gregci don't know exactly how much current my locos draw.
Wire a multivolt meter in series with a DC power pack on a section of track. Aligator clamps and a harbor freight MVM set to measure current are all you need for this (I used the Radio Shack verison of the kit multi-volt meter).
That will get you in the ball park..
Early on in my DCC pursuits, I purchased a RRampMeter to measure voltage and amps. Some guys complain about the price. Others just use a multi meter. Still others build their own. To me, the RRampMeter was the best DCC related purchase that I ever made. You need it, or something like it, to protect your DCC system.
Rich
Alton Junction
rrinker In the data sheet of power drivers and things like voltage regulators, there are specificatioons for maximum current, assuming a heat sinking capacity that is alsooo specified. Using less or no heat sink, the devices won't instantly fry, but they will be unable to deliver that same maximum power without failing. Combined with an enclosed plastic case with little or no ventilation, you can build up quite a bit of heat, certainly enough to melt plastic. 2 amps at 15 volts is 30 watts
this looks like the power dissipated by the load (the output is 15V, right), not the power circuit on the heat sink?
the power dissipated by a linear voltage regulator depends on the difference between the unregulated input voltage and the output voltage. If the input is 20V, the output 15V and 2A, the regulator is dissipating 10W.
rrinker Assuming they are using power MOSFETs for the H bridge driver.
if they are using bipolar transistors, the power dissipated depends on the saturation voltage across the transistor which is 3.0V for an 2n3055. This means 30W for each of the two active transistors in the H-bridge or 60W lost in the power circuit using bipolar rather than MOSFETs which would only dissipate 8W.
with this in mind, why wouldn't you assuem they are using a MOSFET in a high power h-bridge?
BMMECNYCOr just budget your current draw to 2amps?
i don't know exactly how much current my locos draw. I use a 1+A lamp for protection and short indication. I have a cranky boxcab that sometimes causes the lamp to glow.
i understand that circuit breakers don't trip immediately. The diagram below illustrates that a home breaker will trip faster depending on how far above the trip current the actual current is.
I don't want my PowerCab to shutdown immediately if 2A is exceeded unless it's a short (some max current limit). Maybe it should after a 60 seconds if it's 2.1 A.
i had expected the PowerCab to protect itself both from damage to the electronics, as well as from melting. I don't want to spend an additional $20 for a circuit breaker to protect the PowerCab from damage. I don't want to monitor the current meter on the PowerCab (maybe there's a way to specify the shutdown current). I did install a lamp similar to the NCE CP6.
again, all this discussion helps me better understand this equipment, its limitations, how to use it better and how to build my own.
greg - Philadelphia & Reading / Reading
Circuit breakers have what is called an instantaneous trip and a delay trip. Yes you can exceed the rated capacity for short periods. The idea being that you dont want small short (time) duration spurious conditions to trip things off. You do want it to trip instantaneously when a high inrush condition occurs (as in a short circuit). Typically "things" are designed to somewhere around 150% of their nameplate rating. This provides you with a margin to safety. Operate at the nameplate rating of the device, not the technological limit.
gregcthere would be 0.36 W in a PowerCab supplying 3A, if similar mosfets are used. I don't see any openings in the PowerCab for ventilation. (maybe I should cut some).
Im pretty sure that if you modify your power cab, operate it over the limit, NCE isnt going to warantee repair the thing.
Ive used mine for hours, as have many others, without exceeding the 2 Amp rated capacity.
Or just budget your current draw to 2amps?
Why all the fuss over three amps. The manufacturer states its a 2amp system. Dont exceed 2 amps and you will find that it will last you a long time.
To answer your question on the circuit breaker, typically they trip at the setpoint you choose. 2.5A = 2.5A. You can have a short that persists if you dont wire your layout properly.
Assuming they are using power MOSFETs for the H bridge driver. Have to dig in and see just what they are using. There is an integrated audio amp IC that is often seen in low power (~3 amp) DIY booster designs that likely does not have such a favorable RDSon. Somewhere I have a couple, I once was going to build one for an accessory power booster. It requires very little in additional circuitry to take a low power DCC dignal and produce a proper track level output.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinkerIn the data sheet of power drivers and things like voltage regulators, there are specificatioons for maximum current, assuming a heat sinking capacity that is alsooo specified. Using less or no heat sink, the devices won't instantly fry, but they will be unable to deliver that same maximum power without failing. Combined with an enclosed plastic case with little or no ventilation, you can build up quite a bit of heat, certainly enough to melt plastic. 2 amps at 15 volts is 30 watts - ever try to touch a 25 watt light bulb? Pushing it to 3 amps is 45 watts. Seems reasonable to me that running the thing continuously at 3 amps is going to cause issues.
