I just fried a block power switch, my fault, I leaned on it with my elbow. Melted it big time! I'm using a MRC Tech 6 sound controller with 6 amp output. I need the 6 amps as I run a lot of lighted passenger cars and multiple locos. Is it possible to just install a simple inline fuse to protect switches or the unit itself in the event of another short? Of course, the unit is internally circuit-breaker protected, but even the manual says it's apparently not advisable to trip it too many times. If an inline fuse can be used, what amperage is recommended?
Mike C.
Wobblinwheel,
Yes You can. Install a in-line glass, fast-acting Buss fuse, a lower rating than your total output power rating on the hot side + of your system. They look like this, but there are others:
If you need 6 amps, then a lower rated fuse will not help - it will simply blow when you run that train that needs 6 amps.
Unless you run some old equipment, even a modern 12 car lighted passenger train with two sound locos pulling it shouldn't draw 6 amps.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
wobblinwheelI'm using a MRC Tech 6 sound controller with 6 amp output.
Is there a different Tech 6 with a 6 amp output other than the Tech 6 that MRC says has a maximum current rating of 2 amps? http://www.modelrectifier.com/resources/dc-ac/Tech%206%202.0%20%200001200.pdf If not, why do you want a 6 amp fuse?
This is a "Tech 6 6.0" that is rated at 6 amps. I had a Tech 6 2.0 that I now use on my staging yard, that tripped the circuit breaker every time I used lighted passenger cars and more than two locos at a time. Can't say I "need" 6 amps, but I surely need more than TWO! The switches in question are Atlas "selector" switches, which have worked fine until I aparently pushed one in an "in between" position that caused a short. This layout has been DC only for many years, and I still have a lot of old locos that will remain DC (hence the Tech 6). I've been gradually "beefing up" the wiring to more accomodate DCC, but everything has been working out pretty well. I know that 6 amps will surely find the weak spots!
wobblinwheelThis is a "Tech 6 6.0" that is rated at 6 amps.
Okay, I went and re-looked at the MRC website. I see that the Tech 6 6.0 info says that it is recommended for O and G gage in addition to Z, N, and HO and also allow one to operate up to 6 decoder equipped locos as opposed to the one that the plain Tech 6 allow. http://www.modelrectifier.com/train-controls/dc-power-tech4.asp I guess the O and G gage thing is why it has the 6 amp output rather than the original 2.
That said, it is my humble opinion that using a 6 amp fuse will only cause you trouble down the road. The usual full feature DCC system booster only puts out 5 amps. Even with that, if the railroad is broken up into blocks (or power districts) each with an electronic circuit breaker, the usual setting for those circuit breakers is less than 5 amps. Those settings are usually adjustable, but are set somewhere around 3 to 3-1/2 amps.
Even at that low a setting, it is possible to cause yourself some major grief. I have a friend who had an Atlas tank car burn down to the tracks because he had a short (I don't know if the proper term is low resistance short or high resistance short) that was not enough to trip the electronic breaker or the booster. I have another friend who had a similar short that he could not find, until someone said "what's that smell?". Turned out it was a derailed Walthers snowplow sitting on a normally unused siding. The "smell" was one of the plastic sideframes melting.
You can do what you want, but if it is requiring 6 amps to run some HO trains around I think there is some other issue.
As I tried to explain before. Put the fuse on the hot side of the power that goes to the Atlas Selector switchs rated lower than the total power output of the system. You can start with a 3 1/2 amp fast acting fuse. It will trip before your main breaker and that is what you said you wanted.
I just started playing with DC system control 64yrs ago.
Frank
I'm sure I don't have anything that "requires" 6 amps to operate, it just so happens that's what I have. The 2 amp system I had simply couldn't handle the ten lighted passenger cars (MTH "Powhattan Arrow" w/caps) and more than one or two sound locos. I think you're right that a 3.5 fast-blow fuse should keep me from burning the place down. Thanks guys for the info. This I will try.
There may be your problem - the capacitors in the cars. There is a high current inrush until they charge up. A fast blow fuse may just blow out as soon as you power the track with that train of passenger cars. It may indeed draw 6 amps, or even more, for an instant.
I agree, that is one of the reason's behind me saying start with a 3 1/2 fuse.
Why not measure the current draw with a DMM so you actually know how many amps you need.
Jim
Oh boy, you guys just opened a can of worms. The engine I use to pull these cars is the infamous Paragon (1) Class A 1218. After years of running with no problems, since I've been pulling these cars, I've been experiencing problems with BEMF (irratic speed control). Is it possible......? The CARS???
Could be either, the QSI decoder is going to have a pretty decent amount of inrush current too. Have you tried resetting it to maybe clear up the erratic running?
Instantaneous inrush current is not going to be able to be measured with a common multimeter. It's there and gone too quickly for a digital meter to respond. You MIGHT catch part of the spike with an analog meter, if it's a good one with a smooth meter movement, but even then, inertia may win out over the absolute peak.
Getting back to the Atlas selectors. After giving it some thought last nite, have not used them since the 60's, I believe the current rated caps. are not over 4amps. I tried to get the spec's, but had no luck. Even though the in-rush current, may exceed that, at times as long as it isn't constant, you should be OK, but it is something to think about.
And Randy is correct about the Meter readings. An analog meter would be the way to measure, but a gooda one. I have an old Tripplet analog that will do it.
Have Fun!
Well, we haven't used analog meters since the 80s. A good quality DMM has a analog type bar graph below the numerals. For detecting a momentary glitch it is far better than a analog meter.
Well, yeah, not quite. That bar graph is ok, but it lacks a scale, and it's still slower than a good analog meter. There are some things analog just does better. The only digital meter that will capture momentary spikes is one with a peak hold feature. And you won;t get that for $3.99 at Harbor Freight. Or even $49.95 at Radio Shack. The very expensive Fluke desktop digital meter I have doesn't even have a peak hold option. In the $100 range there are a few, with a 30ms response time. Might be enough for the capacitor inrush on sound decoders.
You can also build a circuit to do it, and then measure with any meter.
A analog bar graph has between 32 and 40 divisions for the scale. So, if you are on a 20 volt scale the middle divison is 10 volts, etc. And the update rate is 20 to 40 times a second. That's awful fast.