Hello everybody,
We have had two oddball electrical occurances at the club in the last two weeks that have left us scratching our heads.
The first one involved a track power circuit breaker that was clicking in and out. There was no activity on the layout and, in fact, the track power wasn't even turned on. It started clicking out of the blue and continued for several minutes. We turned everything off, and when the power was turned back on it resumed clicking. Then we turned the track power on and off a couple of times but the problem persisted. A couple of minutes later, with the track power off, the clicking stopped all on its own. I know you are going to ask me what the exact device was but I'm not sure. I will ask our master electrician tomorrow and get back to you.
The second problem involved several tortoises that would operate fine when thrown in one direction but move very slowly in the opposite direction. These tortoises are all on the same control panel and they happen to be the last six tortoises in the series of 15 switches. We are using a dual power supply system with +12 volts on one side and -12 volts on the other. The power supply is daisy chained to each of the switches so the power is not running through one toggle switch to get to the next one. The slow speed occurs on the + side in all cases. All tortoises had been operating properly up until this time.
So far we have tried the following:
- We used jumper wires to bypass the + feeders so that the power went directly from the incoming power bus to each of the slower switches. That made no difference. We did not try disconnecting the first tortoises in the series so all the tortoises were still drawing power. (I suppose that is what we should try next).
- We tried attaching the tortoise feed wire to a switch that was working properly. No difference.
At that point we decided to quit for the night.
Could this be a problem with the +12 volt side of the power supply? The supply is nowhere near its maximum capacity in terms of the number of tortoises that it is feeding. If the supply is not putting out what it is supposed to (i.e. it is now overloaded), would it affect the last tortoises in the row instead of all of them?
Further details: Some of the tortoises have 2 LEDs in series with the feed to the tortoises. Those do not have any resistors. The tortoises that do not have LEDs in series have 220 ohm reistors in series to reduce the power going to the tortoise motors. The LEDs connected to the slow tortoises are quite dim when the tortioses are moving slowly, and have normal brightness when the tortoises are moving at the proper speed.
The more I write the more I suspect the +12 volt power supply.
Thanks for your help.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Dave,
No opinion on the first item. Power supply - I would suspect the 12+ leg of the power supply. Check it with a meter to determine amp draw on the circuit as well as voltage reading. You could have a short or other heavy load on the + side of the supply or it could be a bad transformer/part in the supply itself. I have used bipolar busses for years. This is a common problem when the power supply is fried.
I quit using cheap, unregulated wall warts for my supplies when I encountered this problem years ago. No problems since I installed high quality switching supplies.
Guy
see stuff at: the Willoughby Line Site
Have you tried swapping the plus and minus feeds? It should make the machines backwards, but test your power supply hypothesis.
Has this ever worked properly? I'm wonder if the Tortoise wire is running into the sides of the hole.
It takes an iron man to play with a toy iron horse.
The tortoise problem has been solved! Our Master Electrician was under the layout measuring the power on all of the tortoises when he came across a yellow wire that was dangling all by itself. The yellow is the common for the tortoise motor feeds, Once the wire was put back where it belonged everything worked fine! However, we are at a loss to explain how one common wire disconnected from one tortoise would cause the issues we were experiencing.
The circuit breaker that was clicking in and out was a Digitrax PM42. It hasn't happened since so for now we will use the 'cross your fingers and hope' method of repair. Until it happens again there's not much else we can do.
Perhaps the power supply for the PM42 wasn't plugged in, it will tend to keep clicking.
The problem with the Torises is that if the common for the +/- power supply wasn't connected, they STILL could reference the other side of the pwoer suppyl circuit through the + or - of the other Tortoises - seeing 24 volts but through a LOT resistors (the Tortoise motors - plus the drops of the diodes in series) so they were probably getting under 6 volts when all was said and done. And moving very slowly. That common reference is pretty important, so that the Tortoise sees 12 volts with either pin 1 +12 relative to pin 8, or pin 8 +12 relative to pin 1.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker Perhaps the power supply for the PM42 wasn't plugged in, it will tend to keep clicking. The problem with the Torises is that if the common for the +/- power supply wasn't connected, they STILL could reference the other side of the pwoer suppyl circuit through the + or - of the other Tortoises - seeing 24 volts but through a LOT resistors (the Tortoise motors - plus the drops of the diodes in series) so they were probably getting under 6 volts when all was said and done. And moving very slowly. That common reference is pretty important, so that the Tortoise sees 12 volts with either pin 1 +12 relative to pin 8, or pin 8 +12 relative to pin 1. --Randy
Once again Randy to the rescue!!!
Thank you for explaining the likely cause for the PM42, and why the Tortoises still operated.
In the electrical business a disconnected return is known as a loose or hot neutral. Particularly in 240 volt panels with two or more 120 volt busses, an open neutral will cause voltage from one leg or phase, not finding the usual return, to seek a return through the other leg, forcing double voltage, 240 volts, through the both 120 volt circuits. In your case apply the analogy to multiple 12+ volt sources with a broken 12- return.
If the load on both circuits is by chance balanced, you just got lucky. If not, everything on the lesser load gets fried. I've seen entire labs of electronic equipment go poof because of a loose neutral connection at the university I worked in as an electrical troubleshooter. Kudos to your sparky for finding the problem. -Rob
Hi Rob,
Mister MikadoIf the load on both circuits is by chance balanced, you just got lucky. If not, everything on the lesser load gets fried.
I guess we were lucky.
The Tortoises normally see about 8v because there are either two LEDs or one 220 ohm resistor in series with the 12v motor supply lines. Does that mean that we were actually feeding 16v through the circuit?
I'll suggest that we go over all of the connections to make sure everything is tight.
Thanks,
Dave - with the 12 volt common return broken, one 12 volt supply line was trying to return to the transformer through the other line, assuming your power supply was set up like the pot transformer you see mounted up on a utility pole outside. Then all the tortoises were in the path of 24 volts, but that doesn't mean they felt all 24. The tortoises, LEDS and resistors broke the voltage down according to their amp draw. Since the return line was hanging free, you had a relatively predictable and safe incident. At my job, a corroded buss would cause a wild state of resistance across the neutral prong of an entire electrical panel. The double voltage had dozens of circuits with varying loads to prey on and raise havoc with, delighting in frying lighter load circuits every time the neutral cut out, because the corrosion made its own constantly changing resistance.
If nothing smoked, consider it a lucky break! -Rob
Mister MikadoIf nothing smoked, consider it a lucky break! -Rob
Thanks for taking the time to explain the situation Rob.