Voltage drop

[bike2steam]

Interesting thread, the only time I've had a voltage drop on a layout was due to a dry-joint in a 'D' connector, easily traced, but I do tend to rush my soldering on electrics. I can't understand this melting of sleepers, with the right iron, solder, and flux, and a good clean up of the area to be soldered - it should be no problem.

Edited July 30, 2017 by bike2steam

[Crosland]

The voltage drop thing is interesting, I'm starting to think the people with voltage drop problems need to get a decent controller. One which controls voltage. Not wattage.

 

All conventional model railway controllers are voltage controllers in one form or another. They control the voltage at their output. Voltage drop occurs due to resistance in the layout (wiring and trackwork).

 

No controller can compensate for that unless it monitors the voltage at remote point of the layout. The only way would be to raise the output voltage affectin operation closer to the controller.

[amdaley]

 

 

The voltage drop thing is interesting, I'm starting to think the people with voltage drop problems need to get a decent controller. One which controls voltage. Not wattage.

 

 

All the power in the world is useless unless you can get it to the other end of the layout & there's only one sure way of doing that.

Proper wiring.

[tigerburnie]

I need a better higher wattage soldering iron, that will help, need to get out and get one tomorrow. The Gaugemaster does control the voltage, I've checked as I bought the controller secondhand, I am thinking about using another controller for the goods loops and "countryside section\" that will be on the opposite side of the oval.

[AndyID]

 

The voltage drop thing is interesting, I'm starting to think the people with voltage drop problems need to get a decent controller. One which controls voltage. Not wattage.

 

Can't say I ever heard of a controller that controls wattage. AFAIK, one way or another, they all control voltage.

 

The voltage drop problem is (usually) caused by the resistance in the rails themselves. It's not difficult to understand what's going on if you think of them as resistors that are carrying current to and from the motor and apply a Ohm's Law.

[AndyID]

Wiring loo, I made the mistake of using common return for all of one station area of a layout and the mental gymnastics required to understand resulting weird faults was challenging. Much easier when you can put isolators and switched feeds in either polarity rail.

 

No mental gymnastics are required if you follow a few simple rules. You end up with something that's far less complicated, more reliable, and you won't have problems when you hand-off a train from one controller to another.

 

(See post 61 above for suggested wiring)

[DCB]

All conventional model railway controllers are voltage controllers in one form or another. They control the voltage at their output. Voltage drop occurs due to resistance in the layout (wiring and trackwork).

 

No controller can compensate for that unless it monitors the voltage at remote point of the layout. The only way would be to raise the output voltage affectin operation closer to the controller.

 

 

Can't say I ever heard of a controller that controls wattage. AFAIK, one way or another, they all control voltage.

 

The voltage drop problem is (usually) caused by the resistance in the rails themselves. It's not difficult to understand what's going on if you think of them as resistors that are carrying current to and from the motor and apply a Ohm's Law.

 

Most controllers control Watts, VA  a setting for instance say 1/2 maximum speed can provide 6 watts, 6VA, 6 volts 1 amp, uphill 12 volts 1/2 amp downhill.  Slow up, fast down.

 

Voltage control units vary the voltage, 1/2 speed shall we say 6 volts,  6 volts 1 amp up hill 12 VA 12 watts, 6 volts 0.1 amp  1.2 watts 1.2VA downhill so the speed stays very much more stable than the usual PWM or (especially) Resistance controls.  The difference between the two is quite striking especially when recent Bachmann and Hornby locos are running on an undulating layout, like in my loft.   On the other hand I don't get any slowing on the far side of the layout from the single power clip some 18 feet with a resistance controller, the slowing is gradient related as is the helter skelter rush down the other side.   Check out a Morley or OnTrack controller.

 

On the other hand every single fishplate has had to be replaced on the outside branch and many have bridging wires added and we have a program of drilling the 1/2" thick baseboards to fit droppers, as well as live frog polarity switches due to constant problems, greatly reduced by banning old X04 motored locos and using an N gauge 9 volt 1/2 amp controller instead of a 1 amp 12 volt unit. 

Edited July 31, 2017 by DavidCBroad

[DCB]

No mental gymnastics are required if you follow a few simple rules. You end up with something that's far less complicated, more reliable, and you won't have problems when you hand-off a train from one controller to another.

