clockman

As promised an update on this project: In short, yes, it works fine. First my kit: I’m using old materials recovered from my late uncle’s finescale layout. Track is Scaleway and the custom 5 point matrix is, I believe, Marcway. Point motors are Peco SL10s which I have re-pinned with longer pins to mount below the track board. CDU as stated earlier ECM. Distance between controller and control panel 2 metres. Distance between control panel and layout board 2 metres. Issues you raised for consideration: Matching point motors: I used a pair that matched to better than 0.1 ohm Relays: The relays are Hongfa PCB mount latching signal relays part number HFD2/005-S-L2 mounted on Vero board strips under the board and near the poin t motors. While the spec says 5V coil I have used them in my earlier layout with no problems. The CDU output port measures 23V but without an oscilloscope I cannot measure the spikes. The relays have an adequate switching spec and are available from RS components at under £3 / pair. Ohms law: I have used standard alarm cable (7/.02) but have stripped the wires out of the sheath and doubled up on all signal wires - so now 14/.02. The 25 way D lead between the CP and the track board has 2 pins allocated for the common returns to minimise loss due to the lead. The result is a solid 'clunck' switch with no hesitation and I have reduced the signal wire count to a single 25way lead with a separate 6pin Belkin lead for the track and auxiliary 12v lines. 12V wires also doubled to 14/.02. (Belkin was a great little connector now no longer available. Used them in my youth…a while ago!) So, thank for your inputs. Result achieved and remaining track layout now proceeding! Pictures, circuits and other info can be supplied if wanted.

Thank you all for very useful feedback. I will take it all on board and report the outcome in due course - which at the present rate might be a little while!

Thanks Ian. The relays are latching types so once triggered they stay switched. I note your comment on the relay parameters, though! Martin Ballard

In my original layout I have used a CDU unit to switch a pair of points together. This works fine. I am now ‘tidying up’ the whole layout as I embark on the next building phase and am trying to reduce the wire count. So my question is: ‘Can I use a common wire from the point switch (fed from the CDU) to feed both the point motor and the separate relay that switches the frog feeds’. I will provide a common return from both the point and the relay as well. I am concerned that i) the CDU spike might damage the relay and ii) the CDU might not switch the points with the extra load The CDU is an old ECM unit with a 3900 microfarad capacitor fed from the 16v a.c. output from my Gaugemaster DF controller. At the moment, the CDU happily switches 2 points together but I use a separate 12v supply for the relays. Thanks for any input in advance!