Hello All
Do the Rail A and B inputs on the back of the UP5 provide power to the throttles or do they only indicate track power?
Thanks
Springfield PA
http://www.digitrax.com/ftp/up5.pdf
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.
Yes if the track power voltage is higher than the Railsync in the Loconet cable and higher than any power supply you might have plugged in to the coax port on the side. Each possible voltage path i protected by a diode so one won't feed back to any other, so highest voltage wins.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The reason I doubted that the rail input provided power is the manual doesn't mention it. It only shows that it activates the track status light.
It's at the end of the manual that Elmer attached. For powering throttles it notes to use the PS14 and doesn't mention track power.
There are three ways to provide power to throttles that are plugged into a UP5. A battery in the throttle is a fourth way.
First: The track screws on the rear will provide power to the front and side jack for throttles. These screws are also connected to a bicolor led on the front to indicate track power. This source can be troublesome because if track power is off (short circuit) there is no power for the throttle.
Second: Rail sync pins 1 and 6 of the loconet cable will provide power to a throttle plugged into the front and side jacks. This is the most troublesome source as too much draw on rail sync will pull loconet down. One DT400 or 402 throttle will usually be OK. Add more and loconet can become unstable with strange results.
Third: The coaxial auxiliary jack. Plug a 12 - 15 volt DC supply into this. The center pin is positive. It is connected to the front and side jacks as well as that little solder hole on the board between the rear jacks. This is why you can daisy chain one power supply through other UP5's using that small solder hole. Return path is through pins two and five of the loconet cable which is also connected to the outside barrel of the coax jack. At 12 - 15 volts, the coax jack will most always be the more dominant voltage to supply throttles.
UP5's have steering diodes on the board that keep all of the above from feeding into another. Their only electrical path is through pins 1 and 6 of the front and side jacks to throttles or other devices connected to those jacks. When a throttle is plugged in, the power source with the highest voltage will supply the throttle. If that only source is rail sync, it will draw power from there. If the throttle has a battery, it may still draw from one of the other sources until the voltage falls below that of the battery. Loconet will be stable at just below the battery voltage so the battery will "take over" as rail sync begins to fall close to the unstable level. All this in a UP5 for about $15.
A schematic of UP5's and UP3's can be found in the files section of the Digitrax Yahoo group. You should be able to access this file because you have been asking the same questions on that group.
Martin Myers
As I mentioned int he thread in the Yahoo group, lookign at the schematic you can see how the power flows. All common is throught he ground wire int eh Loconet cable - the - side of the coax connector connects there. The + side of the coax connector, both track screw terminals, and the Railsync lines in the rear jacks are all connected via diodes tot he Railsync pin on the front jacks.
Someone else asked about applying a 15VAC power supply to the screw terminals - no, that won't work as there's no return path, both screw terminals connect to the SAME Railsync pin, via diodes.
Here's the link to the schematic:
http://f1.grp.yahoofs.com/v1/8ObaTVonFYMDzdK2IBG5zzUswf9Cqw7IxUeYjwK26IrKd6AZisoHjMXMx9uZYiEvciPo9z6cdNZH8ORjKYfyxQQvx1s/UP3-UP5%20%26%20BDL16/UP5%20Circuit.jpg
Looking at it you can see that it would be a bad idea to use track power as a source for this module.
The Rail A and B inputs both go to a diode before feeding the side and rear connectors(full wave rectifier)
However there is no return path to the track. This results in the common wires in the loconet cable being the return wire. Add several boosters with all feeding rails going to UP5's and you have a major recipe for problems. Because of this I believe the manual was correct and that they didn't intend for it to be used as power, but I don't know why they would have put the diodes in with no return path. They should have used a bridge to do the job.
The bridge rectifier is in the throttle. The circuit is actually quite robust. Multiple boosters do not change this. Only one booster at most would be connected to a single UP5. Multiple boosters should have a larger gauge common wire connected between them.
Of course, if you have block detection the whole thing goes out the window, the draw from the LED and any throttle plugged in would trigger the detector so no hooking to track power downstream of a block detector.