 

(See post 61 above for suggested wiring)

Really?  What happens when you want to isolate the "Common" side of a siding, you have to run two wires to the switch, to an isolator switch and back or you get weird results.

if you don't go common you can just run a wire from the panel to the isolated section and one wire to the track, on either side.

Like I said wiring part of my layout Common Return was a mistake. This evening section switch 11 fed from the panel on the "Common" side was left on with Evening Star on it.  and the loco stopped with a point against it, 10 minutes later a combination of point settings (electrofrog) reversed the polarity of the unswitched rail and while we were running trains on a different part of the layout the damn thing moved 2 inches to short the point out and stop most of the layout. Even with sections it took a good 10 minutes to find what was wrong, and even then it took a great deal of thinking to work out what had gone wrong.

[AndyID]

Most controllers control Watts, VA  a setting for instance say 1/2 maximum speed can provide 6 watts, 6VA, 6 volts 1 amp, uphill 12 volts 1/2 amp downhill.  Slow up, fast down.

 

Voltage control units vary the voltage, 1/2 speed shall we say 6 volts,  6 volts 1 amp up hill 12 VA 12 watts, 6 volts 0.1 amp  1.2 watts 1.2VA downhill so the speed stays very much more stable than the usual PWM or (especially) Resistance controls.  The difference between the two is quite striking especially when recent Bachmann and Hornby locos are running on an undulating layout, like in my loft.   On the other hand I don't get any slowing on the far side of the layout from the single power clip some 18 feet with a resistance controller, the slowing is gradient related as is the helter skelter rush down the other side.   Check out a Morley or OnTrack controller.

 

 

As previously mentioned I don't know of any controllers that do anything other than control the voltage. The current and therefore the power delivered from the controller depends on the particular motor and the load on the motor at any point in time. Some controllers output a steady voltage that is determined by the controller setting and other controllers use the setting to vary the width of a pulse stream output which is another method of varying the average output voltage.

 

Some controllers also use some sort of feedback to control the voltage to try to keep the motor at constant speed.

 

Traditional rheostat controllers are really just variable resistors in series with the motor. Because the voltage they output varies with the load on the motor they don't do a very good job of maintaining constant speed.

[AndyID]

What happens when you want to isolate the "Common" side of a siding,

 

 

The simple answer is "Don't do that!" Isolation should always be on the "feed" side. The only exception might be if you are relying on the contacts in a turnout to isolate a siding but in that case it really better be a dead-end siding and not some sort of loop. If it is some sort of loop you will get into a real pickle and probably experience the sort of problem you had the other evening.

[Crosland]

Most controllers control Watts, VA  a setting for instance say 1/2 maximum speed can provide 6 watts, 6VA, 6 volts 1 amp, uphill 12 volts 1/2 amp downhill.  Slow up, fast down.

 

Voltage control units vary the voltage, 1/2 speed shall we say 6 volts,  6 volts 1 amp up hill 12 VA 12 watts, 6 volts 0.1 amp  1.2 watts 1.2VA downhill so the speed stays very much more stable than the usual PWM or (especially) Resistance controls.  The difference between the two is quite striking especially when recent Bachmann and Hornby locos are running on an undulating layout, like in my loft.   On the other hand I don't get any slowing on the far side of the layout from the single power clip some 18 feet with a resistance controller, the slowing is gradient related as is the helter skelter rush down the other side.   Check out a Morley or OnTrack controller.

No, they all vary the output voltage, subject to a maximum power output.

 

What you are describing is the difference between a crude controller with poor regulation and a decent controller with internal feedback that provides good regulation.

[DCB]

No, they all vary the output voltage, subject to a maximum power output.

 

What you are describing is the difference between a crude controller with poor regulation and a decent controller with internal feedback that provides good regulation

Ontrack and Morley deliver less than 1 volt off load.  the voltage rises with the control knob.  Take a controller and put a voltmeter across the output (off load).  Crack the slider or knob to minimum speed and read the voltage. Most are 16-19 volts off load. OnTrack less than 1 volt.

I will do a video of the OnTrack later.

I guess Crosland does not have access to a Morley or OnTrack. they rely on a single Potentiometer to give speed and reverse control, the remote has only 3 wires....

 Hammant and Morgan variable transformers don't have such a low minimum voltage, nor do Playcraft diode based control units or my home made versions, but all give silky smooth low speed running and with modern mechs very stable speed over a wide range of up and down gradients with no need to adjust the speed control.  The downside is they don't start as well as PWM with old fashioned Triang type motors and you have to develop a delicate touch on the speed control.

