Digitrax guidance with their devices is to avoid sharing power sources between dissimilar devices. The always suggest using (or sharing) the PS14 (or similar source) for similar device. In my case, I will have 3 sets of devices (DS64, PM42 and UP5/92) that need 12VDC power. If I use a PS14 for each individual device, that adds up in a hurry - even if I let some devices share a PS14 (within is power limits). I have a 12DV power supply that is more than capable of meeting the power requirement of all these devices. I would like to run a 12VDC buss around my layout and let each device tap into it. However, this would violate Digitrax guidance to avoid sharing a power supply between different devices.
Has anyone shared a power supply between different devises and suffered a problem? Is there a way/device to allow me to run multiple 12VDC lines from a single supply and to isolate each line so that each line operates idependently with no possibility for cross feed?
Paul D
N scale Washita and Santa Fe RailroadSouthern Oklahoma circa late 70's
If all of the devices use 12VDC power, and your single 12VDC power supply can handle the total amperage of the sum of the devices - I can see no issue here.
Now, on the other hand - With that single power supply, you have created a 'Single Point of Failure' that will disable all of those devices if it fails(the power supply). A PS14 provides 300ma of power, and costs about $10(discounted price). I have a UR91, UR92, and 5 UP5 panels - each has a PS14 wall wart. You can go on-line and find 12VDC wall warts for around $5 each...
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
This comes up every so often on the Digitrax Yahoo group, and the advise is to stick with the Digitrax recommendation of not powering different families of boards with the same power supply.
To the best of my recollection, the reason is that the various boards, designed at different times, have different internal power rectification circuits and certain combinations/fault conditions could destroy those boards.
I have a 12VDC, 2.1 amp buss (split and fused) for my DS64's, a 12VDC 1 amp buss for my UP5's, and the PM42, located by the DCS100, has it's own (12 or 15VDC, I don't recall) 500ma wall wart. Easier and cheaper than tracking down ground loops and replacing fried boards.
Hi, PED
I've been using Digitrax DCC for about twelve years now. My layout is fairly large occupying most of a 35 by 50 foot basement.
When I installed my UP 5s; UR 91 & 92s I used a common 1A 12V power supply and wired them daisy-chained. I kept them powered 24-7 since Digitrax suggested the battery "keep-alive" feature. I had the track indicator LED's wired to the track buss and the single jumper wire connected also as Digitrax suggested.
About two years ago I "upgraded" everything to Duplex walkaround. There were times that I whshed that I didn't do that BUT I have since worked out some of the early problems (headaches!) with my initial Duplex installation.
A few things I have learned. The UR 92s will not work with anything less than 14 volts DC. I had not discovered this until recently when I was doing further troubleshooting. That extra 2 volts makes a difference!
I had to upgrade the firmware on the throttles. I was not aware of any needed upgrades even though Digitrax converted two of my DT400 throttles to DT402Ds only a short time before the upgrades were made available. They had my contact information, an email would have been nice. Paul Cutler {Paul3} mentioned the upgrade here in one of his replies.
I had to upgrade the firmware on the UR92s as well.
After considerable troubleshooting, buying an additional UR92 and relocating them toward the ceiling the Duplex system seems to be working much better. I have since disconnected all the track indicator LEDs since reading about potential conflicts with the onboard circuitry. I eliminated all the daisy-chained UP5 common + connections, too.
So, to get back to your original question, yes, you can power your devices from a common supply. Just watch your polarity when you wire the 2mm power plugs and the total current draw (I seem to recall the UR92 draws about 300mA). I bought a bunch of plugs from All Electronics for that use.
I use a PM42 and it is powered by its own PS14 since it is near an AC outlet.
Good Luck, Ed
Ed,
It seems to me that you ARE following Digitrax's advice - All your UP's and UR's (one family) are powered by one supply, while your PM42 (another family) is powered by a separate supply.
You remember correctly - the reason for keeping things "all in the family" is that some devices have no input protection, some just a single diode, and some a full wave rectifier. Because of this, it's easy to get a dead short across one or more diodes on the device you are attempting to power once the Loconet cable is attached and there is now a common reference across all the boards. Sometimes you get all 3 inputs on the same board - in the Digitrax Yahoo Group files there is a power input schematic someone traced out from the DS64. Depending on the source being the track powerterminals, the ax1 and ax2 DC power connectors, or the barrel connector, you have different input circuits, some with diodes and some without.
Since it's easy to make a mistake that in the case of an individual board would not actually damage the board, but then because of the common connection through the Loconet signal cable end up creating a condition which can damage the board, best to just stick with the Digitrax recommendations.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
It is best to use 14VDC for powering devices. Many older items were designed to work with 12V and still do work some Digitrax devices are designed to work with 14VDC minimum. This is especially true of the UR92. The latest UR92 firmware requires 14 volts and will not work with less. PR3 performs better with 14 volts as well.
Sharing power between similar devices works well. Reasons for doing so have already been explained.
Martin Myers