# Would You Like to Give Your Engines the Ability to Ignore Current Reversals?



## toddalin (Jan 4, 2008)

With all the discussion on DCC and reverse loops in automated operation, I figured the primary advantage of DCC is the ability to have trains out on the mainline that don't reverse direction when the track current flips. (I'm assuming that with their sophistication they can be programmed to do this.)

But what if we could give this same ability to our "analog" engines..., for


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## DKRickman (Mar 25, 2008)

Sounds like the old Lionel E-unit reverser. Personally, I never cared for it when I was trying to operate, though it works just fine for just watching trains go around in circles. I'm a bit puzzled as to why you'd want to do this, though. What's wrong with reversing the polarity to reverse direction? You'll still have to do something about any reverse sections, since they will still cause short circuits even if the locomotive doesn't care what the polarity is. And if the goal is to make the engine always run in one direction, just put a bridge rectifier and a DPDT switch on the locomotive. You'll have to touch the model to reverse it, but I'm guessing you don't want to reverse very often anyway. And if you want, a second DPDT could be installed to bypass the bridge rectifier for normal operation as well. 

I would point out that the primary advantage of DCC is not being independent of track polarity, but rather being able to control multiple locomotives independent of their locations on the layout.


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## chuck n (Jan 2, 2008)

45 years or so ago I was building an HOn3 layout. I didn't know the name of the various layout designs, but I came up with a folded dog bone with one end of over the other. It looked neat. Sometime during the building I woke up in the middle of the night and realized that I had created two dead shorts. I was able to use two DSDT switches and run the layout. It required manual control and attention. Since then I have avoided return loops on all my railroads. In the long run it is a lot easier and simpler to run a parallel track back in the opposite direction. Yes it can be done with electronics, but I like to keep things simple. 


Chuck


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## Greg Elmassian (Jan 3, 2008)

Cool idea Todd. This feature has been in the QSI products for a long time, when they are in DC mode. The reversals are used to ring the bell, blow horn/whistle, and sequences of reversals can control 30 other functions. 

You might check to see if this is patented though... QSI is not like MTH, i.e. "sue happy" but would not hurt to check. 

Greg


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## Dwight Ennis (Jan 2, 2008)

You might check to see if this is patented thoughSo long as he designs his own circuit, I don't think there's a problem. One can't patent an idea - only its implementation. 

I found that out when, in the early 90's, I wrote a TSR that implemented features on a new joystick specifically aimed at air combat flight sims. This stick was modeled on an F4 joystick and was the first stick ever to have the "****** hat" (normally used then to trim the jet). As the flight sims of the day had no trim controls, the hat was useless. My TSR made it work. I was the first person ever to use the ****** hat to control views - look up, look left, look right, look behind, etc. It gave a real advantage during game play as one never needed to take their eyes off their opponent (off the screen) to look for the appropriate key to change views... as they say, "lose sight, lose the fight." 

It wasn't long (a year or two) before other manufacturers started marketing their own high end joysticks, and not long after that game makers started using the various hats of the various sticks for view control. While I'd patented my software, it was worthless here because no one had actually duplicated my code - they only "stole" my idea. hehehe The original joystick maker also couldn't sue because no one had actually duplicated their stick... only used the idea to come up with their own. They actually did sue another manufacturer - and lost.


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## Garratt (Sep 15, 2012)

Sounds like a good idea to me. Perfectly logical if you don't really want DCC.
I doubt anyone could sue for designing a circuit that automatically reverses polarity.
A patent doesn't necessarily give someone exclusive rights and may mean very little. Just something for sniveling lawyers to wave around. 
I've had IP lawyers harass me on the phone in evenings because they didn't have a leg to stand on. I just tell them to FO! They usually do. 

Andrew


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## toddalin (Jan 4, 2008)

Posted By DKRickman on 18 May 2013 05:03 PM 
Sounds like the old Lionel E-unit reverser. Personally, I never cared for it when I was trying to operate, though it works just fine for just watching trains go around in circles. I'm a bit puzzled as to why you'd want to do this, though. What's wrong with reversing the polarity to reverse direction? You'll still have to do something about any reverse sections, since they will still cause short circuits even if the locomotive doesn't care what the polarity is. And if the goal is to make the engine always run in one direction, just put a bridge rectifier and a DPDT switch on the locomotive. You'll have to touch the model to reverse it, but I'm guessing you don't want to reverse very often anyway. And if you want, a second DPDT could be installed to bypass the bridge rectifier for normal operation as well. 

I would point out that the primary advantage of DCC is not being independent of track polarity, but rather being able to control multiple locomotives independent of their locations on the layout. 

Not really like the Lionel I had. On those the train would change direction every time you dumped the thottle. So if you stopped, to go forward you had to go through reverse first, even if just to flip the relay.

This is not like that. When you dump the throttle you can go forward, if the current is still set to go forward, or backwards if you reversed the throttle, after the train stopped.

