Surge on startup

[ModelerXYZ]

Hey Guys,

I am planning the controls of my new railway. Current surges on startup with m otors are normal. I play with DC trains only. I don't like DCC, I have tried it. Would it be possible to put a push to make switch on a seperate power supply to provide a sudden bit of extra oomph for starting big locos? I know this would be a question that the late Chrissaf would have given me a pointer on, but he is no longer with us.

XYZ

[ColinB]

So why don't you just buy a bigger power supply.

[Yelrow]

XYZ, hi, i am big in DC, and cos i have Hornby Dublo 3 rail, need a bit more grunt at start up. Solution. Hamment and Morgan, Duette, or Clipper, of which, i have several. Even My Big Boy, and Challenger locos, pull away well.

[96RAF]

You are looking for the DC equivalent of DCC CV2 - kick start voltage. Outwith my skill set, so I leave it to the DC guys.

[ModelerXYZ]

I have a HM2000 which will be doing most of the work. But I wanted to consider if I could possibly just put a little more Oomph into it for the current surge starting a loco needs. It should start most of the time except when the track is dirty.

[Yelrow]

I have 2, HM2000 s, I am afraid they don’t compare in my view with a Duette. When 3 rail began the weight of these locos meant you needed more grunt to pull away, even more with heavy coaches behind. Hence H&M came up with Clipper, and Duette. Several of us , on here use these daily.

[CORKY.]

My boys used to run Playmobil electric GScale train sets, if we ran two or more electric motors in the consist, we used an extra power controller, from a set , coupled to the track in the normal way, to turn up the power to the motors when needed. Also worked well for our later two LGB EMD F7A units when running together (4 motors) No cutting out, no fuses blew, and it made good use of the spare low power controllers from the Playmobil sets. My impression was though that anything Playmobil and LGB was rugged well engineered quality and built to last. So for us, just using an extra controller worked well.

[96RAF]

@xyz

...there is no way you can ‘boost’ the controlled output of an HM2000 to achieve what you are considering.

[Yelrow]

It’s ok for modern stuff. My 2 are fit for purpose, and well built. But try to move a 3 rail Duchess with 4 coaches, taint quick, till it builds up. Put a Duette in its place, marked improvement. We get spoilt by modern lightweight Locos, and modern motors.

[Topcat2018]

@MO

In theory it would be possible to provide a current pulse to start a loco by using one of the uncontrolled outputs to charge a large capacitor, which could briefly be connected to the track by a switch to provided a current boost.

There are a number of practical problems.

1. As the polarity of the controller can be reversed to reverse the train's direction you would have to be able to reverse the polarity of the boost pulse.
2. I don't think you would want to connect the boost signal direct to the controller output as it might cause damage.
3. If the loco was in a stalled condition with the controller in current limit, how quickly would the controller come out of current limit when the boost pulse was applied, which would determine the length of boost pulse required?
4. I think it might be best to rectify the uncontrolled AC output and use this to provide the boost signal and prevent this getting back to the controller outputs using isolating diodes. The forward voltage of these would lose you about 1 volt when the controller was at full output.
5. Even this solution might not be sufficient as the HM2000 can only output 430 mA and some older locos once started can still take over 500 mA with a heavy load.

Bearing this in mind, if you are still interested I could try to work out a circuit for you.

[ModelerXYZ]

Hey RAF, I wasn't going to boost it with the controlled output... I was actually thinking a completely seperate transformer to provide the surge. But go for it Topcat, I would like to see the design to find out if its a workable solution.

XYZ

[Yelrow]

XYZ, picking up a clipper or duette from ebay, in my view, would also provide a workable solution

[ellocoloco]

My two Duettes manage anything I don't let near my Multimaus. Would fully agree with Yelrow, one should provide the 'grunt' to get things going.

[Topcat2018]

@ModelerXYZ

Could you also confirm the following:

1. Does the problem occur when you wind up the controller voltage from zero?
2. What happens if you set the controller output to maximum, not connected to the track, then connect it to the track.

Do you have a multimeter? If so could you measure the following:

1. Current from controlled outputs if you just connect multimeter set to 2 amp range across them.
2. Voltage across your loco when you wind up the controller voltage from zero and it goes into the stalled condition.
3. Current drawn by your loco when it's in the stalled condition.
4. Voltage from uncontrolled DC and AC outputs with no load and nothing connected to controlled output and also when loco is stalled (i.e does current limiting of controlled output affect the other outputs).

