2 40' sections with the booster in the middle is always going to be better than a single 80' long section with the booster at one end. 40 feet of wire will have half the losses of 80 feet of wire.
If you use an absolute maximum bus length of 50' - with 2 booster, you could run 200 linear feet of layout with no bus line more than 50'. Maximum coverage with minimum bus length. Always bet practice.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
RR_Mel Did you try a couple of different locomotives to compare to your RS1?
Did you try a couple of different locomotives to compare to your RS1?
That will make testing so much easier and more accurate than manually connecting the 1156 bulb to the rails for each measurement and using an AC voltmeter. I hope to get the RRampMeter in a few days to continue the testing with a variety of locomotives.
Rich
Alton Junction
Did you try a couple of different locomotives to compare to your RS1? Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
T
RR_Mel I wouldn’t worry about a ¼ volt drop. I run dual mode DC or DCC and everything works great.
I wouldn’t worry about a ¼ volt drop. I run dual mode DC or DCC and everything works great.
RichI really don’t know, from my experience a ¼ volt isn’t enough to worry about. My layout mainline is only 120’ total (HO scale twice-around) and when I first tried rewiring my layout from DC to DCC (2006) I followed the DCC gurus way of buss wiring and I wasn’t happy with the results.My DC layout was wired for DC block control and the DCC buss wiring really screwed everything up. After several months of trying to adapt to DCC buss wiring I ripped everything out and rewired it back to my original DC block wiring. I use #20 AWG bell wire homeruns from each block to my control panel, longest run is about 15’ and at 1½ amps (two locomotives full load on my 3½% grades) the voltage drop is .15 volts.I ended up hooking my DCC controller to my DC block wiring and I’ve never had any problems, my blocks average 8'.I wouldn’t worry about a ¼ volt drop. I run dual mode DC or DCC and everything works great.
The only difference is your NCE voltage is lower than my Prodigy. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
gregc can't see that it will make a difference if the ends of the bus where the booster connects are just a few feet apart on the track. i think it would make a big difference is the booster connects to opposite ends of the track.
can't see that it will make a difference if the ends of the bus where the booster connects are just a few feet apart on the track.
i think it would make a big difference is the booster connects to opposite ends of the track.
RR_Mel That would be better, that would decrease you loss to about .45 volts max. And remember your test was at 2 amps so normal running only about .25 volts loss improvement.
That would be better, that would decrease you loss to about .45 volts max. And remember your test was at 2 amps so normal running only about .25 volts loss improvement.
richhotrainEssentially, the booster sits at the top of the U-shape bus.
i think it would make a big difference is the booster connects to opposite ends of the track
greg - Philadelphia & Reading / Reading
That would be better, that would decrease you loss to about .45 volts max. And remember your test was at 2 amps so normal running only about .25 volts loss improvement. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
One area of my layout is powered by a pair of bus wires running in a U-shape under the mainline tracks with a total length of 80'. Essentially, the booster sits at the top of the U-shape bus. Would it make any difference if I powered both ends of the U-shaped bus versus breaking the U-shaped bus in half so that one 80' bus becomes two 40' busses?
The following diagram illustrates this arrangement with the black line representing the 80' length of mainline track, and the red lines representing the bus wires feeding from the booster. The black circle at the bottom of the diagram represents the proposed break in the bus wires to convert an 80' run into two 40' runs.
RR_Mel I checked the web for the DB5 and the manual says there is a switch on the P514 Power Supply for 12 or 13.8 volts. Is it in the 13.8 volt position?
I checked the web for the DB5 and the manual says there is a switch on the P514 Power Supply for 12 or 13.8 volts. Is it in the 13.8 volt position?
richhotrain RR_Mel I would watch your RRampmeter, if the voltage goes up (current goes down) with loss of speed that’s an indication of more resistance between the locomotive and track power. If the current goes up (voltage goes down) as the locomotive slows that is more load applied by the locomotive. Wow, that is extremely helpful. Thanks again, Mel. Rich
RR_Mel I would watch your RRampmeter, if the voltage goes up (current goes down) with loss of speed that’s an indication of more resistance between the locomotive and track power. If the current goes up (voltage goes down) as the locomotive slows that is more load applied by the locomotive.
I would watch your RRampmeter, if the voltage goes up (current goes down) with loss of speed that’s an indication of more resistance between the locomotive and track power. If the current goes up (voltage goes down) as the locomotive slows that is more load applied by the locomotive.
Wow, that is extremely helpful. Thanks again, Mel.
That is a great tip... I am going to need to keep that one in mind for future use.
-Kevin
Living the dream.
When we were testing voltage drop on NTRAK modules to develop a revised wiring and connector spec we used a pair of 8 ohm/ 10 watt resistors connected in parallel. This works out to 4 ohms resitance. 3 amp load with our 12 volt boosters, measurements were taken first at the booster terminals using the resistor combo and a RRampmeter. Additional measurements were taken at each module joint which works out to about 6 feet of bus wire and 4 feet of track. I also repeated those measurements with my own DVM and readings were the same. At 80 feet voltage was down to about 9 volts using 12 ga cable and Anderson Powerpoles at each connection. We settled on a reasonable maximum one way bus length of 35 - 40 feet to avoid too much voltage drop. Fixed layouts will probably fare better as the construction and wiring will be in a controlled environment and not subject to a broad range of construction abilities.