Also you miss the point. This is not to control the polarity of the line and that is still accomplished in any of the old fashion ways.

But what happens if two trains are on the mainline, both headed toward the loop, one in front of the other? When the first train passes through the loop and is now headed back toward the other train (that will take a sideing before they collide), the current to the mainline reverses in traditional fashion. So that train that was still out on the mainline that had yet to reach the loop reverses and is now heading backward, with both trains still headed in the same direction.

This would alleviate that situation and the train that was still out on the mainline will continue in the direction that it was heading (swimming against the current, so to speak) and take the siding before the inevible collision.


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## general1861 (Jan 22, 2010)

I'm interested Todd... Travis


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## Del Tapparo (Jan 4, 2008)

What's a TSR? What's an IP Lawyer?
(My trains don't care about reverse loops)


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## Greg Elmassian (Jan 3, 2008)

Terminate and Stay Resident.... Dos was not multitasking, so a program would run, then terminate, and be swapped out of memory for the next program. 

Terminate and Stay Resident means you could sort of have 2 programs running at one time, the TSR could basically run and share resources with another program. 

Intellectual Property lawyer. 

Never underestimate the patent office to grant ridiculous rights... MTH basically had BEMF on trains patented and held other US manufacturers at bay for a number of years... read up on it. 

Greg


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## toddalin (Jan 4, 2008)

Posted By general1861 on 18 May 2013 07:57 PM 
I'm interested Todd... Travis 

OK, I'll write up a synopsis and put it online and if this sounds like something someone wants to build, we can get into more detail and if there is still interest, I'll work up a schematic. Give me a day or two as we have an OCGRS club meeting tomorrow.


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## Garratt (Sep 15, 2012)

OP: "If this is of interest as a construction project for someone, I can go into the details." 
An individual is not bound by patent laws when building something for their own non commercial usage therefore any reference to patents is irrelevant. 
Even so, the loss to the company protecting their right would only be the amount they would have lost by the person not purchasing it from them.


I can see merit in the idea. Once the loco is underway, the track supply if suddenly reversed as when going over a returning track break just lets the loco continue in the current direction. Double lashed locomotives would just trip their circuit within, each in turn as they cross the break. 

Andrew


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## astrayelmgod (Jan 2, 2008)

I see you guys haven't been keeping up with the latest in patent "innovations". To pick one notorious example, Amazon has a patent on the concept of buying something with a single click. Not the process, not the implementation, but the concept itself.


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## toddalin (Jan 4, 2008)

The circuit works by selectively routing the track’s power through one of two 6 volt, 4PDT relays in accordance with the track polarity. The 6-volt relays are cheap and readily available. Four 3-amp diodes are attached to the wheel pickups with two providing a pathway for forward track current to one of the relays, and two providing a pathway for rearward track current to the other relay. We’ll call these the “forward” and “rearward” relays. The forward relay will always pass the “forward current” (i.e., engine moves in a forward direction) and the rearward relay will always pass rearward current (i.e., the engine moves backward). We’ll use 3 amp diodes because these diodes will carry the current of the motors and lights when the engine initially begins to accelerate.

The current from the two diodes that supply the forward relay first passes through two of the armatures (pole 1 and pole 2) of the rearward relay. Similarly, current from the two diodes that provide the rearward relay first passes through two of the armatures (pole 1 and pole 2) of the forward relay. The normally closed (NC) contacts on poles 1 and 2 for each of the relays are wired to the NC contacts 3 and 4 on the other relay. So, if the a relay is at rest, current can transfer to the other relay, whereas if the relay is active, this current goes to the normally open (NO) contact and never gets there.

The armatures for poles 3 and 4 on each relay go to a 5-volt regulator. The two regulators are aligned such that when current passes they provide 5 volts to that relay’s coil. We will use 5-volt regulators because they become active at a lower voltage than 6-volt regulators, you can cheaply series just two super caps (but unnecessary) that can hold the relay open for as long as you please, and 6 volt relays are typically reliable down to under 4.5 volts.

We’ll parallel a capacitor with each relay coil. This capacitor charges when the relay is active and will determine how long the relay stays closed once the coil voltage is removed. We may also want to use a resistor/variable resistor in parallel with this capacitor so we can “bleed off current” to adjust the time, if the capacitor holds the relay closed longer than desired. We only need to hold the relay closed long enough so that it stays closed for the duration of time that it takes for the track voltage to flip (milliseconds), but may want this time to be a bit longer, as I will discuss below.

As noted, the armatures for poles 3 and 4 on each relay go to a 5-volt regulator. For the forward relay they also go to two 3-amp diodes, then to the motor/lights contacts, so that forward current can flow through the diodes to the motors when it is present at the relay armature. We’ll do the same thing on the rearward relay so that reverse current can flow to the motors when present at that relay. The diodes keep the “wrong current” out of the voltage regulators when the engine is going in the opposite direction.

