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Discussion Starter · #1 ·
Howdy, All

I've noticed that I sometimes short my scaley track when I run brass chasis too low or over a hump on my track. Sometimes it will sit there for a while whilst trying to "get over the hump".

Why doesn't my P/S or Controller burn up? I looked through the scaley circuit board (which I have no idea what I am looking at) and I don't see any replaceable fuses. Of course I will fix the track, but, how do I know if I am protected from shorts with the off-the-shelf tracks?

I have seen the fuses/circ breakers recommended on custom built tracks, why not the Scaley and others?

Will the current method change once the power supplies get more power for digital? Maybe I should consider an automatic, temporary circuit break for when that happens if I add a more powerful power source.

I'd hate for the place to catch fire on account of my hobby. Any thoughts?

-Maltese
 

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Brian Ferguson
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3,652 Posts
Maltese, the standard set power supplies are forgiving, oddly enough because they are poor supplies to begin with! Some have short-circuit protection built in, but most don't. During a short, the voltage drops to near zero and the amperage is insufficent to cause major problems - although shorts of long duration can kill the supply itself.

Good regulated supplies, or worse yet, batteries, put out enough current to become miniature arc welders and need proper fusing to guard against short circuits. Most good supplies will have such protection built-in but I still like to fuse each lane separately, at a value lower than the supply's own protection, just to be extra safe and to aid in determining the source of a short.

If you upgrade your power source, be sure it is protected and give serious thought to adding additional protection, by lane.
 

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Discussion Starter · #4 ·
I appreciate the help. You have no idea how much!

So, if I have a 6AMP power supply a fuse per lane should be approx 2Amps?
Total guess.

Thanks

-Maltese
 

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Brian Ferguson
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It depends on the cars you intend to run. For basic, out-of-the-box cars, I would probably fuse the lanes at 2-3 amps. This will protect against dead shorts. For cars with hotter motors, like a Fox or Little Ripper, more like 3-4 amps. If you play with Falcons or TSRF type motors, then go to 4 or even 5 amps. I'm assuming the 6-amp supply has its own fuse too. If it doesn't, I'd add a primary one rated at 6 to 8 amps (good power supplies have a surge current considerably above their nominal rating).

If you fuse the lanes too low, you can get false fuse triggers by very brief shorts. Fuse too high, and you defeat the purpose.

The goal, really, is to fuse the lanes higher than the anticipated maximum motor current draw in near-stall situations, yet low enough that fuses will blow fairly quickly in dead-short conditions. And always lower than the power supply's max rated surge output, preferably much lower.

Fuses, however, are cheap, so finding a good value for your own situation is not difficult. Start low, and increase until you don't get blown fuses during normal running of cars you know are in good shape. Then add 1/2 to 1 amp to avoid nuisance triggers by very brief shorts (which all slot cars can do, particularly as they deslot). The resulting value, if lower than the supply's rating, will give you good protection and prevent problems from full short situations.

My supply puts out 6 amps per individual lane (8 amps surge) and I have always fused lanes at 4 to 5 amps each on various types of tracks, from plastic to taped wood. Never had a problem, and only a rare serious short has ever blown a fuse yet I've never had track damage either.

Hope this helps a little.
 

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Discussion Starter · #6 ·
You have helped a billion! Thank you VERY much.

I will apply what I have learned.


-Maltese
 

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I know a club which keeps two truck batteries wired up to some open ended wire. When ever they get a short they cut the track power, remove the car and place the wires across the rails (braid actually). You see a bit of a spark somewhere around the track and it is blasted out of the way!

It's a little extreme IMO, but I suppose it beats walking round and looking in the slot...

Just a little side note.

LMP: good idea with the tape


Lotus
 
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