Using NCE power cab. Running 3 locos. 2 Atlas gold & 1 Broadway Ltd, both with QSI sound/DCC decoders.
I usually run the locos at a scale speed of 50 MPH as reported by the QSI sound. [Top speed of 72-82 MPH.] Before installing the 1156 bulb, track voltage with no load was 19.9 VAC. With all 3 locos at full throttle, current draw, as reported by built in meter on the Power Cab, was approx. 1.46 Amps.
After installing a single 1156 bulb in series with one side of track feed the no load AC voltage remained at 19.9 VAC. However, with the 1156 wired into the track feed, and all 3 locos at full throttle, top speed is reduced to 42 MPH, as reported by QSI decoder. Current draw with all 3 locos at top speed is approx. 1 amp. Bulb glows at a medium level.
The 1156 may be an excellent short circuit protection solution on larger higher power DCC systems where only 1 or 2 locos are in a block protected by an 1156. In my situation, where I am feeding all power to the layout through 1 bulb, it seems that the bulb is sucking too much of the power for use with a lower AMP power cab?
I need to come up with a different short circuit protection solution. Currently, if I get a short, usually caused by a derailment on a turnout, I immediately shut off the power.
An easy fix would be to put a second bulb parallel to the first. The trick is the current level at which the bulb starts to become active. I'd have to go back and check the numbers, but you are obviously pushing it a bit, since the bulb is glowing. With two bulbs in parallel, you could draw twice the current before they kick in.
Jeff But it's a dry heat!
Jeff:
Great idea, in fact I had to buy 2 of the 1156 bulbs in a blister pack anyway, so I have an extra bulb. I won't get a chance to try this until tomorrow or Monday. I'll put a post on this thread to let you and any other readers interested know how it works out.
The light bulb trick was originally designed to be used in place of additional circuit breakers to divide a layout into zones or power districts (such as the PS4 that Tony's made and sold). If you have a small layout, and operate alone, you don't need them. Your DCC system was designed with a good fast acting circuit breaker in it. If you have a garage size layout, you can use the bulbs to divide the layout in to zones or power districts.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
I am not by any means an expert in DCC, but my understanding so far is that anything over about 17 volts in HO is too high. Your system sounds like it is operating as it would if you were in O scale. My digitrax DB150 has a three way toggle to select scale output. I inadvertently filpped it up to the O scale setting one time when I was going by feel and thought I had flipped up the power toggle. Who knows how long it was before I found the need to check track voltage, but I darned near had a cow when I saw it over 19 volts. I looked, and sure enough the scale toggle was set on O. I feel that this may account, at least in part, for your light bulb not working. I have my small layout broken into four districts, but not power districts. Instead, for short management, I had four sub-buses with a single 1156 bulb wired in series into one of the two wires comprising each sub-bus. They work marvelously, no warmth, no glow, and my engines will haul their substantial trains up my 3% grades any time I make them....so rail power is not an issue.
Something to think about?
-Crandell
The bulb element glows faint. Normal. 2.1A thru the bulb is full on. The more current = more heat = higher resistance. So this is all normal. But then I don't understand why run the whole layout thru ONE bulb. Might as well let the Power Cab stop the short period in this case. But suspect it has to do with having to unplug the Power Cab to recover from a short. You'd be better served having multyple blocks protected by multyple 1156's seems to me.
RRCirkits has a nice writeup using 2057 bulb and a PTC fuse of 0.9A that makes this type of short protection safer to use.
Also found this doc. http://www.members.optusnet.com.au/nswmn/1156.htm It talks about your three loco issue and fixes.
I've got an NCE powercab too and I use a circuit breaker purchased from Tonys train exchange.
http://www.tonystrains.com/products/dccspecialties.htm
Its a PSX DCC circuit breaker. I know its $34.95, but I think well worth it. It resets immediately after the tripped circuit as opposed to the NCE internal circuit breaker which takes 12 seconds and has to reset the whole thing.
selector wrote: I am not by any means an expert in DCC, but my understanding so far is that anything over about 17 volts in HO is too high. Your system sounds like it is operating as it would if you were in O scale. My digitrax DB150 has a three way toggle to select scale output. I inadvertently filpped it up to the O scale setting one time when I was going by feel and thought I had flipped up the power toggle. Who knows how long it was before I found the need to check track voltage, but I darned near had a cow when I saw it over 19 volts. I looked, and sure enough the scale toggle was set on O. I feel that this may account, at least in part, for your light bulb not working. I have my small layout broken into four districts, but not power districts. Instead, for short management, I had four sub-buses with a single 1156 bulb wired in series into one of the two wires comprising each sub-bus. They work marvelously, no warmth, no glow, and my engines will haul their substantial trains up my 3% grades any time I make them....so rail power is not an issue. Something to think about?-Crandell
That voltage is correct for an NCE powercab. Mine is the same.
Thanks for the confirmation, Driline. I'll file that away as useful info for future use.
betamax wrote:Actually, this is not a good idea.You are in fact interfering with the operation of the short circuit protection circuit. Additional resistance will defeat the purpose by not letting it see a sudden increase in current flow, which would indicate a short.That is why wiring for DCC is always a lot heavier, because voltage drops may in fact prevent the short circuit protector from operating, and by the time you realize what happened, it is too late.
