Just curious...

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UrbanHermit
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Just curious...

Postby UrbanHermit » Fri Mar 09, 2018 11:21 am

In the course of my recent railway modelling revival I've been coaxing my locos back to life, but one of them, my Hornby 28xx, stayed resolutely dead.

Up to now I haven't bothered with long addresses, just using the last two digits of the running numbers, but having got to the stage where I have two pairs of locos with identical pairs of last digits I thought it really was about time I bit the bullet. So yesterday I set about assigning everything a long address. I use an NCE Powercab, by the way.

Now the 28xx is 2812, so I'd given it the short address 12, but when the Powercab got to the stage of reading that address it came up as 000. No wonder the thing hadn't moved when I'd used the 12 address. Sure enough, once I'd assigned it the long address 2812 it creaked into life.

Eureka, but I'm curious to know how it came to reprogram itself to the 000 address, because I certainly didn't do it. Well, not on purpose.
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alex3410
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Re: Just curious...

Postby alex3410 » Fri Mar 09, 2018 11:30 am

You might find some decoders just do it to toy with you :lol: - at least that's how it feels sometimes.

In reality, it could be down to an iffy decoder or a corrupted DCC signal, dirty track or similar that interfered with the addressing - I get the same thing especially on the cheaper decoders but normally you can readdress it easily enough.

Sometimes, however, I have had to reset the decoder before it will take a new address - if you find you cant reset the address I would try this as your next troubleshooting step. Even then sometimes its taken a few attempts to reset some particularly stubborn decoders so if it does not work the first time try it a few more times.

You will be able to tell when its reset as the address will go back to 003, also make sure wheels/track are clean as well.

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Bufferstop
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Re: Just curious...

Postby Bufferstop » Fri Mar 09, 2018 1:58 pm

Yup, amnesiac flash memory is more common than the manufacturers like to admit, especially when left unused for a longish time. It just happens from time to time. I think I've had one example of almost every sort of device that has at some time or other lost its configuration whilst not being used. Does your controller allow you to take a copy of a loco's settings. If you do much more than just set it's address keep a copy if you can, otherwise write down the CV values when you set them. One of my colleagues was convinced it was caused by random solar radiation and used to keep all of his spares in a steel locker. I thought he ought to have got himself a WW1 steel helmet.
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Re: Just curious...

Postby luckymucklebackit » Fri Mar 09, 2018 2:09 pm

Would a DCC locomotive be susceptible to an EMP? Not talking about a deliberate weapon based EMP, more thinking about that generated by a lightening strike or Solar EMP, we had some quite spectacular thunderstorms in some parts of the country, and there has been increased visibility of the Aurora Borealis?
Just a thought.

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UrbanHermit
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Re: Just curious...

Postby UrbanHermit » Fri Mar 09, 2018 3:50 pm

Thanks, all. So, it's one of those things that 'just happens,' then.

As far as I can remember, last time I ran the loco in question it stalled on some curved points (I don't use them any more), I took my time getting to it, and when I did it had gone dead. Quite likely the track wasn't as clean as it might have been, either. I was afraid I'd burnt out either the chip or the motor.

No, Alex, I had no problem resetting the address, and the loco now runs as well as ever - it's always been a little temperamental, especially after periods of disuse. It also has a nasty tendency to derail its leading pony truck on facing points, but that's another can of worms entirely.
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Bufferstop
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Re: Just curious...

Postby Bufferstop » Fri Mar 09, 2018 5:03 pm

luckymucklebackit wrote:Would a DCC locomotive be susceptible to an EMP?

Not such an odd question. In the bad old days of DC and Bands 1-3,405 line TV, the RF generated by a sparking commutator could wipe out TV for most of the street unless it was well suppressed because the track acted as a great big horizontal aerial, especially if it was mounted at eaves level, ie in the loft. Aerials are two way devices so your track can just as easily receive as transmit. I can see that a nearby lightening strike could well be picked up by your track and cause a surge current through any decoders connected and the controller. It frequently kills modems and routers connected to phone lines. The bad news is there's not a lot you can reasonably do about it. When I had an IT centre with ~100 PCs on the top floor of the highest block on the campus we ended up creating a "Faraday cage" around the whole of the top storey, inch wide copper strips radiating out of the centre of the roof and running down the vertical sides of each block of windows, all joined together and connected to a great thick cable buried deep under the carpark.
Not practical to do just to protect a few £20 decoders. I'd say make sure no part of your railway's low voltage wiring is connected to earth, any voltage induced in the track or wiring is likely is likely to be the same in both wires, and both rails. The same voltage on each rail equates to no voltage across the connected devices, so unless you are the recipient of a direct strike you should be OK.
But none of that is going to stop the odd decoder apparently losing its memory when put away and not used. My former colleague's precaution of putting things in a steel locker is probably not so daft, if these occasional failures are caused by solar radiation to which we are always exposed to then putting things in tin boxes can only help.
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UrbanHermit
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Re: Just curious...

Postby UrbanHermit » Fri Mar 09, 2018 9:39 pm

'...Doctors finding many ways
Of putting brains in metal trays
To keep us from the heat...'

('It's Good News Week', Hedgehoppers Anonymous, 1965)

Sorry, couldn't resist.
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Ironduke
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Re: Just curious...

Postby Ironduke » Fri Mar 09, 2018 9:48 pm

Never mind lightening strikes and EMP, static electricity is a major cause of electronics shenanigans and electronics manufacturers spend thousands trying to eliminate it from their factories (if they have any sense). It's the reason most decoders are shipped in an anti static bag.
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Bufferstop
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Re: Just curious...

Postby Bufferstop » Fri Mar 09, 2018 11:40 pm

One thing that you can do, if you are putting a DCC fitted loco into any kind of box is to make sure the wheels are shorted to each other, a patch of kitchen foil would do, some of that dark grey conductive foam that many computer parts are packed in would be even better. It's weird I walk around shops and offices dishing out static shocks to door plates, metalwork on counters, display shelves and anyone daft enough to offer to shake my hand, but in forty years working with electronic components, often unavoidably without any special equipment, I've never once zapped one.
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Ironduke
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Re: Just curious...

Postby Ironduke » Sat Mar 10, 2018 5:44 am

Bufferstop wrote:One thing that you can do, if you are putting a DCC fitted loco into any kind of box is to make sure the wheels are shorted to each other, a patch of kitchen foil would do, some of that dark grey conductive foam that many computer parts are packed in would be even better. It's weird I walk around shops and offices dishing out static shocks to door plates, metalwork on counters, display shelves and anyone daft enough to offer to shake my hand, but in forty years working with electronic components, often unavoidably without any special equipment, I've never once zapped one.


Adding ESD control procedures in our factory lowered the in-warranty failure rate from about 30% to about 2%. Components are most vulnerable before they are soldered to the PCB but even after that static electricity can seriously shorten the lifespan of a device.
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Re: Just curious...

Postby Bigmet » Sat Mar 10, 2018 11:06 am

The greatest hazard to any electronic device is you! No carpets on your railway room floor, these are killers for generating charge on you by the action of walking about, due in part to the insulating properties of the soles of your footwear. And always first earth yourself before handling a decoder, or a decoder fitted loco off the rails.

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Re: Just curious...

Postby End2end » Sat Mar 10, 2018 11:14 am

Bigmet wrote:And always first earth yourself before handling a decoder, or a decoder fitted loco off the rails.

I dispell static by touching a radiator. Been doing it this way before delving into the guts of computers for years.
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