As an alternative, the armatures for poles 3 and 4 on each relay can go directly to the motor/lights contacts without going through the 3 amp diodes. Instead we can use 1-amp diodes after the union of the two relays to the motors to ensure that the proper regulator and relay coil is activated. The open contacts in the active relay will keep the voltage to the motors from “back flowing” and going “the wrong way” creating a short circuit.

The difference between the two methods, other than the cost of 1 vs 3 amp diodes, is the slight loss of voltage to the motors, or to the regulators/relays. If we use the 3 amp diodes after the regulator/relays, the motors have a 2.8-volt reduction from their supply source because current passes through two sets of diodes. But the current to the voltage regulators only goes through 1 set of diodes so they “see” their operating voltage quicker.

On the other hand, if the 1 amp diodes are used, the motors see a reduction of 1.4 volts, because the current only goes through 1 set of diodes, but the current to the voltage regulators must go through two sets of diodes before closing the relays and allowing the engine to ignore voltage reversals thereby lowering its “sensitivity.”

Assuming that one has sufficient voltage in their power supply to account for the small difference in speed, I would opt to use the 3 amp diode method (i.e., 2.8 volt drop to the motors), which has other benefits I’ll discuss.

In addition to the four 3-amp diodes at the wheel pickups that route current to the two relays discussed above, we will put a bridge rectifier with the a/c taps on the wheel pickups. We’ll wire the + and – to the NO contacts on poles 3 and 4 such that when the forward relay is activated, forward current will pass to the armatures. We’ll “cross” these wires to the NO contacts on poles 3 and 4 of the rearward relay such that when the rearward relay is activated, rearward current passes to its armatures.

And that’s it for the components and wiring.

So how does it operate???

Say the user selects forward and ramps up the voltage. Current flows to the forward relay and out to the motors. As the voltage is increased the regulator closes the relay and the voltage to the motors is now taken from the bridge rectifier. As the track current flips, the capacitor holds the relay closed for a moment and the bridge rectifier still supplies the forward current. The engine is now “swimming against the current.”

The “now reverse” current on the track can’t make its way to the reverse relay through its diodes because it must first pass through the normally closed contacts of the forward relay that are now open. This prevents a short circuit.

The same situation occurs if we start out in the rearward direction except that the rearward relay engages, etc.

So what happens when the engine slows down, why would one want to extend the time the relay is held by the capacitor, and how do the diodes to the regulators/motors impact this?

As the engine slows down it will continue to travel in the direction it is headed as long as the relay is held closed. But as the speed ramps down, eventually the voltage will drop low enough for the relay to open and the engine will revert to the direction that the current is flowing. If the engine is “swimming with the current” when the relay opens… great! But if the engine was swimming against the current and ramping down with a long momentum there is the possibility that you could get a bit of a “kick back” if the engine is very sensitive to low voltages (


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## Del Tapparo (Jan 4, 2008)

No 555's?


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## Garratt (Sep 15, 2012)

Posted By astrayelmgod on 19 May 2013 10:48 AM 
I see you guys haven't been keeping up with the latest in patent "innovations". To pick one notorious example, Amazon has a patent on the concept of buying something with a single click. Not the process, not the implementation, but the concept itself. 
What they think they have achieved and what you think they have achieved with a piece of paper is simply an impression of what is actually true until it is put to test. 
The specific point here is that you can't buy something with a single click. One would have to set-up an account with payment and delivery details first. They have formal rights to their own delusion.
--------------------------------- 

Todd, what about locos that have multiple pick-ups on different axles? Most do. A loco straddling a gap of polarity reversal would short circuit unless you were switching the polarity for each electrical pick-up point.
Am I missing something here? 

Andrew


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## toddalin (Jan 4, 2008)

Posted By Garratt on 19 May 2013 08:26 PM 
Posted By astrayelmgod on 19 May 2013 10:48 AM 
I see you guys haven't been keeping up with the latest in patent "innovations". To pick one notorious example, Amazon has a patent on the concept of buying something with a single click. Not the process, not the implementation, but the concept itself. 
What they think they have achieved and what you think they have achieved with a piece of paper is simply an impression of what is actually true until it is put to test. 
--------------------------------- 

Todd, what about locos that have multiple pick-ups on different axles? Most do. A loco straddling a gap of polarity reversal would short circuit unless you were switching the polarity for each electrical pick-up point.
Am I missing something here? 

Andrew 


In our case, we are tapping off the internal wires that connect the axles to the train's internal circuit board and splice in at this point. This has nothing to do with bridging gaps and that is handled in the traditional fashion. This is only to keep engines from switching directions when the track current is reversed.


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## Garratt (Sep 15, 2012)

Todd, 

I get you now. Thanks.

Andrew


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## toddalin (Jan 4, 2008)

It may also be viewed as a "safety device" for your engine.

Ever had a train making its way down the line and someone "accidently" throws it into reverse? That can be really hard on the gears if the reversal is instantaneous, like on the MRC 6200.

With this installed, the reversal would be ignored and the train would continue on its heading.


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