so i am using atlas undertable switches… and i wanted to make sure i had the right idea
i am going to use SPDT on-center off-on switches… i wasnt planning on using momentary switches, because i can just flick it on and back to center and get the same effect right??? … anyway to wire this, i should wire from my powersource (via my terminal block) to the center terminal on the switch, and from this center terminal on the switch i should wire to the center wire of the turnout… also from the left terminal of the switch to the left terminal of the turnout and the right terminal of the switch to the right terminal of the turnout…
No thats not right, one terminal goes to the SPST switch, and the other goes to the switch machine common ground . You SHOULD probably buy momentary contact switches - on the off cance you forget to put the switch back to the “off” position, you will have a burned out TO motor faster than you can say “Atlas”.
like this:
SPST:
0 ----- (green wire from switch machine)
0 ----- (to power pack)
0 ----- (red wire from switch machine)
In short : No. The wiring should be done as follows…
The center terminal of the switch is connected only to one terminal on your power source.
Each of the outer terminals on the switch is connected to one of two outer terminals on the motor.
The center terminal on the motor is connected to the other terminal on the power source.
When you buy the SPDT (center off) switches, be sure to get the ones that do spring back to the OFF position. (IF they exist, they might be labeled as “normal OFF”.) If you plan to rely on people quickly snaping the switch back to the OFF position, you can also plan on replacing the Atlas motors on a regular basis. Murphy’s Law dictates that someone will either forget or accidentally knock the switch on and burn out the motor.
If you can’t find such switches, you will need a momentary “normal OFF” switch wired in series with the wire coming from the center terminal of the motor (ie: between the center terminal of the motor and the power source).
An alternate option is to install a capacitor discharge unit (CDU) (instead of the mometary “normal OFF” switch) which will only allow a short burst of power to be sent to the motor.
I am using these same machines to operate turnouts on my N-scale layout. However, I am using SPDT “on-on” switches in combination with a momentary “normal OFF” switch. I wire them exactly as I described above.
Another vote for momentary-contact toggles. It’s particularly important when you’re using under-table switch machines. If you’ve got plain center-off toggles, sooner or later you will burn out a switch machine, and it will be a pain in the caboose to replace it. Take a look at on-line places like www.allelectronics.com for the toggles. They’re about 50 cents each for the miniature ones.
I also second the suggestion on the capacitive discharge unit, or CDU. This will give a bigger “kick” to the machines initially to throw the turnouts better, and then it will protect the machines by limiting the current going through them. I built mine for a few dollars in parts from Radio $hack. If you’re “afraid” of building your own circuits, this is the perfect small project to get over that fear. It’s only a few resistors and capacitors, and one diode bridge if you want to feed it AC instead of DC. Or, you can go buy a unit like a Snapper.
i found spdt switches that spring back to center off… so i am set… and now that you all got me straightened out about the one wrong wire i should be having my turnouts firing tonight!
I don’t understand, please explain why this (requiring three switches) is better than just using a single SPDT switch for each turnout (requiring only two switches)? Except maybe for an instance were two switches need to work together (like a crossover) I am not understanding the advantage.
I think that’s the point. you can throw multiple switches at once. if SPST switch 1 and 2 is on, throwing DPDT switch left or right will set both TO’s to either the diverging route or the through route…
That’s it exactly! There can be more than 2 turnouts on 1 DPDT in this design. I’ve had as many as 6 on one on a previous layout. You have an on/off switch for each turnout so only the turnout(s) that’s turned on trips. It’s a very simple and basic design. I’ve used it for years without a problem.
