A 5 volt Model Railway
Posted: Thu Oct 29, 2020 7:50 pm
Those who think that CSBs are a step too far, may not expect to see any of this in the Snews...
It seems to me to be a logical progression from radio control and single battery cells, given the ubiquitousness of 5 volt USB chargers for smartphones, smartwatches, iPads, MP3/4 players, remote speakers and now even AA cells, that model railways could go to 5 volt supplies.
The Li-Po batteries in most of these desirables now have sophisticated control/protection circuits built in, so that without any more components they can be left on charge from a USB port overnight, or for even longer. Further, the item can be left 'on' indefinitely to the point that the control circuit shuts the supply down before the battery is damaged or the house burns down. They are available in a surprising range of sizes, both physical and capacity, to suit any tank, tender or fuel tank one may wish to fit.
The question that has been an issue for some time has been how to charge a battery that is inside a loco. Any method that involves handling the model is clearly inhibiting, so the advantage of the common and traditional pickups from the rails via the wheels is obvious. So I choose to keep them.
Traditionally, our tracks have a varying up to 12 volts DC across them according to the desired speed of the loco, the polarity reversing according to the desired direction of travel. The somewhat less traditional DCC system requires around 16 volts AC across the tracks constantly. Both rely on a consistent quality of current collection to maintain smooth running, or extra components in each loco to compensate for interruptions in the collection, but neither cope with short circuits across the tracks particularly successfully.
That is because until recent advances in technology, much more powerful magnets especially, DC motors could not be made small enough or sufficiently powerful at the size needed to fit inside our models if supplied at a lower pressure. The reason that DCC requires a higher voltage to drive 12 volt motors is because of losses in the rectification to DC and control systems used.
There's an old joke that ends with "Well, I wouldn't start from here!"
Starting with the Li-Po battery, a single cell - called 1S, has a nominal output voltage of 3.7 volts. This clearly requires a motor which provides sufficient torque at that voltage, to drive a loco in a manner similar to the 12 volt motors that we are used to. There is a large range of motors now available that are suitable.
So, a battery, the radio receiver - equivalent to a DCC chip - is all that is needed in the loco, or tender if it has one.
A minor difficulty here is that the USB supply is DC, and so is the battery and receiver, so the loco could only be run one way round, or the supply would need to be changed with a reversing DPDT switch. But that would only be required when the loco is on a charging track. The rest of the time, the loco would not need to pick up current as the battery supplies this, a sort of inverse of the 'stay alive' concept.
On the other hand, only one extra component - a bridge rectifier - would be needed in each loco to correct the polarity so that it wouldn't matter which way round either the loco or the track polarity was.
Pros:- Only charging tracks need be wired. These could be adjacent to water columns or in shed areas, or even either side of water troughs, how often do we see those modelled? Or more modern, by diesel fuelling points. Shades of getting it all right!
Pointwork need not be wired at all.
Running the wrong way into a point set against would not cause a short with a rectifier fitted to the loco, as this prevents current flowing from the pickups back to the track.
Stock works perfectly well on rusty sidings as the rails need not supply current. No more painful track cleaning except on the few, straight, charging tracks.
Cons:-
Existing locos with 12 volt motors can still be accommodated by adding just one more component, a voltage booster between the battery and the receiver. The Pololu U3V12F12 is tiny, costs around $4 U.S. and can supply over 1A. There are a number of alternatives, many of them with adjustable output voltages on eBay. These are a bit larger and the ones I have can supply up to 2A, though this is rarely needed in 4mm scale.
If the track is normally supplied with 12 volts DC or 16 volts AC, a couple more, still small, components may be required for radio control. After the rectifier,a voltage regulator, and there are now much smaller ones available than that I used in the 14xx, to provide 5 volts for a 1S battery, and then a booster if the motor is still a 12 volt one.
I currently have three locos running on USB supply, the Simplex in my S4-9? topic, the WD 2-8-0 that I demonstrated at CHEAG before the C19 interruption, and a Collett Goods with High Level running gear. The WD retains the Bachmann pickups and motor, but now has a new 850mAh battery in the tender. The Collett is pure 5 volt, with experimentally a pair of 200mAh batteries wired in parallel in the tender, and an FF-130 motor on a High Level 40:1 'box. Even with the added traction of a CSB chassis, it spins the wheels freely against the buffer stops. There will be a 30:1 'box in the next one.
This is the Collett tender chassis. Pickups are 33swg p/b, arranged as stylus at the ends as I find that this keeps the wheel treads clean. A bridge rectifier is fitted to the small piece of stripboard. The receiver is slotted into a piece of unshrunk shrink-wrap glued to the lead weight.
