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DCC Block Fuse

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  • Member since
    April 2009
  • From: Granger IN
  • 265 posts
DCC Block Fuse
Posted by Dannyboy6 on Monday, May 1, 2017 9:35 AM

Good Morning,

I just noticed this product in the current MR. It claims to be block short circuit protection for $5 per block, less in bulk. I'd like to know how others view this product.

http://voltscooter.com/?page_id=134

Dan

  • Member since
    July 2009
  • From: lavale, md
  • 4,678 posts
Posted by gregc on Monday, May 1, 2017 10:23 AM

shorts are very likely every time metal wheels derail.   Not sure what they mean by easily reset.   Don't most DCC circuit breakers automatically reset?  

I use light bulbs.  let you know when there is a short or high load and clear as soon as the load drops.

greg - Philadelphia & Reading / Reading

  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Monday, May 1, 2017 10:37 AM

Looks like it is just an array of PTC fuses = positive temperature coefficient resistors, or one common name brand "polyfuse".

Will it work? Should. But not a chance it is fast enough to open one section where a short has occurred while keeping a different section operational. PTC fuses are slow, most any command station would trip long before the PTC fuse would.

                         --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    October 2002
  • From: City of Québec,Canada
  • 1,258 posts
Posted by Jacktal on Tuesday, May 2, 2017 10:15 AM

Light bulbs aren't fuses.They use the short as a switch to turn on and thus maintain a load equivalent to the bulb's draw on the shorted spot.The typically used automotive 1156 draws two amps wich is more than enough to fry many decoders should the short occur in the loco's motor or one of the decoder's functions.

Given,they're harmless if the short is limited to the tracks and are useful to identify the shorted area but in no way are as safe as breakers for decoders.Their protective feature is an illusion.Don't let trains run unattended.

  • Member since
    July 2009
  • From: lavale, md
  • 4,678 posts
Posted by gregc on Tuesday, May 2, 2017 11:54 AM

Jacktal
The typically used automotive 1156 draws two amps wich is more than enough to fry many decoders should the short occur in the loco's motor or one of the decoder's functions.

the short caused by a derailed car or a metal object across the track is not through the decoder, it's across the output of the throttle.    A lamp limits the current drawn from the throttle which not only protects it, but in my case, a PowerCab, prevents it from shutting down which takes ~10 secs for it to restart to determine if the short is still present.

There is no worry that a train derailment is going to short through the decoder.  The short is across the rails and prevents power from reaching the decoder.

 

A fuse is less expensive device that fails in order to protect a more expensive device.   A fuse requires replacement.   As I said intially, shorts are common on model railroads.   I don't want a fuse, I want a device to limit the current to what a throttle is designed operate at, both so that it does not get damaged or shuts down.

this is why I use lamps, and considering that the latest MR magazine has an article on using them, why others use them as well.

 

if you want to protect the decoder due to a short in the motor, some type of protection device is needed in the locomotive or decoder to limit the current the decoder is restricted to, not between the track and a throttle which may have sufficient power (e.g. 10A) to drive many locomotives.

greg - Philadelphia & Reading / Reading

  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Tuesday, May 2, 2017 4:20 PM

 Not all shorts are between metal wheels of unpowered cars - in fact mainly only those that happen when backing the train so the caboose derails first. If the loco derails first, that short isn;t through the decoder and motor (unless the motor is not properly isolated, but that's another story) but it can easily be between the piece of wire on a wired decoder or a thing PCB trace on a board replacement decoder - the wire or trace connecting the front truck to the rear truck on the same side. Might be ok with 2.1 or 2.5 amps going through it continuously. I still say an electronic or at least electromechanical breaker that actually removes power is much better. My PM42 has never had a problem AND I have not had problems with it restoring power even with a bunch of sound locos in the same section. No idea why some people have trouble with this.

 This new cheap product is just some resettable polyfuses. It's not a one shot deal. I question if you really get the current multiplication effect with multiples in series/parallel - the 'jumpers' it has are 0 ohm resistors bypassing each polyfuse past the first one - but removing each 'jumper' you put more polyfuses in the circuit for a greater amp capacity before it opens. I guess if you goof you can solder bridge the pads to restore the jumper.

                             --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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