Last night I was connecting 12V DC power to my DS64 via the AUX +/- connections. The loconet cable was already plugged in. I found that when I connected only one of the two wires, the unit started working. This is not explained anywhere In the manual!
Also, it says the DS64 can drive two stall motor switch machines. Does that mean 2 tortoises in parallel? No max continuous current spec is provided. It seems to work ...
Anyone else seen this?
NP
1) I don't know this for a fact, but since LocoNet can supply/sink a certain amount of current, something like this might be possible depending on the circuit paths within the DS64.
2) Yes, two Tortii or similar stall motor machines in parallel. I have a couple or maybe three crossovers on my layout wired in that manner.
Where were you getting the 12V from? Probably just using the Loconet ground to complete the circuit. On the Yahoo Digitrax group in the files section there is a schematic of the input of a DS64 - be very careful which connections you use for power to them because you can easily fry an internal diode or two because of the way the different connections interact. IIRC, the safest thing, if you are using Loconet to control them (as opposed to DCC track packets), is to connect an AC source to the track inputs.
The same sort of thing happens when you add an additional booster - the common reference point is made via the thin Loconet cable, which in a short condition could carry the full booster power (and fail doing so) - this is why you connect a heavy wire between the ground terminals on the command station and booster (ideally, at least the same size wire as your DCC bus).
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thanks Stevert. The Tortii respond with much more enthusiasm to a DS64 compared to an SE8C ...
Randy,
I am running a separate 12V DC line around the layout from a 1A source. This is why I was surprised that it worked ... but I did have a BDL168 and an SE8C connected to the same 12V supply and that' probably created a ground path for the 12V.
Be very careful when powering multiple types of devices from a single supply.
Because of differences in their power rectification circuits, it's possible to damage them by doing so. This is also documented in the file section of the Digitrax group Randy referred to. Your DS64 experience might be related to that issue.
For Digitrax accessories, the recommendation is to power each type of device with it's own supply. In my case, I have one supply for my PM42, another for my DS64's, and a third for my UP5's.
Yes, that is exactly why it worked, the same supply being used for the BDL168 and SE8C. Internal ground path. As Steve said, you need to be careful with what devices you share power supply with, at issue is that some have just a half wave rectifier and others have a full wave bridge. The simplest way to avoid any issues is to only power like equipment in common, but there have been many discussions over the years on the Digitrax group about which devices can safely be powered off the same power supply. It becomes especially important with devices like the DS64 which have multiple power connections. In some cases all is well if you are consistent with the polarity, but mix one up and you get a dead short across a diode, or through the Loconet cable.
A follow up question-
Do you know if the SE8C handles two parallel tortoises?
the stall current of the tortoise is 16 ma, that feels pretty benign ... But again the Digitrax manual does not spec this.
Probably, but the SE8C is less than ideal for using Tortoises to operate turnouts, it runs them on rather low voltage to begin with. I doubt you can double up all 4 outputs, that will probably exceed the total current rating for the driver chip. Have to see what chip they use and check the spec sheet. I don;t have an SE8C to look at - if you follow the traces from the edge connector points where you connect the Tortoises they should all go into one chip on the board.
I will check today! Thanks!!