A "shocking" problem (or "static" display?)

[Kevin Strong]

So, I'm in the basement running my K-27 last night. It's trundling back and forth on my test track rather nicely, but I notice a squeak coming from the running gear when it's going backwards. Thinking it could be the valve gear, I reach my finger in to put some drag on the crosshead to see what would happen. Now, my basement is carpeted, and I was wearing socks. It's also very dry out here. You can guess how quickly static electricity builds up.

Anyway, when I went to touch the valve gear--ZAP!--. Didn't think anything of it. It's metal, and that happens. Shouldn't do any harm... Except...

First, my Aristo Revolution directional lighting which had been acting weird (being on full voltage in both directions on the forward connection terminals) all of a sudden decided to behave normally. It was now only on when the locomotive was moving forward. I can't explain it. (I moved the connections for the firebox and cab (the two lights attached to that connection) to a connection straight off the bridge rectifier that provides power to all the electronics. (The K is also wired to run off the track, hence the need for the rectifier.)

Second, my front headlight went poof! I hooked another K-27 up to my tender to check the electronic controls, they were all fine. I hooked another tender up to my locomotive, the headlight did not come on. The LED came on very dim when power was applied directly to the leads on the front circuit board, but when separated from the board, burned full--at least then. I'm betting something went weird in the transistors and all that stuff. My solution was to wire bypass that board, and wire direct to the tender connector with a dropping resistor. So, off came the shell (Thank you for making it so easy to remove!) and a new wire was run. I only had to run one wire, as the positive feed is a direct connection. Got everything hooked back up only to find that the LED was now officially DOA. Replaced that, and it's happy as a clam.

This is--I'm sure--one of those really weird freak things you read about from time to time, so I doubt we need to worry about grounding ourselves before picking up our locomotives. I haven't the vaguest clue as to what happened electronically. To say I've never had this happen before would be an understatement, but in fairness, I don't make a habit of putting my finger on metal valve gear while wearing socks and walking on pile carpet in a dry basement.

Later,

K

[rrjTooele]

Good read if nothing else. However, I live in a similar climate here in Utah. I've inadvertently scrambled a few electronics myself. I tell you what! There's nothing more exciting than to see a lightning bolt zap from your fingertip to the expensive wall control of the bedroom light in the pre-dawn hours of the morning. That was a $100 plus light show par none.

Thank you for the story. I just wish I understood half of what you were relating about the e-innards of the K.

Happy Thanksgiving!

[altterrain]

That's pretty funny Kevin! Those electrons can go odd places. Sounds like a problem for the UMD Physics dept. 

Gobble, gobble,
Brian

[NarrowMinded]

Hi,

the numbers are a simple way to estimate the voltage present at the instant of spark, it's surprising how high the voltage stored in our bodies can be at times.
mm gap  volts

0.5  2850
1     4350
2     7350
3     10350
4     13350
5     16450

Makes ya think twice about a ground wrist strap.

NM

[Joe Satnik]

Another great way to generate static electricity is to slide your "seat area" across a chair.  Ka-Zapp ! 

[Tom Lapointe]

I'll second ND's comment  about a wrist strap, Kevin.  I work in electronic manufacturing (VERY "high-end" computer equipment), & the use of wrist & heel straps (they slip over the heel of your shoes, with a band that goes around your ankle or in your sock) are a company requirement.  The wrist & heel straps also have to be tested on a daily basis (they do eventually wear out or go bad).  Modern semiconductors (transistors, IC's, LED's) operate on very low voltages and can be damaged by voltages as low as 20 volts.  When you walk across a carpeted floor, slide across a car seat, pick up a styrofoam coffee cup, or even pet your cat or dog, it is easy (especially in a dry climate) to generate static electric charges of 2000 ~ 3000 volts!   When I first started working in the electronic manufacturing field (for a totally different company than the one I currently work for), it took some time to get use to the heel / wrist strap bit; since I date back to working on vacuum tube equipment  (where normal operating voltages were typically 150 ~250 volts, (or higher!), I remembered joking to my supervisor, "You know, I can remember when I used to worry about getting shocks OUT of electronic equipment, rather than putting shocks INTO it!"                                                                                                    

                                                                                                Tom