I recently purchased my first DCC system (Digitrax Super Chief Xtra) and by mere coincidence I have this winter been getting a lot of static electricity in my layout room. It has the same carpeting, I am waring the same cross-trainer shoes for the last 8 years, i.e. nothing changed to environment. Anyway, should I be concerned about the effect on decoders and hardware? sometimes I get zapped if I contact track or something else. I notice there is a plug for "GRD" on the DCS100-should I use that as a precaution? and to what would I ground it to? Thanks all.
The use of the 'ground' connection in Digitrax is a sure fire way to cause a huge argument on the Digitrax Yahoo group. Mainly because it should more accurately be called common, not ground - if you have multiple boosters, or a PM42, or some other specific devices, there should be a heavy guage (like your track bus) wire between the ground terminals of all such devices. This provides the circuit common reference for all the devices - without the seperate wire, this reference is throught he thing phone wire of the Loconet. This reference is used by boosters and the PM42 to detect shorts and to reversing - so considering the full current of the booster could potentially flow through there, letting that happen on the thin wire of the Loconet cabling is not a good idea.
The power supply specified to step down the AC power to feed the command station/booster are these days double insulated and isolated, in that the AC house ground is not passed through - some of them don't even have a 3 prong AC plug. This keeps the layout completely isolated fromt he 120VAC house wiring - generally a good thing. If you want a bleed off for static, you can do what is used for static wrist straps - connect the ground to an AC ground or cold water pipe with a 1 megaohm resistor. The resistor makes it so that if you are touching ground with one hand, and touch a hot wire with the other, the current flow will be very feeble. Static can still bleed off.
It's a good idea to make sure you discharge yourself before touching things like decoders. Once in circuit, there are usually enough pathways to bleed off the charge without it going straight to the sensitive components, but don't zap yourself straight into a decoder fresh out of the package. Some anti-static spray on the carpet can do wonders, too.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
When you install decoders you should take the same precautions as you would when installing computer components.
Static Electricity = BAD
1) Discharge yourself when arriving at your work bench
2) touch the ground on both the locomotive and the decoder chip before starting. The metal frame of the locomotive is sufficient for this. where ground is on a decoder chip is anybody's guess, but having grounded yourself prior to opening the package, you should be ok. Remember never to touch the circuit board or its connectors.
ROAR
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Here there be cats. LIONS with CAMERAS
Static likes cold and dry. Adding some humidity would help.
Wearing shoes on a carpet, that is how you create static electricity.
Don't hook up the GND terminal to earth, as it is really a digital common so everything on the Loconet sees the same reference point. It is to connect other boosters, PM42s, and the like so they all have a common point and don't rely on the Loconet cable to provide it.
If your power supply is in a metal case, it is probably grounded to earth so touching it would drain any charge you've accumulated.
Maybe try another pair of shoes, or an antistatic treatment on the carpet. Or one of those antistatic straps that go on footwear to drain the charge back to the floor.
Static is a problem that I also had. The solution - add humidity. I bought a humidifier to bring the humidity to around 40% and the static problem went away. This may not help if its a carpet issue but my area is carpeted and had static prior to humidification. An easy solution.
Ron K.
I use some Static Spray for clothes out of the Dryer
Works great but doesn't really last long enough for me!
At least I have a nice fresh scent in the basement for a while! ;-)
BOB H - Clarion, PA
Interesting information on the Digitrax system.
I am surprised Digitrax didn't accamodate using a good earth ground for their system!
CVP's EasyDCC recommends using a good earth ground for their's.
Because I have radio towers and am at the end of a mile of transmission line from the local utility, I drove in 13 ea 8' ground rods and tied them to all the house wiring. My radial arm saw was the best ground prior to the ground rod installation. Power surges and lightning would blow the on/off switch completely across the basement. I figured replacing the switch was cheaper than replacing the well pump until the ground rods were installed.