[tigerburnie]

Bit too hot up in the loft to do a lot but I am trying to progress along a bit each week. The panel is fitted to a hinge to allow easy access if required, the wires are not soldered yet, having done a continuity test, I will run locos along to ensure it is doing what I want it to do.

 

[kevinlms]

Ontrack and Morley deliver less than 1 volt off load.  the voltage rises with the control knob.  Take a controller and put a voltmeter across the output (off load).  Crack the slider or knob to minimum speed and read the voltage. Most are 16-19 volts off load. OnTrack less than 1 volt.

I will do a video of the OnTrack later.

I guess Crosland does not have access to a Morley or OnTrack. they rely on a single Potentiometer to give speed and reverse control, the remote has only 3 wires....

 Hammant and Morgan variable transformers don't have such a low minimum voltage, nor do Playcraft diode based control units or my home made versions, but all give silky smooth low speed running and with modern mechs very stable speed over a wide range of up and down gradients with no need to adjust the speed control.  The downside is they don't start as well as PWM with old fashioned Triang type motors and you have to develop a delicate touch on the speed control.

But none of them 'vary the Watts' as per your earlier claim.

 

 A transistorised controller varies the volts and a resistance controller, varies the current, by reducing resistance to the circuit as you turn it up.

[AndyID]

Bit too hot up in the loft to do a lot but I am trying to progress along a bit each week. The panel is fitted to a hinge to allow easy access if required, the wires are not soldered yet, having done a continuity test, I will run locos along to ensure it is doing what I want it to do.

 

Mind how you go with those screw block connector strips. They have a nasty habit creating a faulty connection after a while when used with stranded wire.

[kevinlms]

Mind how you go with those screw block connector strips. They have a nasty habit creating a faulty connection after a while when used with stranded wire.

The problem with them I find is that if you tighten them too tight, the cheap brass distorts and can't be used again.

[Gordon H]

Ontrack and Morley deliver less than 1 volt off load.  the voltage rises with the control knob.  Take a controller and put a voltmeter across the output (off load).  Crack the slider or knob to minimum speed and read the voltage. Most are 16-19 volts off load. OnTrack less than 1 volt.

I will do a video of the OnTrack later.

I guess Crosland does not have access to a Morley or OnTrack. they rely on a single Potentiometer to give speed and reverse control, the remote has only 3 wires....

 

So, the Ontrack and Morley controllers are variable voltage, just like Crosland said.

The Variable resistance type of controller will obviously give a high off-load voltage because that is the nature of their design, as described by Kevinlms.

 

What type do you claim gives a 'variable wattage' output? Please provide a circuit diagram for such a device (if you have one).

 

A single pot controller with reverse is not that difficult to arrange if you know how.

[AndyID]

 

A single pot controller with reverse is not that difficult to arrange if you know how.

 

At the risk of drifting (even further) off topic, I plan to use single knob "push-pull" controllers that swing positive and negative about zero. They will all run off one dual rail power supply and they will be compatible with common-return wiring.

[DCB]

So, the Ontrack and Morley controllers are variable voltage, just like Crosland said.

The Variable resistance type of controller will obviously give a high off-load voltage because that is the nature of their design, as described by Kevinlms.

 

What type do you claim gives a 'variable wattage' output? Please provide a circuit diagram for such a device (if you have one).

 

A single pot controller with reverse is not that difficult to arrange if you know 

Resistance controllers typically deliver a minimum setting voltage of 18/19 volts off load.

 

Of the variable voltage variety the OnTrack. I measured it gave from 0 volts off load in the centre "Off" position progressively up through the 3-4 volt range where locos start to move to the maximum.   H&M Safety Minor, variable Transformers, started around 2.5 volts 

My diode based beast starts at around 5 volts,I never actually measured it, as its for Hornby Dublo locos,  but when overloaded it will trip a 1 amp breaker at minmum setting.

 

Motor speed is related to voltage, more volts more speed other things being equal, conversely the more load you put on the loco or motor the more amps it draws, with a variable resistor as the VA remains constant the motor is only able to draw more amps by slowing down,

 

With a variable voltage unit the motor draws more amps keeping the voltage and speed very nearly constant (less losses) by varying the amps and VA (Watts).    