Yes and no! In this instance, using the bulb to protect the layout doesn't make a lot of sense. In the "normal" case, you use the bulbs to divide the layout into smaller pieces. you want the bulb to stop the command station from seeing the short circuit so that the rest of the layout can continue to function. With a PowerCab or Zephyer, this might not make a lot of sense, as the bulb will be drawing around 2 Amps, so there's not much left for the rest of the layout anyway. Since most of the voltage will be dropped across the bulb, the current to the short itself is limited, in theory preventing damage.
Yes, using one bulb to "protect" an entire layout is not a good idea. The current limit on a single bulb is just too low.
The basic idea is to subdivide the layout up into train-length blocks and then protect *each* block with a bulb. The beauty of the technique is when cold, the bulb has near zero resistance, almost like it's not even in the circuit -- but when a short occurs, the bulb suddenly becomes the load in the circuit, limiting the current through the short to no more than the bulb's current limit -- which is 2.1 amps in the case of an 1156 bulb.
The bulb becoming the load also makes the short simply look to a power booster like several locos suddenly were put on the track -- and it does not register as a short at the booster. This means other trains in other train blocks in that same booster district will keep on running, and gone are the cries of "hey, who shorted the layout!"
I demonstrate this all on video here.
You can also mix and match various bulb combinations to get the specific current limit that works for your situation. I also discuss how to do this at the video link above.
I've had the bulbs in place on my HO Siskiyou Line since 2000 (wow, 8 years now) ... and they work like a charm. My operating crew doesn't even know where the booster power districts are any more because only the guy who gets a short quits running. Before 2000, believe me, all of my operators were all painfully aware of the booster power district bondaries whenever someone shorted the track by accident (sometimes several times a session).
Joe Fugate Modeling the 1980s SP Siskiyou Line in southern Oregon
steamnut wrote:I, too, have a Powercab, purchased about six months ago. How do you access the built-in meter that you reference?
steamnut,
To activate the built-in ammeter in your Power Cab, perform the following sequence:
The ammeter replaces the fast clock display in the upper right corner of the LCD screen. Once you turn off your Power Cab though, the ammeter resorts back to the fast clock display the next time you turn your Power Cab on again. This feature also doesn't work when the Power Cab is used in conjunction with a Smart Booster.
Hope that helps...
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Re: Built in Power Cab Amp meter.
On my cab, ver 1.28B, the meter replaces the clock in the LCD, and can be accessed as with the following key sequence:SHIFT+61PROG/ESC
Contrary to previous statement, shutting down and restarting my power cab does not turn off the meter.
The meter can be turned off as follows:SHIFT+60PROG/ESC
Re the 1156 bulb as short protection dialog. In my situation, seems opinions vary from, Not needed; actually a bad idea; to use a $35 PSX DCC circuit breaker! For sure, a single 1156 does not work, 2 in parallel is probably to high a current limit for the power cab. I'm going to look into the PSX breaker. Thanks for all the responses.
Good, Don, just checking to make sure you were truly oriented. It sounds like you have a good understanding of what needs to be done, particularly in view of the large numbers of working engines you are likely to have placed in any one of the powered sections. You may find that you need one of those devices in each of them, except for any powered directly by the base station.
djb39 wrote:I understand, but, my RR is not large. Two ft. wide shelf around an area of 13X8. Approx. 85 ft. of main line in a double loop with an over/under grade, including passing sidings. It is already divided into 3 power zones, each zone insulated from any others and wired back to the single DCC Power Cab. Due to the small size and track plan, there would without a doubt be times when all l3 ocos [1-2 loco consist, 1 single loco] would be in the same zone, causing a slowdowndue to current draw.
Then it would seem for the ligh bulb method to be really effective you need smaller zones. And really a bigger booster. As it is now, a short that causes the lights to light is going to draw about what the PowerCab can put out anyway, so there won't be enough juice for the rest of the layout anyway. In this case, getting rid of the bulbs altogether, and letting the PowerCab do the protecting might make as much sense as anything.
selector wrote: Good, Don, just checking to make sure you were truly oriented. It sounds like you have a good understanding of what needs to be done, particularly in view of the large numbers of working engines you are likely to have placed in any one of the powered sections. You may find that you need one of those devices in each of them, except for any powered directly by the base station.-Crandell
I invited Don over to my house where he was able to see first hand my NCE powercab, autoswitch, and PSX circuit breaker. My layout is similar in size to Don's. I find one PSX circuit breaker sufficient for a layout my size. It also allows for LED monitoring of power and short circuits from an easy to see panel on the fascia of the layout.
I wish I could use those bulbs, they seem an inexpensive alternative. But 35 bucks is worth the piece of mind to me knowing the circuit breaker takes the short circuit and not my powercab. And the fact I don't have to wait 12 seconds (an eternity) for the powercab to reset after a short.
My small 11X7 layout..
In the "Manual" that comes with the Smart Booster (SB3) NCE recommends using the #1156 tail light bulbs for short circuit protection. They even provide an illustration showing the wiring. I bought the Fugate DVD before I got my Power Cab, cut my layout into 4 power districts (each protected by a #1156) and it all works perfectly.
OldStone, O & W Rwy