Combined with an enclosed plastic case with little or no ventilation, you can build up quite a bit of heat, certainly enough to melt plastic.
2 amps at 15 volts is 30 watts - ever try to touch a 25 watt light bulb? Pushing it to 3 amps is 45 watts. Seems reasonable to me that running the thing continuously at 3 amps is going to cause issues.
since DCC is PWM, the power dissipated by the circuit is based on the on resistance of a mosfet and the max current being supplied.
The on-resistance for some high power mosfets i have is 0.04 Ohms. At 10A, each dissipates 4 watts (R * I^2). Since there are two mosfets active at a time in the H-bridge, that's 8W. Isn't 8W comparable to todays LED lamps?
there would be 0.36 W in a PowerCab supplying 3A, if similar mosfets are used. I don't see any openings in the PowerCab for ventilation. (maybe I should cut some).
(unable to quote)
rich
the doc say short protection. we know it works.
So yes, I was asking what happens if you exceed the 5A rating of a PowerPro by 1A.
if there were a circuit breaker set to 5A, wouldn't you expect it trip?
There's a big difference between the PH-Pro and the powerCab with regards to the track power circuitry - in the PH-Pro you have a much bigger METAL case that helps dissipate heat. Pretty sure on pictures I've seen of the insides there's a large heat sink attached to the drivers that control the track power. That SHOULD give them components plenty of head room over the nominal output power for the protection circuitry to trip without frying anything first. But in the PowerCab - they had room left over after the normal cab functionality (remember is it and can be used as a normal ProCab when plugged in to a PH-Pro system) that they were able to add the circuitry to generate a DCC sisgnal to the rails. But that was squeezed into a PLASTIC case that already has lots of other components in it. Not much room for a heat sink, either, if there even is one attached to the main power driver. This can be perfectly fine, depnding on the intended use. In the data sheet of power drivers and things like voltage regulators, there are specificatioons for maximum current, assuming a heat sinking capacity that is alsooo specified. Using less or no heat sink, the devices won't instantly fry, but they will be unable to deliver that same maximum power without failing. Combined with an enclosed plastic case with little or no ventilation, you can build up quite a bit of heat, certainly enough to melt plastic. 2 amps at 15 volts is 30 watts - ever try to touch a 25 watt light bulb? Pushing it to 3 amps is 45 watts. Seems reasooonable to me that running the thing continuously at 3 amps is going to cause issues. If not melting the case, then way overheating the internals of the power device. Not knowign what they use, I can;t look at a data sheet, but the data sheet would also have information on the temperature rise of the device internally, and maximum allowable temperature. This can be a temperature that is far higher than comfortable to touch, while the attached heat sink remains just warm.
I ran my Power Cab with some sound locos and shut down the cab a few times but never damaged the Cab. No idea hwo someone did.
I did the quarter test a few times and the Cab tripped. No problem.
The club did test with the Power pro a few times and no problem.
The only issue with the Power pro was when we had fourteen blocks switching from DC to DCC and still ran HO DC and DCC we had somone cross a block with couple DC locos and smoked the booster. The DC throttle could handle three amps.
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
gregc of course you're not going to have these problem with a PowerCab if you add a booster or a circuit breaker. richhotrain gregc The PowerPro documentation says that the PowerPro is rated at 5A and will shutdown if a short is present for more that 1/2 sec. It's unclear what it does if it operates at 6A for many minutes. 6A is not a short.
of course you're not going to have these problem with a PowerCab if you add a booster or a circuit breaker.
richhotrain gregc The PowerPro documentation says that the PowerPro is rated at 5A and will shutdown if a short is present for more that 1/2 sec. It's unclear what it does if it operates at 6A for many minutes.
gregc The PowerPro documentation says that the PowerPro is rated at 5A and will shutdown if a short is present for more that 1/2 sec. It's unclear what it does if it operates at 6A for many minutes.
The PowerPro documentation says that the PowerPro is rated at 5A and will shutdown if a short is present for more that 1/2 sec. It's unclear what it does if it operates at 6A for many minutes.
6A is not a short.
Greg, regarding your last sentence, like anything else, you get what you pay for. My guess is that the manufacturers (of anything for that matter) develop a product with an eye to a certain price point and a certain market. I am sure that the technology exists, or can be developed, to prevent a product from self destructing. But you are going to pay for that technology.
