Help With Shorting Problem

[Bill54]

As Randy has suggested, The next time the problem arises I will hook up the 1.2 amp 12V wall wart and see what happens.

Thank you all for your suggestions I really appreciate all the help.

Bill

[richg1998]

 I would try a different power pack, wall wart. At least 1 amp, maybe more,  capability.

Rich

[rrinker]

 My thoughts exactly upon reading that. Just how are you checking for a 'short'?

If all 18 LEDs are lit at the same time, plus 4 Tortoises..with 750 ohm resistors, that's pushing just slightly over 300ma depending on who's rating of the Tortoise you believe, so I suspect the power supply is overlaoded and won't start until you remove some of the load by disconnecting the Torti. Try the 1.1 amp power supply, it won't hurt anything, plus you'll be able to add even more LEDs and Tortoises.

                       --Randy

 

[jeffrey-wimberly]

 If you're using the multi-meter to check for continuity it will show a short when the tortoises are connected as the motor(s) complete the loop. It's like trying to check your track for a short when there's a loco on it.

[Bill54]

I think I used 750 OHM resistors on the LED's.  All 18 are lit at the same time along with the four tortoise machines.The first time this happened I did use my multi meter to check for a short and it showed a short until I disconnected all the tortoise machines.  Then it showed no short.  As soon as I hooked up the first tortoise machine the multi meter showed a short again.  However, everything worked.  I think the tortoise machines complete the circuit and will show up as a short.  However, when the problem occurs nothing works until the 10 pin connectors are removed and replaced.

I do have a fiberglass spacer on the eighth slot so the 10 pin connectors align properly with the eight connections on the tortoise.

Let me explain how I have the LED’s and the tortoise machines hooked up.I connected the wall wart's positive and negative polls to two Radio Shack eight poll power strips.  One strip is negative one is positive.The eight LED's used for the staging tracks are connected to one pole each VIA 4pole double throw toggle switches.  I used 4PDT switches because I am using DCC and the LED's require DC current.  The 4 polls allow me to use two for the DCC current and separately use the other two for DC current to the LED's.

The four tortoise machines are connected separately to the power strip VIA DPDT toggle switches.  The LED’s for the tortoise machines are connected to the toggle switches and are bipolar LED’s that change from red to green and back. 

The layout is in my finished basement that is climate controlled.  So I don’t think the problem is corrosion.  And if it were corrosion I would think I would still have power going to the eight LED's that are being used on the staging tracks.  But they do not work until I disconnect and reconnect the tortoise machines.It looks like I'll have to wait for a month or so and try it again.  Should it happen again I'll try replacing the wall wart with a higher amperage wall wart.  I have a 12V 1.2A that I recently purchased.  That should power all my LED's and tortoise machines.I appreciate everyone's help so far.   And will keep you up to date on this problem. 

Bill

 

[mfm37]

I'm with Jeffrey on this. Corrosion at the plugs causing no connection. Not a short, just no connection at all.

Each time the plugs are pulled and reinserted , the corrosion wipes off. Clean them with contact cleaner and perhaps carefully apply a coating like Atlas Conductalube or CRC 2-26. That should slow or stop the corrosion process.

 Martin Myers

[rrinker]

 There aren't any capacitors in a Tortoise. It's a very free-spinning, low current motor plus a lot of gears.

 back to the original - how many total LEDs are lit at any given time, and how many total Tortoises are there? What size resistors did you use with the LEDs (to get an idea of just how much current is flowing in each LED)? You MIGHT be exceeding 300ma, but I doubt it. But keep in mind that depending on the resistor used, a typical red/green/yellow LED will draw around 15ma - actually MORE than a Tortoise. So 300ma is any combination of about 20 LEDs or about 30 Tortoises or some combination thereof.

edit: ok, 8 LEDs for track status plus 10 on Tortoises, which means probably 5 lit at any given time (since the Tortoise can't be both normal and diverging at the same time ), plus 4 Tortoises. If all 8 track LEDs are lit, plus 5 route LEDs, that's 13 x 15ma plus another 40ma for the Tortoises, 235ma, so it should be fine. If you have a slightly smaller resistor the LEDs could be being driven closer to their max of 20-25ma, if it's 20ma then you are right at 300ma. The 10ma rating of the Tortoise is more or less an average, I've seen them listed at 18ma stall.

 In short (ha ha) it may be that you are simply overloading the 300ma power supply.

                --Randy

 

[mavrick0]

I would be looking that transformer itself.  Doesn't sound like a short.  What it sounds like is after sitting a while all the capacitors in the Tortoises drain to zero and when you try to power it up the high inrush from the caps wanting to charge either shuts down the transformer and goes into overload protection or will just take a while to come up to normal voltage.  When you unplug the few tortoises it chargers the one, turns on the LED's then you plug in the others one by one which the short time between plugging each one in charges the cap quick enough to not cause a problem by the time you plug in the next one.  Then of course the caps are charged and don't cause you this problem until a few weeks later and they again have dropped to zero voltage.