I have a Rob Paisley DCC ammeter in my control panel using a LCD digital meter for current and a LCD DC volt meter both tweaked to be accurate on either DC or DCC mode. I run dual mode on my layout and always keep my eye on the meters when operating. The current increases as my locomotives clime my 3½% grades and decrease when going down hill. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
I would watch your RRampmeter, if the voltage goes up (current goes down) with loss of speed that’s an indication of more resistance between the locomotive and track power. If the current goes up (voltage goes down) as the locomotive slows that is more load applied by the locomotive. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
RR_Mel Your layout wiring is well within DCC operating specs.
Your layout wiring is well within DCC operating specs.
This coming week, I am going to test a number of my locos, diesel and steam, to see if the slow down is real or perceived. I will note specific points on the layout, if any, where a number of locos may appear to be slowing down and then speeding up again. My recollection from prior testing on my new layout is that there were a few such spots.
RichRemember your testing was done at two amps and the normal load from a running train should be well under one amp so the actual voltage loss at 80’ would be around .25 volts.With your locomotive (train) running the voltage at 80’ would be close to what your RRampmeter measures minus .25 or .30 volts. An older Athearn BB with the original motor would draw close to 1 amp so the voltage loss would be a bit higher, around .45 volts.Your layout wiring is well within DCC operating specs. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
I just went downstairs to the layout to measure voltages without load directly at the two boosters.
Using a digital voltmeter, I get the following readings:
PH-Pro - 14.31v
DB5 - 14.03v
The boosters are wired (14 gauge solid copper) directly into RRampMeters Here are those readings which are probably more accurate for DCC than the digital voltmeter.
PH-Pro - 13.9v
DB5 - 13.6v
gregc richhotrain How much voltage drop can occur across the mainline track before locomotive slowdowns visibly (and electrically) begin to occur? none, if a decoder uses BEMF to measure speed and the track voltage is sufficient to provide the necessary voltage to the motor. if there is no BEMF, the decoder provides voltage for a percent of time proportional to the requested speed and the loco voltage/speed will be proportional to the track voltage even when going slower, ... but the track voltage will also be inversely proportional to the current being draw. so there will be a bigger effect when drawing more current. i thought you said earlier that you noticed the loco slowing down, so the decoder in that loco probably doesn't have BEMF
richhotrain How much voltage drop can occur across the mainline track before locomotive slowdowns visibly (and electrically) begin to occur?
none, if a decoder uses BEMF to measure speed and the track voltage is sufficient to provide the necessary voltage to the motor.
if there is no BEMF, the decoder provides voltage for a percent of time proportional to the requested speed and the loco voltage/speed will be proportional to the track voltage even when going slower, ... but the track voltage will also be inversely proportional to the current being draw. so there will be a bigger effect when drawing more current.
i thought you said earlier that you noticed the loco slowing down, so the decoder in that loco probably doesn't have BEMF
The reason that I started this thread was because I was testing passenger car performance for possible derailments. To keep testing simple, I just started using an Atlas RS-1 loco with a DASR decoder to pull the passenger car consists. So, the loco slowdowns may be specific to just this particular loco.
But I started this thread to learn more about how to test voltage under load at specific points on the layout. So, the replies to this thread have helped greatly to understand the voltage measuring process.
What I need to do now is to run various locomotives and locomotive consists up and down the mainlines to see if there are noticeable slowdowns at specific points with a number of locomotives. My recollection from earlier testing is that there are a few specific points on the manlines where locos in general slow down a bit before resuming expected speeds.
richhotrainHow much voltage drop can occur across the mainline track before locomotive slowdowns visibly (and electrically) begin to occur?
none, if a decoder uses BEMF to measure speed and the track voltage is sufficient to provide the necessary voltage to the motor. this implies that if higher speed and voltage are required, there's a point where the decoder cannot provide enough voltage and the loco is slower than desired
RR_Mel The loss in your buss and track is only off ¼ volt from calculated losses. The starting voltage is too low as compared to my Prodigy.
The loss in your buss and track is only off ¼ volt from calculated losses. The starting voltage is too low as compared to my Prodigy.
But, let me ask this question. How much voltage drop can occur across the mainline track before locomotive slowdowns visibly (and electrically) begin to occur?
Take, for example, the readings that I reported yesterday. The voltage drops that occurred over an 80' stretch of track reduced the voltage from 12.21 volts to 11.45 volts. Is that 0.76 voltage drop enough to adversely affect locomotive performance?
I checked the web for the DB5 and the manual says there is a switch on the P514 Power Supply for 12 or 13.8 volts. Is it in the 13.8 volt position? Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
The loss in your buss and track is only off ¼ volt from calculated losses. The starting voltage is too low as compared to my Prodigy. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
RR_Mel Can you switch boosters or power it from the master to see if the voltage is higher.
Can you switch boosters or power it from the master to see if the voltage is higher.
The voltages are low but close enough between measurements to be usable. My Prodigy runs 14.6 volts with a 2 amp load.Can you switch boosters or power it from the master to see if the voltage is higher. I think your track and buss wiring is within limits and should be OK. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
I wound up taking 13 readings, about one every 6'.
Here are the readings from east to west over about 80'.
Some interval readings are greater or lesser than perhaps expected, but I think that is because some feeders are closer than 3' to each other but on separate sections of flextrack. The voltage drop seems to be, on average, about 0.06 volts for every 6' of track.
It should be about .015 to .02 volts per 3' difference. At 80' the voltage should be around 12.25 to 12.35 volts. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
RR_Mel Yes, acording to your post 12.78 is your reference voltage.
Yes, acording to your post 12.78 is your reference voltage.
Yes, acording to your post 12.78 is your reference voltage. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.