I don't know of any that DON'T do that. The excess heat is in the booster, not the cabs though. The booster typically uses an H bridge to drive the track output with the peak set by whatever mechanism, a control from the processor or a potentiometer, usually with a voltage regulator circuit.
There's nothing else to blow the excess voltage as - it can;t just go into space, that violates the laws of conservation of energy. No matter how you drop voltage - a regulator, a resistor, a light bulb, diodes - the excess comes off as heat.
Decoders don't drop the voltage at all (well, they usually have a regualtor to drive the processor, but that's a miniscule amount of current). The voltage to the motor is fed by an H bridge that runs nearly rail to rail - however it is pulse width modulated so the effective voltage the motor sees varies depending on the speed being commanded, which changes the width of the pulse. At half throttle, the pulse is at about 50% duty cycle, which results in an effective 50% of the voltage being delivered to the motor. There is little heat in such a design, which is why a tiny little decoder can handle more than 1 amp loads. But that is merely switchign the supply (track voltage) - the pulse peaks are approximately the track voltage. To get the track voltage at some level, the booster has to limit the voltage, in a more traditional manner. So if you use a 20V power supply but set the output voltage to be 12V, you have to waste that extra somewhere, and it's ALWAYS heat.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
DigitalGriffinI agree. Typically most circuits will transform any reduction in voltage (through a voltage regulator) into heat. In other words, the bigger the difference between input and output voltage, the more heat you will generate. If that voltage correction is done in the cab, that cab will get hotter reducing their lifetime. I would try to find a power supply closer to what you need. Or build a custom adjustable one like I did using a 18Volt laptop power supply
If a DCC decoder operates like that, I would be very disappointed at the brand that made it. There are efficient ways to drop voltage without blowing the entire difference off as heat. It's easy to drop voltage at 85%+ efficiency.
Thats not to say some reduction might be helpful, but I don't think your locos are necessarily going to burn themselves up.
mlehman BTW, that suggests that the OP may want to consider adjusting the power supply voltage to solve his problem, if it has a separate power supply.
BTW, that suggests that the OP may want to consider adjusting the power supply voltage to solve his problem, if it has a separate power supply.
I agree. Typically most circuits will transform any reduction in voltage (through a voltage regulator) into heat. In other words, the bigger the difference between input and output voltage, the more heat you will generate. If that voltage correction is done in the cab, that cab will get hotter reducing their lifetime. I would try to find a power supply closer to what you need. Or build a custom adjustable one like I did using a 18Volt laptop power supply
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
As per NMRA S9.1.70 n-scale should be around 12 Volts, with a minimum of 7VDCC and maxumum of 24VDCC
http://www.nmra.org/standards/DCC/standards_rps/S-91-2004-07.pdf
Some decoders can now start around 3Volts. This was to accomodate DC operations so the train could start as a lower voltage. This is obviously outside the NMRA spec. But the spec says, they only have to operate at 7VDCC, not that they can't go lower.
mfm37NCE boosters also have an adjustment inside the case.It's in the manuals.Its output is also regulated. I don't believe Powercab has an adjustment.
Since I happen to have the NCE manuals easily available, here's the exact lowdown on NCE voltage adjustment.
On the Power Pros, yes, cover has to come off and manual adjustment via screwdriver done. Operating voltage output can range from 9.5 to 18 volts, factory setting is 14 volts.
The PowerCab does have a provision for adjustment -- its voltage output is 0.5 volts less than the input. You can power it with anything from 10 to 15 volts (limited to 3 amps), giving an effective 9.5 to 14.5 volt output.
Mike Lehman
Urbana, IL
Standard N Scale voltage is 12 volts. Digitrax boosters (DCS and DB, not Zephyr) will put out 12 volts on the N Scale setting. It's a regulated output so it will be very close to 12 volts. Inside the booster is a pot to fine tune the output. Zephyr's do not have an adjustable output. The couple of DCS50's I've check were 13.8 volts.
NCE boosters also have an adjustment inside the case.It's in the manuals.Its output is also regulated. I don't believe Powercab has an adjustment.
MRC is not adjustable. They have recommended using diode pairs to lower output.
Not sure about other brands because I haven't actually checked them.
N Scale decoders should be able to withstand up to 22 volts on teh track if they are NMRA compliant. Soundtraxx used to be limited to lower voltage.
My BLI E's run fine on Digitrax N scale setting. Earlier this evening I test ran an Athearn with factory installed Tsunami sound decoder on our NTRAK layout to test things out for this weekend's Timonium show. It ran fine as did the layout.
Martin Myers
LakeDarrel, are you sure that it is the decoder that is making the shells hot or the LED's. I have two Atlas MP15dc with Digitrax decoders that have the the very small LED's that is embedded in to the board. These get so hot and that they almost touch the shell where it is lower in front of the cab, they melted holes in the shell above them.