Bear "It's all about having fun."
i learn a lot from threads like this. thanks to all
heat is what typically damages electronic component (besides dropping them). Some transistor inside an integrated circuit gets too hot and melts.
Rich's post about the powercab shell deforming due to heat is the first I've heard of electronic equipment continueing to operate but the plastic melting.
and the temperature of the electronics depends both on the load and amount of heat it is generating and it's ability to disippate it. They will get hotter if the ambient room temperature is higher, the equipment is in a hot attic, on a sunlit shelf or a poorly ventilated area.
the manufacturer of that transistor may have it rated at some current that is determined such that 99.9...% of the parts won't fail at that current at the specified temperature.
that doesn't mean that they fail if the current is exceeded by 0.1A or even 1A, especially if the ambient temperature is cooler.
i realize that i was wrong in my original post. That at least the PowerCab and PowerPro, have short circuit protection for shorts that persist for 1/2 sec. This is not the same a protecting against exceeding the current rating of the unit.
The DB3 booster limit is vague
The DB3 requires a 14-18 Volt AC transformer (or 18-24 Volt DC power supply) capable of supplying 3 or more Amps.
at what point does it melt ;)
i'm surpised by the test for the EB1 circuit breaker
After setting the trip current we recommend testing your wiring. The “quarter test” is the fastest way to test your wiring. Use a coin or other piece of metal to short across the rails atvarious places in a power district.
if you set it for 2.5 amps, will is trip at 2.6?
not all components are the same. If you have a problem with a PowerPro supplying 5A, it sounds like NCE will repair or replace it. Most units can probably supply more than that. And they certainly shouldn't even start to melt if you just exceed the limit.
The PowerCan design is actually impressive. The electronics can exceed the "stated" capacity of 2A by 50%. The limiting factor is not the electronics, but the plastic. wow!
so, i now have a better understanding of the limitations of these products. I can now understand why some say you really need a circuit breaker.
i'm disappointed that NCE only has short circuit protection. I helped work on the protection firmware for our product. I see no excuse preventing products from self destructing with the technology in DCC products.
The throttle would melt. But, then, I am not about to conduct an experiment along these lines.
bearmanIf I were to opine on exceeding the 5 amps, I would opine that at some point you have a gob of plastic which at one time was a Power Pro throttle.
huh?
If I were to opine on exceeding the 5 amps, I would opine that at some point you have a gob of plastic which at one time was a Power Pro throttle.
Who is going to run any system at its rated capacity? I mean, I am not going to get on the German autobahn and drive my 200,000$ Ferrari at just below the red line, for two reasons. One, I don't own a Ferrari, and two I would be scared to go that fast.
Rich is correct, I believe. The Power Cab has been marketed as a starter set per his description. And, it makes no sense to spend all that money on a PH-Pro when you dont need all that amperage punch because of the size of your layout, the difference in MSRP being over 300$
And, circuit breakers make sense reagrdless of the DCC system that is being used.
gregc thanks Rich. i like my PowerCab and other NCE products. But with the technology in such a product, I had expected it to protect itself ... completely. Now I have doubts. The PowerPro documentation says that the PowerPro is rated at 5A and will shutdown if a short is present for more that 1/2 sec. It's unclear what it does if it operates at 6A for many minutes. these products measure current and track time. couldn't they shutdown automatically if they are operated above their rated current for more than an accumulated period of time for some limited time (don't restart the timer if it momentarily drops below max current). from the PowerCab doc: "You cannot run 3 Amps continuously for the PowerCab". How long can you operate it at 3A? When should you get worried? If heat is the problem, it would have been better if they added a temperature sensor. Please don't interpret this criticism as slight against NCE products. I like my PowerCab and would buy other NCE products. But now I'm glad I added the bulb that limits current to 1.5A
thanks Rich.
i like my PowerCab and other NCE products. But with the technology in such a product, I had expected it to protect itself ... completely. Now I have doubts.
these products measure current and track time. couldn't they shutdown automatically if they are operated above their rated current for more than an accumulated period of time for some limited time (don't restart the timer if it momentarily drops below max current).
from the PowerCab doc: "You cannot run 3 Amps continuously for the PowerCab". How long can you operate it at 3A? When should you get worried? If heat is the problem, it would have been better if they added a temperature sensor.
Please don't interpret this criticism as slight against NCE products. I like my PowerCab and would buy other NCE products. But now I'm glad I added the bulb that limits current to 1.5A
The preferred method for adding more capacity to the Powercab is with the SB5 Smartbooster.
