One transformer driving two boostersgreenspun.com : LUSENET : Wiring for DCC : One Thread
Is there any problem using one power supply to drive two DCC boosters? Does it make any difference if the power supply is AC or DC, and does it depend on the booster (reverse loop or not) or the manufacturer? The assumption is that the power supply has enough current capability to drive two boosters. I have seen manufacturer's literature not recommending it, no reason why, and then I saw a diagram in the EasyDCC manual showing one supply connected to two boosters. I'm confused...is this permitted or is it not? Any help would be appreciated. Regards, Knut
-- Knut Schartmann (email@example.com), April 19, 1999
Yes, there is a problem. See my April 15th answer to the 'common rail' issue in that message thread. For trouble free operation in this regard... Each booster should have its own isolated transformer winding; and/or They should not be powered from the same dc source.
Bridging the rail gaps momentarily connects the two booster outputs together. Sneak power paths are created if the DC busses or AC input sources are also connected together.
-- Don Vollrath (firstname.lastname@example.org), April 19, 1999.
I agree - you should use separate power (AC) supplies. Keith at EasyDCC allows for one big transformer - but really doesn't recommend it except for very simple layouts where you're only using multiple boosters for separation. Besides the grounding issues and sneak paths - theres the problem of voltage sag with ony one power supply - particuliarly when double heading and crossing a gap. You should use AC power supplies with the EasyDCC boosters as they have a nice bridge and filter capacitor arrangement on board. Be sure and use both of the RS1 and RS2 .27 ohm 5 watt resistors (some kits where shipped with only one - the assembled units come with two). I use a Hamilton 166P18 18 volt 5 amp transformer and have a fan mounted in the area of the heat sinks of the output TIPs. Wire up the common grounding at all the boosters (I use the mounting nuts on the back of TIPs Q7 and Q8). This grounding should end up at a true earth ground - you'll not have any over voltages then. The EasyDCC doesn't have reverse loop short sensing and switching in the boosters - so I recommend using modules - the Lenz units are great since they sense for a short on both rails and switches with either one being shorted. That make for safe and fool proof reversing loop actions.
-- Ed McCamey (email@example.com), April 19, 1999.