During the summer I spent time woodworking. Now that it’s getting colder in the garage, I got back to my HO layout.
Just finished converting layout to DCC using 5 amp NCE Cab Controller. The layout was DC with 8 blocks. Because I still have some DC I found a way to have the layout either DC or DCC (but not both at the same time). I did remove the block switches and tied the block wires to a 14 gauge bus.
My father was an electrician so I inherited some of his stuff. I found a 3P3T switch that was for motors. Two of the poles go to the track and select either DC or DCC output. The third pole is connected to the 120v hot to go either to the DC controller or the DCC NCE controller. In the center position both controllers are off.
My turnouts needed A/C and I didn’t want to use the DC controller’s A/C connects especially when power was to the DCC controller, so I installed a doorbell transformer using the 16V 10AV setting. Works great since I have 2 turnouts as a transfer between 2 track loops.
The layout has a master switch. The layout also has buildings lit by either a Dwarvin fiber optic system or small LED’s power by an old 3v transformer. Like my dad I save old electronic components. Never know when you might need them.
I did a similar thing. My layout is in three power blocks; the original section is switchable between the old homemade DC system and my NCE. I’ve only switched back to DC once, to test a new engine. I don’t really even need to do that because I have a small side layout that’s still DC.
The NCE booklet has a way to install a programming track with a DPDT switch, but how often would I use that on a 4x8 layout. I had a 26" DC test track already that I didn’t want to convert to the programming only by changing the connectors.
So leftover alligator clamps and stiff solid wire came to the rescue.
On the NCE, programming on the main will not do everything that you can do on aprogramming track. So I do most of my programming work on the programming track. I don’t think it’s that big of a hassle to move the locomotive back-and-forth.
You have 120V and track power on the same switch in the same enclosure?!? Am I reading that right? That is both dangerous and surely illegal if that’s correct.
Switching should be done on the low voltage side only.
The switch is a 3P3T originally for 120/240 v motors with the poles isolated. You can’t find this switch at Menards or Home Depot. It might have been used on an EMD locomotive. The tracks are on 2 poles so no connection to the wall voltage on the 3rd pole and no crossover.
I would highly advise against it. Not only does it not really make sense in the first place, but you should NEVER be mixing line voltage and track voltage in the same box even, much less the same switch. Maybe the change of them crossing is remote, but I would want ZERO chance, which you can’t guarantee. It also sounds like a liability and insurance nightmare.
There is never ZERO chance of something. Not even in a power pack, where track voltage is in the same box as the 120v supply. A faulty power pack could charge your layout with 120 volts, and has just as much a chance of doing so as the 3P3T switch. Simply following a general rule-of-thumb and applying it like a blanket to all situations is absurd. As an experienced autodidatic electronics engineer, I can tell you that one has to consider matters on a situational basis. No matter how you wire something, no matter how many precautions you take, there is never zero chance that something will not go wrong. You can’t guarantee your layout’s safety any more than this, can you?
Sure, I suppose if you want to be pedantic, there is an absolutely tiny non-zero change that a power supply could spectacularly fail and output line voltage instead of 15VDC or whatever it is supposed to put out.
However, those are certified and safety tested, and built specifically NOT to do that, versus someone wiring 120VAC through a switch that’s also carrying track voltage, which is just plain irresponsible and dangerous.
Certification is not a substitute for design. And good design is entirely separate from certification. A well-designed circuit, whether certified or not, is completely safe and responsible.