Ted.
It seems to me to be a logical progression from radio control and single battery cells, given the ubiquitousness of 5 volt USB chargers for smartphones, smartwatches, iPads, MP3/4 players, remote speakers and now even AA cells, that model railways could go to 5 volt supplies.
The Li-Po batteries in most of these desirables now have sophisticated control/protection circuits built in, so that without any more components they can be left on charge from a USB port overnight, or for even longer. Further, the item can be left 'on' indefinitely to the point that the control circuit shuts the supply down before the battery is damaged or the house burns down. They are available in a surprising range of sizes, both physical and capacity, to suit any tank, tender or fuel tank one may wish to fit.
The question that has been an issue for some time has been how to charge a battery that is inside a loco. Any method that involves handling the model is clearly inhibiting, so the advantage of the common and traditional pickups from the rails via the wheels is obvious. So I choose to keep them.
Traditionally, our tracks have a varying up to 12 volts DC across them according to the desired speed of the loco, the polarity reversing according to the desired direction of travel. The somewhat less traditional DCC system requires around 16 volts AC across the tracks constantly. Both rely on a consistent quality of current collection to maintain smooth running, or extra components in each loco to compensate for interruptions in the collection, but neither cope with short circuits across the tracks particularly successfully.
That is because until recent advances in technology, much more powerful magnets especially, DC motors could not be made small enough or sufficiently powerful at the size needed to fit inside our models if supplied at a lower pressure. The reason that DCC requires a higher voltage to drive 12 volt motors is because of losses in the rectification to DC and control systems used.
There's an old joke that ends with "Well, I wouldn't start from here!"
Starting with the Li-Po battery, a single cell - called 1S, has a nominal output voltage of 3.7 volts. This clearly requires a motor which provides sufficient torque at that voltage, to drive a loco in a manner similar to the 12 volt motors that we are used to. There is a large range of motors now available that are suitable.
So, a battery, the radio receiver - equivalent to a DCC chip - is all that is needed in the loco, or tender if it has one.
A minor difficulty here is that the USB supply is DC, and so is the battery and receiver, so the loco could only be run one way round, or the supply would need to be changed with a reversing DPDT switch. But that would only be required when the loco is on a charging track. The rest of the time, the loco would not need to pick up current as the battery supplies this, a sort of inverse of the 'stay alive' concept.
On the other hand, only one extra component - a bridge rectifier - would be needed in each loco to correct the polarity so that it wouldn't matter which way round either the loco or the track polarity was.
Pros:- Only charging tracks need be wired. These could be adjacent to water columns or in shed areas, or even either side of water troughs, how often do we see those modelled? Or more modern, by diesel fuelling points. Shades of getting it all right!
Pointwork need not be wired at all.
Running the wrong way into a point set against would not cause a short with a rectifier fitted to the loco, as this prevents current flowing from the pickups back to the track.
Stock works perfectly well on rusty sidings as the rails need not supply current. No more painful track cleaning except on the few, straight, charging tracks.
Cons:-
Existing locos with 12 volt motors can still be accommodated by adding just one more component, a voltage booster between the battery and the receiver. The Pololu U3V12F12 is tiny, costs around $4 U.S. and can supply over 1A. There are a number of alternatives, many of them with adjustable output voltages on eBay. These are a bit larger and the ones I have can supply up to 2A, though this is rarely needed in 4mm scale.
If the track is normally supplied with 12 volts DC or 16 volts AC, a couple more, still small, components may be required for radio control. After the rectifier,a voltage regulator, and there are now much smaller ones available than that I used in the 14xx, to provide 5 volts for a 1S battery, and then a booster if the motor is still a 12 volt one.
I currently have three locos running on USB supply, the Simplex in my S4-9? topic, the WD 2-8-0 that I demonstrated at CHEAG before the C19 interruption, and a Collett Goods with High Level running gear. The WD retains the Bachmann pickups and motor, but now has a new 850mAh battery in the tender. The Collett is pure 5 volt, with experimentally a pair of 200mAh batteries wired in parallel in the tender, and an FF-130 motor on a High Level 40:1 'box. Even with the added traction of a CSB chassis, it spins the wheels freely against the buffer stops. There will be a 30:1 'box in the next one.
This is the Collett tender chassis. Pickups are 33swg p/b, arranged as stylus at the ends as I find that this keeps the wheel treads clean. A bridge rectifier is fitted to the small piece of stripboard. The receiver is slotted into a piece of unshrunk shrink-wrap glued to the lead weight.
Ted.