TomJ Posted May 10, 2015 Share Posted May 10, 2015 This might be a daft question - with either a resounding 'of course' or a 'don't even think about it' answer but I thought I should ask before connecting wires a blowing things up!!! My short shunting DCC layout uses a NCE Powercab for the trains and peco point motors operated by conventional switches. For improved reliability the point switches are fed by a CDU and this requires a 16v AC supply. For a temporary bodge I've 'borrowed' a simply analogue controller from my sons trainset. However this isn't a very elegant solution as currently this is balanced on the layout (and next time he wants to play Thomas he'll notice and want it back!!!). As my DCC is 16v AC could I power the CDU from this - ie connect the CDU input to the power bus?? If it's a capacitor then does the actual current matter? After all on my other layout I use Dcconcepts decoders, with inbuilt capacitors powered from the DCC and they work fine. If I try this then what's the worst that could happen? If not is there a cheap, simple alternative? I don't want to buy a DC controller just for four points! Thanks Link to post Share on other sites More sharing options...
hayfield Posted May 10, 2015 Share Posted May 10, 2015 Go to a local show, yesterday plenty available on traders stands at Watford and I guess all other shows will be the same. They were at reasonable prices. Link to post Share on other sites More sharing options...
GoingUnderground Posted May 10, 2015 Share Posted May 10, 2015 Then buy a 16V AC power supply unit from Maplins or Conrad and use that as the power source for the CDU. There's no point in buying a controller when all you want is a 16V AC power supply. Link to post Share on other sites More sharing options...
gwrman Posted May 10, 2015 Share Posted May 10, 2015 Could try one of these:- http://www.train-tech.com/index.php/points-control/pc2-quad-point-control Nigel Link to post Share on other sites More sharing options...
Crosland Posted May 10, 2015 Share Posted May 10, 2015 It really depends on the design of the CDU. Faster charging ones will draw more current when charging. Crude ones do not isolate the input and output when fired. I would just try it and see, you will certainly not do any harm. The other point to note is that DCC is a square wave, so your 16V track voltage is also the peak voltage and the voltage that the capacitors will charge to. A conventional AC supply is specified by the RMS voltage. The peak voltage to which the capacitor will charge is approx 1.4 times this, so around 22V for 16V RMS, giving more oomph (that's a technical term ) for the point motor. Link to post Share on other sites More sharing options...
RMweb Gold traction Posted May 10, 2015 RMweb Gold Share Posted May 10, 2015 This might be a daft question - with either a resounding 'of course' or a 'don't even think about it' answer but I thought I should ask before connecting wires a blowing things up!!! My short shunting DCC layout uses a NCE Powercab for the trains and peco point motors operated by conventional switches. For improved reliability the point switches are fed by a CDU and this requires a 16v AC supply. For a temporary bodge I've 'borrowed' a simply analogue controller from my sons trainset. However this isn't a very elegant solution as currently this is balanced on the layout (and next time he wants to play Thomas he'll notice and want it back!!!). As my DCC is 16v AC could I power the CDU from this - ie connect the CDU input to the power bus?? If it's a capacitor then does the actual current matter? After all on my other layout I use Dcconcepts decoders, with inbuilt capacitors powered from the DCC and they work fine. If I try this then what's the worst that could happen? If not is there a cheap, simple alternative? I don't want to buy a DC controller just for four points! Thanks As the CDU (GaugeMaster) I have is 16-24VAC input, I did exactly what you're asking! I'm using a Bachmann EZ-Command which has the 16vac 1amp transformer. Measuring the output wires from the EZ Command to the DCC power bus it measures about 20v AC drops to a huge 19.7VAC when one loco is running with lights on!! So I just connected the DCC power bus to the input of the CDU seems to work fine, with no noticeable effect on the running loco. I know the PowerCab output to the rails is much lower than this, so it might work depends on the CDU. Cheers Ian Link to post Share on other sites More sharing options...
Suzie Posted May 10, 2015 Share Posted May 10, 2015 Most off the shelf CDUs have rectifier diodes on the input that are only suitable for industrial frequency AC (up to 65 Hz) and are not suitable for DCC frequencies (beyond 10KHz). Connecting one up may give you the impression that it is working, but the peak voltage available from DCC (usually around 15V or so) is a lot lower than the peak voltage from a 16V AC transformer (25V or so) so you will get a lot less power to your point motors. If you check the temperature of the rectifier in the CDU you will notice that it is getting very hot, and if you try to run a few trains you will notice that there is a lot less track power available and the booster will overload a lot quicker (and in some cases will refuse to start up if it is very sensitive). The only CDU that I know of that will take a DCC track feed as its supply and give a reasonable output is a kit one that is quite easy to make and cheap. Alternatively just buy a 1A 16V AC transformer or 1A 24V DC switchmode PSU for your existing CDU. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.