 

Take my 28XX. it runs quite slowly on a Triang controller (Variable resistance) until it collides with the buffers which stop it dead.   On the OnTrack running at the same slow speed when it hits the buffers the driving wheels barely slow as it sits there slipping its wheels.  On the OnTrack It goes much the same plodding speed up a 1 in 50 with 20 wagons as it does back down yet can run at a scale 65 mph if required.  On the Triang (for example the Duette is every bit as bad) it needs a high power setting to climb the bank and almost zero to descend, it has to be driven all the time and I like to just set the speed and sit back and watch

 

Using voltage drop in another context on starting a typical Bachmann Pannier the OnTrack drops the voltage less than 1/2  (One half) volt from the off load value, The test was run the engine, isolate it check the Off Load volts, flip the isolator back on recheck the volts.  The Triang drops it 15  (Fifteen) volts from off load.   Both start the Bachmann pannier at 3.5 volts.

 

Think of it like this, Volts = Speed     Variable Voltage = the controller knob varies the Speed   Variable Resistor = the controller knob varies the power.

Edited August 2, 2017 by DavidCBroad

[John Tomlinson]

But none of them 'vary the Watts' as per your earlier claim.

 

 A transistorised controller varies the volts and a resistance controller, varies the current, by reducing resistance to the circuit as you turn it up.

 

Funny that I've just read this the day after watching some You Tube pieces about Hornby Dublo repairs and maintenance.

 

The producer had exactly the same opinion, and demonstrated it using his multimeter, first using an ancient HD controller, then with a Gaugemaster example, which I assume is "transistorised".

 

As far as power loss is concerned on track distant from feeds, my own experience is that it is simply cured by extra wires to a suitable point, as noted above.

 

John.

[tigerburnie]

Soldered up the switches today and continued fixing down track, this image shows the individual loops power supply, I need to now whittle down some sleepers to fill the gaps, the new variable soldering iron is making the whole job so much easier. You can also just see the V2 kit built, that I made some 30 years ago, I really must finish it and give it a lick of paint.

[bike2steam]

That nearest siding, next to the turnout doesn't look right, are you using a Tracksetta to set your curves ? 

[tigerburnie]

That short piece of flexible isn't fixed down and it's flexed a bit, it will be set correctly, it's due to get loops soldered across the joins first.

[AlbertTheFrog]

Mind how you go with those screw block connector strips. They have a nasty habit creating a faulty connection after a while when used with stranded wire.

In my (French, admittedly!) club we make a lot of use of choc blocks, but we always use ferrules on the end of flexi cable. We have one permanent (but transportable once or twice a year) layout that is about 90ft long including the back return loops. 

 

This sort of thing

 

http://www.tme.eu/en/katalog/bootlace-ferrules_100041/

[Crosland]

Resistance controllers typically deliver a minimum setting voltage of 18/19 volts off load.

That's what is meant by poor regulation. Much the same as a transformers output will vary with load whereas a regulated supply will not.

 

Motor speed is related to voltage, more volts more speed other things being equal, conversely the more load you put on the loco or motor the more amps it draws, with a variable resistor as the VA remains constant the motor is only able to draw more amps by slowing down,

 

With a variable voltage unit the motor draws more amps keeping the voltage and speed very nearly constant (less losses) by varying the amps and VA (Watts).

All down to the quality of the regulation. A resistance controller as a very high source impedance and cannot regulate the output voltage as tightly. It is still trying to control the voltage but as soon as you draw any current the controller's resistance causes a voltage drop, reducing the voltage available at the output.

 

Take my 28XX. it runs quite slowly on a Triang controller (Variable resistance) until it collides with the buffers which stop it dead.   On the OnTrack running at the same slow speed when it hits the buffers the driving wheels barely slow as it sits there slipping its wheels.  On the OnTrack It goes much the same plodding speed up a 1 in 50 with 20 wagons as it does back down yet can run at a scale 65 mph if required.  On the Triang (for example the Duette is every bit as bad) it needs a high power setting to climb the bank and almost zero to descend, it has to be driven all the time and I like to just set the speed and sit back and watch

Again, just artifacts of poor regulation v. good regulation.

 

Think of it like this, Volts = Speed     Variable Voltage = the controller knob varies the Speed   Variable Resistor = the controller knob varies the power.

 

That's just muddled thinking. Apply ohms law and you will understand what is going on.