[Topcat2018]

@ModelerXYZ

Hi again, Another suggestion I should have made. Turn the controller to maximum and give the loco a push, and see if it runs. Or try putting the loco on a piece of downward sloping track, steep enough that it is just short of slipping.

If the loco doesn't run it may be that the controller cannot supply enough current to run the loco even once you have reduced the load the motor has to drive by one of these measures.

[Yelrow]

All this supports the need for more Grunt, hence the older better controllers built for running Hornby Dublo.

[Topcat2018]

We suspect, but haven't proved, that a more powerful controller is probably the solution, but I'm trying to confirm that this is the root of XYZ's problem and eliminate any other possibilities.

For all we know it could be a problem with the loco.

[Yelrow]

Topcat, agree there might be other possibilities, but as a 00 user for 59 years, with a lot of old locos know, that they need a lot of grunt to pull away. I bought 2 ot these newer H&M 2000s, in the belief that they would replace my older ones, only to find they were not as powerful. The Duettes and Clippers have adjustable power levels, whereas, the 2000, has not. They are fine for all modern stuff, and have them on my layout where i run lighter locos. By all means, carry out your theories. I will be interested in the results. I was only explaining how i had achieved loco running with my heavy brigade.

[Topcat2018]

I don't have an HM2000 myself, but it certainly wouldn't power some of my locos. As I mentioned in a previous post I test the tractive effort of my locos and I have an old Bachmann A4 that draws over half an amp at maximum tractive effort (when wheel slip occurs).

As a (retired) electronic engineer I build pretty much all my own stuff. At the moment I just have an old Gaugemaster Series E (inherited from a friend) that current limits at 1.6 A, but I am currently building a 3 channel DC controller which will have a 1.5 amp current limit on each channel, with thermal cutouts as an extra safeguard, plus 5 V 1.5 A and 12 V 1.5 A auxiliary outputs for accessories. The controller will be powered from a 15 V 8 amp switch-mode power supply.

One thing I haven't asked XYZ is what loco(s) he is actually using.

[Yelrow]

Yup, it’s all down to loco age.

[Gordonvale]

I use a 0-15 V 60 amp switch-mode power supply to drive 27 individual DC controllers and 3 LED circuits. For protection, there's a 10A circuit breaker between the supply and the individual circuits. Each individual circuit is further protected by 4 x 5W resistors totalling 8R to permit a max of 1.5A @ 12V or 1.875A @ 15V depending on what takes my fancy on any given day.

Each "train running" circuit is controlled by a DC speed controller (various Chinese types) and works just fine as any loco that enters a circuit is already "warmed up". The shunting and storage circuits are controlled by a 100R potentiometer wired as a rheostat. These vary the resistance, not the voltage. Hence, when powered up , a loco is hit by the full 12-15V.

I've chosen this set up because I've observed that the rheostat controlled locos move off nicely. When warmed up, they move off smoothly. When cold, they move off gradually, some more gradual than others. I don't have any science to back this statement, but I'm happy with things. Also some of the smaller locos (pocket rocket 0-4-0, 0-6-0 shunters) don't come to a complete stop at 100R, because they crawl on tiny amps. To combat this I include a second rheostat (50R) in series which I label "brake". It works for me.

Whenever a loco is parked, I isolate it. I don't know why I do this, I just uneducatedly think that the tiniest current running through a motor isn't good for it if it won't move it. Points work for sidings, switches work for places like engine sheds where there are several locos on the one track.

[Yelrow]

Gordonvale, hi, Gosh that sounds frightfully complicated to me. I simply use up to 10 Duettes and Clippers, plus 2 H&M 2000, as required. I achieve perfect smooth running.

[Topcat2018]

@Gordonvale

@Yelrow

Blimey! You guys must have some complicated layouts, and lots of space. Unfortunately my shed is only 5 metres long by 2.5 metres wide.

[Yelrow]

custom built train room about 22 foot by 15 foot. I run 00. TT, Dublo 3 rail. N , and Z,gauges, with 2 Helix,s. Apart from Baseboard, also 2 track layout totally round the room. Then just for fun, DCC, as well. With 100 plus locos. Here in France, space is Not a problem.