This is Bradford Valley Lumber Company #9, a locomotive that's giving me a rather unusual problem at the moment. When I run it on my home layout, it will only run very slowly, much slower than it should be. However, when I run it on my programming/test track (Sprog 2, separate from layout wiring) or on my club's layout (Digitrax DCC), it will run as expected - speed, everything. The same thing happens with #5 (Bachmann Climax) and #8 (Bachmann HO 2-6-2 Prairie mechanism). I can't speak for the Climax, but I know #8 and #9 had to have TSU-2200 decoders, as the motor stall current was about 1.5A.
On top of this, I have several frog juicers on my layout, to provide power to point rails where I couldn't fit a microswitch. The first two worked alright, and so I installed a few more. Now some of them don't seem to work, and I get a short circuit when I should get a reversal of polarity. This seems to happen mostly with the ones in staging and at Camp D, which are the furthest away from the DCC system in terms of wiring.
The DCC system itself is home-built, with a Tam Valley Depot booster taking a DCC signal from an Arduino, which is then put out to the tracks. This is powered by a laptop power supply, which puts out 19v DC at 6.3A max. A voltage regulator steps this down to 12v, which is then used to power the Arduino and track. The regulator should be able to provide 4A, which is the maximum output of the booster.
I'm a bit stuck as to what's going on, and would appreciate any advice. I suspect I may need to add a second booster?
The Location: Forests of the Pacific Northwest, OregonThe Year: 1948The Scale: On30The Blog: http://bvlcorr.tumblr.com
tbdannyThe DCC system itself is home-built, with a Tam Valley Depot booster taking a DCC signal from an Arduino, which is then put out to the tracks.
is the AC track voltage on the programming track and the main layout the same?
greg - Philadelphia & Reading / Reading
gregc tbdanny The DCC system itself is home-built, with a Tam Valley Depot booster taking a DCC signal from an Arduino, which is then put out to the tracks. is the AC track voltage on the programming track and the main layout the same?
tbdanny The DCC system itself is home-built, with a Tam Valley Depot booster taking a DCC signal from an Arduino, which is then put out to the tracks.
I'm not sure - I'm unable to measure it at the moment, but will do so at the earliest opportunity. Both are being fed from 12vDC sources. Furthermore, my other locomotives (e.g. #4, an On30 4-4-0) don't exhibit this behaviour - they run identically on the programming/test track and the layout.
According to the Tam Valley site, if you are using a 12V DC power supply to their booster, it's only putting 10.5-11 volts on the rail. This is less than even Digitrax's N scale setting. Tam Valley reccomeds their 16V power supply when using the booster foor track power, which puts the track power at about 15V, which is typical for HO DCC.
So running trains on your club layout probably is giving them nearly 5 volts more, siginificant speed difference.
Tam Valley recommends a 12V power supply when using the booster to run their stationary decoder devices, since they all regulate down to 5V for the circuitry and to drive the servos, so the less it has to drop, the cooler it runs. They recommend the 16.5V power supply is using their booster to power track.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Ya I think the minimum DCC track power would normally be 14V AC. BTW I suspect what you're thinking is short circuit is actually an overload due to the low power.
That's hit the nail on the head. I've just measured my track voltage using the AC setting on my multimeter, and it's reading 11v. The simplest way to fix this would be to connect a wire directly from the positive supply of the power jack at the rear of the DCC system to the positive input of the booster board. This would give it the full 19v from the power supply. However, I'm concerned that this may put too much voltage onto the tracks.
the Tam Valley booster manual says the max power input voltage is 40V
gregc the Tam Valley booster manual says the max power input voltage is 40V
I checked that manual, but I couldn't seem to find anything about the output voltage. I'm not sure if it's relative to the input, or constant. I'll email Tam Valley and ask them.
i'm surprised that the booster doesn't limit the voltage to what DCC is expected to be.
The first page of the manual says the output is 1V less than the input voltage, which elsewhere it says should be between 12-18V.
The Mark Gurries site says the DCC track voltage should be 14V. So you would need a 15V supply. But read what Randy said earlier
As an example. my NCE Power Cab has a 13.9 vdc wall wart and the DCC voltage on the track with a loco is 13.6 vac with a Harbor Freight multimeter. I have four of those meters. Those meters are pretty decent for the price. I have used them for about nearly ten years. Generaly the only ones who say they are not accurate are those who do not use them.
My digital scope shows about the same when I do the math. Even my TEK 475 scope agrees. That was a top of the line dual trace scope at one time. Scopes measure peak to peak voltage.
The club NCE five amp Power Pro is the same voltage.
Rich
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.
The Tam Valley boosters output relative to the input. Since they are DC input there is probbaly only a single diode for reverse protection ince case you hook the poower supply up backwards, plus any associated diode drops in the drivers. They aren't regulated, so if they can handle 40V input, they will put out 38-39 volts and fry pretty much any decoder. Even the NMRA standards only specify tolerance to 22 or 24 volts.
Thanks to all four the replies.
The voltage regulator board I used can also be set for 15v, so I'll use a second one of them to provide 15v to the booster. As long as it has a common ground with the Arduino, it should work.
I'll also set the original regulator, which will now only be powering the Arduino, to 9 volts. This means it won't have to deal with too much excess voltage.
The input to the booster should just be looking for a differential input, so it doesn't even necessarily need a common ground to the Arduino. The input just feeds the LED side of an optoisolator. Basically, it's like hooking an LED to the output of the Arduino command station. If using multiple Tam Valley boosters, a ground between them is pretty essential as a split pickup loco crossing the gaps between boosters cooould in some cases see double track voltage if not for a reference ground. But since the inputs are optoisolated, there's no way for any power to feed back through the lines connecting the multiple booster inputs - this also means they should be good for common rail wiring (not that anyone should be wiring DCC for common rail---right?).
It works!
Thank-you Greg, Randy, Stix and Rich. Based on your advice, I added a second regulator board into the base station. The Arduino is now running off 6v, and the DCC booster off 15v. This is giving me about 14.3v on the track. It's also banished all the little electrical gremlins. My locos are running properly, and all the Frog Juicers are working without issue. Thank-you again for the advice.