I ran into an interesting problem as I was trying to enhance my layout by adding some dwarf signals to indicate the position of select turn outs; red when the turn out is diverging, green for mainline. I am running TMCC, with the switches controlled by an SC-2. The SC-2 is configured to run 4 switches with the remaining two terminal blocks set up for accessories. The SC-2 is using the first switch block for power, i.e., I am not using the wall wart nor external power connections. Each switch’s common terminal is tied to the C terminal of a 1033 (16V) which is thereby powering the SC-2 via the switch tied to block one. The switches are Atlas Super O.
Here is a diagram of the configuration with everything working:
I am only showing one switch, however, all four of center / left terminals are hooked to other switches identically to the one shown.
I decided to use Atlas Snap Relays to control the aspect of the dwarf signal. They are similar to the switch machines in that the are a solenoid with a common tap to the center of the coil and two connections to each end of the coil. Completing the circuit on either end move the core toward that and sliding some internal contacts. I wired them per the Atlas directions. The result looked like:
You seem very knowledgeable have an interesting electrical problem. I am not qualified to solve the electrical isse but would offer the following.
dz stuff does offer Atlas compatible switch machies. changing to them could become a sizeable investment [$s and time] even for only four switches. basically, as you will see from their website, a switch machine and a relay are needed to manage the application you want – drive the switch and activate the dwarf signal. It will work fine. i use it with ross/gargraves.
an all in solution --dz2500 (+/- $25), a dz 1008 relay (+/- $9) per switch . you would also need a dz2001 databus driver (+/- $25) and the wire for the bus…and the time to do it. they work well with SCs and ASCs.
They have a couple of other products as well that you may want to investigate—like a dz1011 that look and work like dwarf signals but are optical sensors --like lionel’s 153ir – with a much smaller footprint.
I would consider using the atlas, the way it was, without the “snap” relay and pick up the dz 1008 relays and operate the signals you already have with isolated rails.
I am using a setup almost exactly like yours, but I use the snap relays to control 10 amp power relays to power the track as I change routes with the switches. I use an 18 volt tranformer to power the switches and snap relays which puts out 4 amps. It is protected by a 5 amp CB.
One thing that I read on a few forum posts is to never use the #1 terminal on an SC2 as it creates problems due to some internal wiring. I use the wall wart to power the SC2 and have never had a problem with this setup.
One additional note, you can change the #5 & #6 position on the SC2 to momentary contacts and connect switches these positions so that you can control 5 switches with each one without using term #1
If you want more info on this do a search on SC2 or SC-2 on this forum or go to the other forum and search the TMCC section. There has been a lot of discussion on this subject.
Your wiring diagram looks OK to me. The difference in resistance between the snap relay and the switchmachine, I think is due to the fact that the snap relays are actually modified HO switch machines and the coils are probably wound with smaller gauge wire. This would account for the difference in measured DC resistance. As you mentioned this is not really relevant to AC operation.
Good luck on solving your problem, hope I have been of some help.
After thinking about your problem a little, I may have overlooked the simplest explaination. Do you have other loads connected to your 1033? The problem may be as simple as not having enough power available to meet the inrush current requirements of two solenoids operating at the same time. If your fuse is a fast blow variety, I don’t think it is large enough.
I do have the variable outputs on the 1033 in fact tied to a 10V bus on the layout (the 16V for the relays and switch machines are pulled from a fixed post). I have two SC-2s and a Gantry Crane tied to the 16V bus. On the 10V bus I have a blinking water tower, fueling station and ice house. During my testing, nothing was running on the 10V bus – I was only testing the switches. But I can check the current draw on the 10V bus to make sure of this, or even completely disconnect the 10V side. I seem to be pulling a steady ~170mA on the 16V bus with nothing operating – I suspect this is power for the 2 SC-2s.
Also, I thought it may have been a voltage issue as the switch machines and the relays are listed for 16 – 18 V. I tried a Lionel accessory transformer set to 17V (I believe it can provide 30W). That would only be about 2A and I believe that you said your set up was pulling 4A for both. I suspect that it could be too much for the accessory transformer thereby negating my test, but I suspect that a lone 1033 should be OK. However, the 1033 is a new addition for me as of last Monday, but I would think if it is supplying 16V everything is well with it and it could handle the amperage – but I am not that familiair with the 1033.
I was able to do some further testing this evening. I removed the power / switch connections from the #1 terminal of the SC-2 and used the wall wart. Still no luck, the switch machine was very lethargic. I then tried a CW-80 and both the switch and relay moved as they should. The switch was not moving to the full extreme but it was locking the points in place. The Atlas switch machines are funny in that they do not need full throw to lock the points based on the internal slide mechanis.m
I then decided to do some more testing with the 1033. I had it plugged into an APC surge protector / power strip combination. I tried various plugs on the strip and also directly to the wall. When plugged into the wall the switch seemed a little peppier but it was still not moving fully. I then attempted to disconnect the 10 volt bus from the A – U terminals on the 1033 and the switch seemed to move even more, but still not to the full extent and definitely not locking the points. I reconnected the A – U terminals and made sure there was no current being drawn. Showing 0 A on the 10V bus, I still got lethargic performance and only partial travel on the switch.
So it looks like the 1033 was the problem in this case. It just did not have enough current push. It was worse when there were connections to the A – U variable posts even with no draw. So I guess I will be going back to the CW-80, which the 1033 was bought to replace!