That can happen. Especially since every electrical engineer who seems to work getting intensity levels prototypically reasonable has been laid off. They are all set to STUN it seems, except for notable exceptioons. Good a reason as any to dial back the voltage a little.
Really, it's all about adding some resistance.Tones down the light, cools things off with the more realistic resistance in the circuit. In reality, it depends how close the circuit was analyzed or someone didn't check those last voltage numbers before hitting Save or wrong part in the circuit... If it's bright, you can't hurt by adding ohmage. I've done circuits on my 12.5 volt power where 4k was pretty darn right for what I wanted. Use the right LED and it starts looking bulbish.
#100's blazing away in the roundhouse, will probably get that one dialed down a tad more.
Darrel, are you sure that it is the decoder that is making the shells hot or the LED's. I have two Atlas MP15dc with Digitrax decoders that have the the very small LED's that is embedded in to the board. These get so hot and that they almost touch the shell where it is lower in front of the cab, they melted holes in the shell above them. So now those engines with these do not have lights on unless actually moving. The decoders may be warm, but unless some thing is really wrong with your system or the decoders it is normal. I
Ken G Price My N-Scale Layout
Digitrax Super Empire Builder Radio System. South Valley Texas Railroad. SVTRR
N-Scale out west. 1996-1998 or so! UP, SP, Missouri Pacific, C&NW.
At our club, the HO and N scale layouts both use an NCE PowerHouse DCC system with a measured track voltage of 14.6 volts AC, with no noticeable harm to any of the N scale decoders.
Between N and HO scale decoders, the only difference other than physical size is the motor's current draw rating. HO scale decoders are usually rated for 1 Amp continuous and N scale 3/4 Amp, but they're all rated for the same input voltage range.
As far as I know, only Digitrax has different track voltage settings for the different scales. OK, O gauge should probably have a higher voltage, and if you are running O gauge, you usually have to buy a DCC system specified for O gauge. But the norm is the same voltage for HO and N. All the decoder manufacturers (except for Digitrax) don't specify a different voltage. 13 volts sounds right. My track voltage is 13.5 for my NCE HO scale layout. On our club N scale Digitrax layout, I am using the HO settings because it runs better.
Now let me add a couple of things, and these are personal opinions based on experiences I have had. I do not like MRC decoders, and I do not like Digitrax decoders. To me, these are not as easy to set up and program as other decoders. Digitrax has a quirk where BEMF is automatically turned off when the decoder is in a consist. No one else does that, and it doesn't appear to be advertised, but sort of hidden. My favorite decoders for N scale are TCS. For HO, I use Tsunami's or TCS. These manufacturers specialize in decoders only.
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.
Never heard of using rectifiers to adjust voltage myself, but I'm far from a DCC guru. However, is there no other way to adjust your output voltage? You might check the manual, unless you're certain that's not the case. With my NCE, it's a matter of adjusting a setting on the command station, so much more convenient and adjustable than anything that's hardwired.
It's a good idea for you to check on this if you have a hot engine. Might be worth checking the decoder documentation so you get an idea what the manufacturers are recommending as a voltage operating range for your engines. Somewhere there needs to be a sweet spot where everything plays well together and that might hel;p answer your original question, too.
I've been through some of this myself. If you have installed LEDs with resistors to look right at a higher voltage, once you dial it down may not look right. But it was worth getting things right. When Blackstone came out with their HOn3 C-19s a couple of years back, I decided to dial my NCE from 14.5 down to 12.5 volts to help the Tsunami-750s stay cool. It's worked well and the few adjustments needed were not a buig deal. Thing is you do wanna establish a baseline and try to hit that so it doesn't drive yu nuts everytime you buy a new loco.
I have a Digitrax Super Empire Builder and the track voltage is usually between 9-11 volts in the N gauge power setting, 12-14 volts in the HO power setting. My clubs two digitrax systems are about the same voltages the last time I had to check them.
I have read that most DCC systems produce too much track voltage for Nscale engines and the decoders ( sound decoders especially) may produce too much heat over time and shorten the life of the decoder or even melt plastic on the loco body. My BL Paragon 2 engine would not run without first lowering the voltage with rectifiers so I installed 4 rectifiers on my main buss. After doing that my Atheran F45 would not run I think because of too low voltage. I finally took 2 of the rectifiers back out and both engines now run ok but the BL seems to run hot (plastic is pretty warm). I tested the voltage and it appears to be about 13 volts. Does that seem like the proper voltage for DCC nscale layout with both sound and nonsound engines? Is there a standard nscale voltage or is each layout different depending on size and type, number of engines and etc?