start until the first Monday in November and must have it ready for the first Sunday in December when we open with our pancake Breakfast and a visit from Santa. 

Steve, I like your taxi idea, I'd like to share that I had a dogbone streets on a previous layout. I never wired the wye. When the trolley came around the wye it mechanically moved the frog. On the return trip it would enter the wye on the same path it left. So the direction into the wye alternated back and forth. If you don't care which way it goes around the wye you can save yourself some work

A one stoplight town ?

I hadn't really thought about it, but the timer mech's resistor or maybe modern board version taken from an automated station could help with guesswork on which resistor to use if that route was chosen for some reason.

 My A. Flyer City Station uses a ¼"-⅜"-ish square x 1½"-ish long ceramic one. I think 10w at that size but forgot the ohms. I'll try to remember to see if I can read it.

  They get quite toasty though. I'd expect an overrated diode choice to be cooler. I use a diode drop with most of my other voltage drops.

  You may want to look at in-rush limters if you think any jackrabbit acceleration is going to be a possible issue.

A resistor is simply a bad choice for this kind of task.  Really, the block control is the only real solution for this that will be bulletproof.

I can't remember where I read this but there might be an issue using insulated-rail to detect block occupancy on E-Z streets.  The light weight of the cars and wheel-track dimensions are such that you want to always have fully powered outer rails.  The typical method of insulated-rail detection denies half of the available outer-rail contact points.  

Whether stopping or slowing the tail-gating vehicle, you need an occupancy detection method.  Shorling's taxi scene referenced in earlier post uses infrared (IR) detection...though not sure if chosen for reason cited.

stan2004 posted:

I can't remember where I read this but there might be an issue using insulated-rail to detect block occupancy on E-Z streets.  The light weight of the cars and wheel-track dimensions are such that you want to always have fully powered outer rails.  The typical method of insulated-rail detection denies half of the available outer-rail contact points.  

Whether stopping or slowing the tail-gating vehicle, you need an occupancy detection method.  Shorling's taxi scene referenced in earlier post uses infrared (IR) detection...though not sure if chosen for reason cited.

Stan, your comment relative to the EZ Streets insulated rail issue was on my post about the Taxi Scene you were helping on.  I agree this is would be an issue with EZ Streets.  Some type of drop out filter would be needed.  Maybe a drop out delay timer.  IMO the issue is an EZ Street vehicle weight issue.  The light vehicle weight contributes to the intermittent insulated rail.  If you put an engine on EZ Streets or a Trolley I think the insulated rail concept would work.

Adriatic posted:

I hadn't really thought about it, but the timer mech's resistor or maybe modern board version taken from an automated station could help with guesswork on which resistor to use if that route was chosen for some reason.

…

The classic automated station timer mechanism (e.g., #132) got me thinking about current sensing for block occupancy detection.

The resistor (nichrome wire) starved the engine of voltage to stop it - and heated up to trip the thermostatic switch to restart the engine after a time delay.  The point is temperature changes slowly in the resistor which "filters" out any short-term contact issues.  Not sure how to apply this to the matter at hand, but I figure this is the type of discussion that will eventually bubble a solution to the surface.  

As Shorling suggests, maybe a "delay timer" of some ilk might apply.   Many detection schemes (like IR) only detect occupancy at a point on the track.  The insulated-rail detects along the length of the insulated-rail section which can be arbitrarily long.  Hence point-detection methods often have some kind of delay-timer circuit which, in effect, increases the length over which occupancy is detected.

Ok so with infrared or a photoelectric cell  activation I would expect that I’m going to need a timer to keep the slow speed track active for more than an instant. 

Right.  I'm seeing a delay-timer in your future. 

A basic no-delay relay module (with screw-terminals, so no soldering) goes for about $1 on eBay (free shipping from Asia).  Depending on the required sophistication/features, a relay module with delay capability adds a few bucks...or less than $1 if you don't mind fussing at the component level (e.g., resistor, capacitors).  If you're not familiar, there are some photos of what I'm imagining on Shorling's thread linked above.

  The AF station used cams gear driven off the record player motor. The cam flexed a couple of leaf switch to time each make or break.

  The resistor value is a given, and works for me at about 5v with can motor MOW. The lights do not drop out but the motor stops.  Low voltage engines are harder to set. You must really set it by the drop voltage stopping the motor and hope it doesn't scream off on on full voltage.  I.e. a tad too many ohms for modern stuff, but a given value to work from.  

The diode has advantges as was pointed out.

How big is the SS ?  Three blocks, three triggers worth ? 

After using a combination of Diodes to get the speeds as close as you can. Fine tune by adding stick on wheel weights inside the slightly faster vehicle to slow it down. To do this you would have to test to find your slowest Vehicle and adjust all the others to this speed.

Before we got spoiled with command and control that was the way you would keep conventional trains running on the same track separated. You would adjust the speed by adding extra heavier cars to the faster train.