[jeffrey-wimberly]

how can you explain it working just fine when I turn on the power strip the next day or within the folowing week.  It will work fine.  It's only when I wait a long time like I said a month or longer for it to act like a short.

It doesn't take that long for enough corrosion to build in the joint to break contact. If the circuit was live 24/7 it would take longer but it would still happen.

[gandydancer19]

One thing that you can do with your 10 pin tortoise connectors is to make a plastic shim or insert to go in both ends of the connector to force the connector to be centered on the tortoise.  Once you get them the right size they can be glued in the connector.  .125 x .125 x .040 or .060 evergreen comes to mind, as that is what I do.

[larak]

Bill,

You should troubleshoot the next time there is no power

1) See if the adapter is live - it could be loose in the power strip. You should hear and feel it hum slightly and it should be warm but not hot.

2) Remove one edge connector at a time and recheck the power. 

3) the adapter could have an intermittant connection that opens when it gets too hot.

4) A voltmeter or test light would be helpful.

Perhaps moving the edge connectors is making some other connection move and make/break

Edge connectors can move with vibration too.

You might want to hookup a "pilot light" or resistor/LED across the adapter output near the adapter to see just where you are losing power. A meter would still be more useful though.

Karl

 

[Bill54]

rrinker, 

I am using the 10 pin connector.  However how can you explain it working just fine when I turn on the power strip the next day or within the folowing week.  It will work fine.  It's only when I wait a long time like I said a month or longer for it to act like a short. 

Something I didn't mention in the first post is the power supply.  It is a 12V 300 mah wall wart that came from our former cell  phones.

I don't want to have to solder the connections straigt to the tortoise unless it is the last opportunitity I have.  Other connections I have made with the same connector are working flawelessly.  Not to say that one of the ones I have hooked to one of the three tortoise that are giving me problems are the problem child.

Biggest question is why is it only after a long period of time. 

All day todayn I have been turning the power on and it is working properly. 

Can anyone explain?  I'm confused and frustrated!!!!

Thanks,

Bill 

[rrinker]

 Are you using the proper 8-position conenctors for the Tortoises or standard 10 pin ones? If you aren't careful with the 10 pin ones you can offset them a little and they will touch the wrong terminals on the Tortoise edge connector and cause a short. There are two ways I see of handling the Tortoise (3 if you count just soldering the wires right to it - since I've never seen a Tortoise fail this might not be all that impractical). One is to solder short lengths of wire to the Tortoise and run them to a terminal strip, to which you then connect the wires leading to the control panel and LEDs. You cna make these up ahead of time, before installing the Tortoise. The other alternative is to use pins and connectors commonly called 'molex' connectors. There are straight and right-angle pins you can solder to the Tortoise - your control panel wires go to sockets that fit inside a plastic shell, this slips on and off the pins on the Tortoise so you can easily disconnect it and remove it if required.

 

                                     --Randy

 

[jeffrey-wimberly]

You have a bad connection. Somewhere there's a place where the wires aren't making as good contact as they need to be making. This is why I solder ALL connections, be they wire or rail. Don't trust slip-on connectors even if they are tight. Murphy needs only a very tiny gap to start laughing at you.

[Bill54]

I think I'm having a problem with my tortoise machines shorting.  Let me explain.

I have four tortoise machines hooked up to one wall wart.  The wall wart also powers 18 LED's.  Eight of the LED's are used on my staging area to show which track is turned on and which is turned off.  The other 10 LED's are connected to the tortoise machines.  They are used to show whether the train will use the diverging or main track.

I have the wall wart connected to a power strip so all I need to do is turn on the strip and my electrical equipment all comes on at one time.

The problem I'm having is when I leave the system turned off for a long period of time, say several weeks, then turn the power back on, none of the LED's work nor do the tortoise machines work.

One tortoise is hard wired and the other three I used a connectors that slide over the end of the tortoise electrical boards.

This problem has happened two times.  The first time I thought I had a set of wires shorting but they really didn't look like they were touching.  That first time I removed the connectors from the three tortoise machines and simply replaced them. 

When I turned the power strip on everything worked fine. 

Since that day which was about a month ago or maybe longer I have  been working on laying more roadbed and track.  I haven't done any work on the wiring that goes to the tortoise machines or the LED's. 

Last night I turned the power strip on and again none of the LED's came on and again the tortoise machines did not work.

Today I disconnect the connectors from the three tortoise machines, turned the power strip on and all my LED's  lit up.  

I turned the power strip off, reconnected the connectors to the tortoise machines, then turned the power strip on and everything works again.

Now you can turn the power on and off all you want and everything works.

Is there any idea why when the power stays off for a long period of time the tortoise machines seem to short until I disconnect them and reconnect them?

I'm wondering what I'm doing wrong or do I need to rewire so that the LED's that I'm using for the staging area are separate from the tortoise switches?  Or should that make a difference anyway?

Thanks for any help.  

Bill