Siding with live frog points

[Neil Robinson]

I`ve not used live frog points much but I`m in the process of fitting them to my local GSS group`s layout. This layout needs to be suitable for both analogue and digital operation so sidings and loops have isolating switches.

I`ve only just realised that the frog polarity switch can also do the job of an isolating switch (making the siding self isolating) on analogue if I omit the usual isolating gap between the live frog and the siding rail connected to it. With the point set for the siding each rail is connected to its appropriate side of the power supply but with the point set for the main line both siding rails are electrically joined and connected to one side of the power supply. There is therefore no potential difference between them so no power.

My concern is that I doubt it can be that simple and I wonder if there`s the possibility of damage to sensitive electronics, especially the digital systems.

What potential (sorry about the pun) problems am I missing?



I`m aware of a problem MTH`s DCS system, namely interrupting the supply (other than very briefly) and then restoring it without resetting causes the loco(s) to revert to analogue mode. They then see the full track voltage and set off at high speed!

 

[beavercreek]

Hi Neil
I think your idea has it nailed
I have a few of the Aristo/USA trains No6 switches(points) and they have live frogs ( well they are until I run 22V at 10 amps through them, then they look decidedly ill !!.).
The wiring is very similar to what you have indicated, only difference being that they use a micro switch to change the supply to the preferred route.

 

[ntpntpntp]

Surely it's no different to placing a DCC loco on the track and turning on the track power? The loco doesn't (usually!) go bang or zoom off when power is applied. Just make sure the DCC system speed is set to zero for that loco before switching the point to the siding.

One drawback of cutting the power on the siding is if you have a sound-fitted DCC loco the sounds will cease unless you've got a huge power buffer. This is why I prefer to stick with isolating both frog rails and powering the siding via it's own SPDT switch - this way you can leave the power on when running on DCC and switch the section off when running DC.

My entire garden line is wired as if for DC, though 99% of the time it's running under DCC so I simply leave all sections on.

<edit> Are you worried about effectively shorting the input to the decoder when both rails are the same polarity? I don't see how it could be a problem, as smoothing capacitors etc. will be the DC side of any rectification and unaffected by the short. I've never seen any problems. </edit>

 

[Deleted member 1986]