After installing the ground rods, the only manifistations of static are the occasional displays of St. Elmo's Fire, on the ground, around the antenna farm when the ground is dry and a thunderstorm is in the area.
Jon
My experiance has been if don't touch something metal first and touch the track, locos near by will have their decoders reset. Not sure if it is surger protection in the chip or what. I have a metal step stool that I touch first and all is good.
N6VC Interesting information on the Digitrax system. I am surprised Digitrax didn't accamodate using a good earth ground for their system! CVP's EasyDCC recommends using a good earth ground for their's.
That is because modern commercial power supplies are designed to isolate one side from the other, for safety. Tying the low side to the high side voids that protection. They are designed to prevent the chassis from becoming "hot" if a failure occurs, as well as preventing you from completing the circuit.
Digitrax mislabelled their connection, as it really is a digital ground to put everything at the same level, so it will work correctly, while not relying on the loconet cable to provide that function.
betamax That is because modern commercial power supplies are designed to isolate one side from the other, for safety. Tying the low side to the high side voids that protection. They are designed to prevent the chassis from becoming "hot" if a failure occurs, as well as preventing you from completing the circuit. Digitrax mislabelled their connection, as it really is a digital ground to put everything at the same level, so it will work correctly, while not relying on the loconet cable to provide that function.
I guess I'm "old school" not modern. To my knowledge, all the transformers I use now have isolated secondaries, but I still ground everything I can. On my old DC layout, I did use an autotransformer, but, even with that, I used a 1:1 isolation transformer ahead of it, just to keep ME out of the loop. This was before GFIs.
The bottom line is that I don't have trouble with static discharge causing any problems on my layout, even the coaxial tethered throttle bus.
Point being, bypassing that isolation transformer with a wire directly to the AC ground is completely bypassing the protection provided by the isolation transformer - you have a direct wire from the high voltage side to the low voltage side of the system. There is no reason to connect your low voltage side to the high voltage side directly at all, EVER, if you use modern power supplies. Some don;e even have the ground pin on the high side, let along carry it throught he circuit.
If you need static protection - connecting the low voltage ground to the AC ground via a 1 megaohm isolation resisot is acceptable. Direct connect - no way.
It also has to do with the way the DCC signbal is generated. Digitrax swings positive and negative around the common - the pin they mislabel as ground. It's NOT ground, not in any way, shape, or form. Others like Lenz and CVP level shift the output such that the low side of the DCC waveform is the circuit ground. This is in part why it is recommended to get the special order optically ispalted boosters from Digitrax tro use a Digitrax booster with one of those systems - there's a half DCC RMS voltage differential between the two different systems, which can cause problems when a loco crosses a district powered by one to the other.
I'm guessing your static is related to the lack of humidity in the air? One website i found said mix 1/2 liter of fabric softener to 5 liters of water to make cheap anti-static spray; spray it on the carpet until it's thoroughly damp (NOT soaked) when you leave the room (so you don't walk on damp carpet).
Another site suggested adding houseplants and bowls of water around the house. I'm not crazy about bowls of water lying around but I like the idea of plants inside - I'll have to try it if static is a problem for me.
I guess you could spritz plain water around the room to add moisture (with or without fabric softener added-but the fabric softener will probably work better). If you have any scenery work to do, now might be a good time to do it (spraying the layout with wet-water will add moisture).
Fabric sheets can also be used- just rub them on whatever has static. Maybe trying to put a sheet in your shoes? or put a sheet on the floor where you frequently walk so you could 'wipe' the static off? Someone said to boil water on the stove to add humidity (adding cinnamon or citrus peels will make a boiling potpourri pot).
Many solutions but everyone seems to agree it's related to lack of humidity - fix the humidity, fix the problem.
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SEMI Free-Mo@groups.io
Pardon my naivety, but exactly how many ohms is a 1 megaohm resistor?
Thanks
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
It is 1 million (mega) ohms.
Joe