As I understand the Power Cab, it isn't really designed or intended as a mini version of the PH-Pro. Whereas the PH-Pro comes with its own 5 amp booster, the Power Pro is designed differently. It seems to me that NCE introduced the Power Cab as a "starter" system for guys with very small layouts and very few locos.
That's why whenever I get the chance to reply to anyone who is debating between the Power Cab and the PH-Pro, I urge them to purchase the PH-Pro. To effectively use the Power Cab on mid to large layouts, you should upgrade to a 5 amp booster, and if you follow NCE's advice, you wind up installing circuit breakers as well to protect the Power Cab.
https://ncedcc.zendesk.com/hc/en-us/articles/201479815-Step-1-The-Power-Cab
The 1.65 manual on this page only mentions a 3amp powersupply being the max power supply that you can use. I did not find those words in the manual.
gregcWhen should you get worried?
Over 2amps, which is the stated capacity of the system.
gregcIf heat is the problem, it would have been better if they added a temperature sensor.
If you were running 4 locomotives (HO) or 8 (N) per the manual above, you would never have heat problems.
Heat is generated by resistance. Learn about Ohms law and Joule's first Law here:
https://en.wikipedia.org/wiki/Joule_heating
https://en.wikipedia.org/wiki/Ohm%27s_law
Overheating is only a problem when you exceed the rated capacity of the system.
Ultimately this whole discussion is academic. In my opinion, if you are going to run 10, 20 or 30 locomotives you are going to make sure that your system can handle the current draw with some room to spare. It doesn't matter what brand you have.
Please don't interpret this criticism as slight against NCE products. I like my PowerCab and would buy other NCE products. But now I'm glad I added the bulb that limits current to 1.5A.
Well... that was a mess! I didn’t want to change all the locos to 3 so I changed the recalls on the cab to 6. also the locos (except for 3 in a consist are not speed matched.
I was doing pretty good until I got to loco #7 (consist plus 4) then some started to get too close to others and I was recalling-recalling-recalling trying to adjust everything .
Finally I gave up. But it was fun. Probably wont do that again.
Gary
gregc cowman Not sure about the PH Pro system, but I have a Power Cab and did damage it by running too many sound locos for too long a duration. wow! if something is rated at a specified current, i would expect it to work at that current non stop, not for some unspecified amount of time. Makes me wonder about other NCE products. I have a PowerCab.
cowman Not sure about the PH Pro system, but I have a Power Cab and did damage it by running too many sound locos for too long a duration.
wow!
if something is rated at a specified current, i would expect it to work at that current non stop, not for some unspecified amount of time. Makes me wonder about other NCE products. I have a PowerCab.
Here is what NCE has to say about current draw as it relates to the Power Cab:
OTHER CONSIDERATIONS:
A) You cannot run 3 Amps continuously for the PowerCab. It will overheat with the PowerCab shell deforming due to the high heat build up. It is strongly recommended you use multiple DCC circuit breaker with each set 2 amp trip current for the layout. The PowerCab feeds all of these circuit breaker which then feed the various parts of the layout. The DCC circuit breakers will isolate any short circuit and protect the PowerCab from over heating when there is a short circuit.
B) The PowerCab long flat cable will lose a lot of voltage and may get warm when running a lot of trains. The cable and associated telco RJ jacks and plugs are not really designed to support 3 Amp efficiently.
cowmanNot sure about the PH Pro system, but I have a Power Cab and did damage it by running too many sound locos for too long a duration.
our femtocell shuts down when temperature limits are exceeded.
Not sure about the PH Pro system, but I have a Power Cab and did damage it by running too many sound locos for too long a duration.
The folks at NCE were able to repair it at a reasonable price and advised me to either not run so many locos at a time or get a booster. At this time I am running fewer locos, but when I build my new layout, I will add a 5A smart booster.
Good luck,
Richard
For less than twenty dollars you can build this DCC amp meter using a Harbor Freight multimeter on the 20ma DC scale. The ZXCT 1009 does the conversion.
http://www.circuitous.ca/DCCammeter10.html
I built two about ten years ago. One for me, another for the club NCE five amp Power Pro system.
I had four of the meters at about two dollars a piece at the time and the kits cost me a few dollars each.
I remember we ran I think at least ten locos and I think about three amps at least half maybe more were sound.
I tested the system with a rheostat and it shut down at about 4.97 amps.