Recycled electrons

[MarkSG]

I've been working on the underside of the layout this afternoon, completely rewiring the point motors after reaching the conclusion that telephone cable, while it seemed a good idea at the time, really isn't suitable.

 

Anyway, I started off by connecting up the common returns as a loop, then added the switch wires to the first motor. Connected them up to the PCU, flipped a lever to test it and "click" - the point threw, exactly as expected. Good start, I thought. Flipped the lever again, just for the sake of it really, and nothing happened. Toggled it a few times, still nothing. Grr.

 

My initial thought was that either I'd simply caught a wire somewhere on myself as I was moving (since nothing is tidied up yet, it's all hanging loose, I'll wrap it in cable ties when all the motors are connected) and disconnected it, or even that the motion of the motor the first time had caused a badly made connection to work loose.

 

So I went back over all the wires, checking every connection. No visible problems found. I don't, unfortunately, have a working multimeter at the moment, so to try to narrow down the problem I added a second common return to the first point motor, bypassing the loop. Still nothing.

 

Was it, possibly, a faulty motor? I connected switch wires to the second motor and tried that. Still nothing. Maybe the PCU, then? But it's new, only bought a couple of weeks ago, so it's very unlikely to be faulty. Maybe check the fuse, and the plug, and....

 

D'oh.

 

It wasn't plugged in at all. The power cable was simply draped across the workbench, nowhere near a socket. Plugged it in, and all is fine. Of course.

 

I can only assume that the capacitor had enough residual charge from the last time it had been plugged in to throw a point, just once, even after being unused for more than a week. People who know more about these things may not be surprised by that, but I was. It was certainly enough to completely throw me off the scent when trying to track down the initial problem (because, of course, if nothing had happened the very first time I flipped the lever, the first thing I would have checked is that it was plugged in). As it was, I was close to tearing my hair out before my unexpected epiphany.

 

Anyone else had a similar experience where you've completely missed the most obvious solution to a problem because of something that threw you off the track like that?

[rodshaw]

I made a loco which kept intermittently causing a short and stopping over live frog turnouts when going slow. I checked everything (or so I thought) - wiring ok, wheels not in contact with the wrong polarity point blades - then eventually I realised the gear wheel on the driven axle, being quite big (about as big as the driving wheels), was occasionally just touching a switchblade when passing over it.

[Kenton]

Plenty, unfortunately none that I remember which is probably why they keep surprising me

[kevinlms]

There is a simple way of preventing this, as it can cause problems - such as going to solder something & create a path. While it won't kill you, the surprise might make you bump your head or such.

 

Wire an LED (with suitable resistor - make it quite high value 10K or so, the value depends on the supply voltage) across the output. The LED will cause the capacitor to discharge once the power has been turned off & still give you an indication if power is available to use.

 

Kevin Martin

[Barry Ten]

 

 

I can only assume that the capacitor had enough residual charge from the last time it had been plugged in to throw a point

 

 

That one's caught me out many times. Capacitors can hold enough charge to throw a point for months, too, as I know from

Paynestown and Cogirep. When I take either one out of storage, there's normally enough juice to throw a point.

[Southernman46]

That's exactly the reason we earth the OLE before physically getting close to or working on it, despite the current being off there can be enough residual charge left in the wires to cause serious injury and certainly surprise (which is not good when you're 16ft up).

[mwrosebury2000]

I had a similar experience with a strobe out of an alarm box… made me jump.

 

The one I forget especially when using phone cable is forgetting to label them… I have had to rewire more than once when I haven’t be able (or bothered) to trace a faulty cable across the layout.

 

Although yes I have been pulling my hair out when it hasn’t even been plugged in, thought I was the only one.

Mark