Atlas switch machine

Discussion in 'FAQs' started by Freelancer, Nov 6, 2002.

  1. Freelancer

    Freelancer Member

    I have some Atlas under the table switch machines, which seem to be working fine, but when I hook the machine to the table and track, it won't switch the track, it will attempt to move, but it doesn't succeed. Someone told me that it might not be getting enough electricity, but I am not sure. Any help would be great. Thanks.
  2. Wyomingite

    Wyomingite Member

    Atlas switch machines

    Hi Freelancer,

    I don't have any under the table Atlas switches but not enough power could be the problem. I control my switches with a seperate power pack and there is a distint snap when I throw them. Using the same power pact that I ran my trains with I could barely here them throw. Another thing is are you sure you have them wired correctly? Have fun Ron ;)
  3. Freelancer

    Freelancer Member

    Thanks Ron, I am pretty sure that they are wired right. I followed the diagram on the box, and I got them to work without the track and table. I haven't been running any trains when I switch the machine so all of the power from the transformer is available, but I do like the idea of using a seperate transformer for switching, thanks.
  4. 60103

    60103 Pooh Bah

    Freelancer: Can you throw the switches manually? I think there is a little plastic slide on the machine that should do the job. If that works, then you should look at the electrics.
    Did you hook up to the AC terminals on the power pack?
  5. Three questions:

    1. Is this happening with all of the switch machines? A few of them? Only one?

    2. What size hole did you drill through the bench work/subroadbed? (I occasionally have had to drill a slightly larger diameter hole than called for in the mounting instructions)

    3. Did you use ballast and/or ballast cement in the turnouts?
  6. Freelancer

    Freelancer Member

    I can throw the switches manually just fine, and they work just fine with power. But when I connect them to the switch track, they just don't have enough umph! Unfortunately this happens with all of my switches. I have drilled 3/8" holes for them and I can look down the hole and see that there is nothing interfearing with the switch, and I haven't put any ballast on them either. Is it possible that the track has put too much stress on the switch? Is there any way that I can make the track slide easier?
  7. cidchase

    cidchase Active Member

    Hi Free,
    The turnout should switch freely with almost no force, make sure there's not glue under the throwbar or some other contaminant.
    The operating pin must not put any stress on the throwbar except sideways when throwing the turnout. Make sure its on center also.
    How thick is your table? How much voltage are you using on the switch machines?:confused: :confused: It's puzzling
  8. Freelancer

    Freelancer Member

    There is nothing in the way, and I can't really tell if there is much stress on it. The table was too thick to go through, so I am putting the switch, directly under the track, and cork. I am not sure how much current I have going to it, but I am using a Bachmann transformer, that came with some of my early train sets. The output is 17 VDC 20 VAC. Not that I know how much is actually being used. Do you think that my transformer is my problem?
  9. Gary Pfeil

    Gary Pfeil Active Member

    It could be the power pack. That 17 volt dc output is probably without a load. Twin solenoid type machines have little resistance, therefore draw significant current when operated. The voltage is probably taking a nosedive when the coil is activated. Those train set packs probably can't support even a 1/2 amp at their rated voltage.

    Another possibility is the turnout is fastened down to securely to the roadbed, creating friction on the throwbar, making it harder to throw.

    Just a couple thoughts.

  10. tomfassett

    tomfassett Member

    I would test the lack of current idea before making any changes. I suspect your problem is with mechanical resistance in the switch, or electrical, between the pack and the switch. Take a switch motor that is not mounted and attach a similar amount of wire (whatever length you have to the farthest switch). Hook it up to the pack and see how it works. As others have said, there should be little "drag" on the solenoid from the switch.

    Here is what I would do.
    1. Mount a switch on a piece of scrap and install a switch machine to it. Attach a very long wire to it and see how it works. If it operates fine with a wire feeder longer than anything you have, the power is sufficient.
    2. Check the alignment of the switch machines to the throwbars. If possible, put a piece of metal tubing in the hole to make sure the shaft is not touching a rough surface or catching on wood fibers.

    As for mechanical resistance, I have gotten into the habit of grinding down any surface right below where the throwbar is located so there is no contact between the roadbed and the throwbar. Even a minor amount of friction can cause problems.

    Try the "long wire" test and verify if your power pack can produce enough current to overcome the voltage dropping (resistance) properties of the wire. If it works, the problem is mechanical.

    Tom F
  11. Clerk

    Clerk Active Member

    One suggestion. Try one switch with a capaciter. The capaciter should give it the sudden jolt it needs. If it works, there is your answere and you can fix the rest of them. Also if it works, your transformer does not put out enough amps.
  12. tomfassett

    tomfassett Member

    To use a capacitor, it would need to be before the momentary switch that fires the solenoid as it would need to charge from a constant supply before discharging. If a large enough capacitor was installed after the momentary switch, it would actually take energy away from the solenoid (as it charges) if the momentary was held for a short period of time. The idea of using a capacitor is a possible solution though, as a sufficiently large capacitor placed across the leads of the power pack output would help reduce the voltage drop (momentarily) due to the sudden current draw. Before I would try to make modifications to allow the small transformer to act more powerful, I would be inclined to get a more powerful source. You could build one that would supply 2 amps for under $20 with parts from Radio Shack. If you do want to try a capacitor, get one rated for more than the output of the power pack (50 volts DC would suffice) and get the biggest monster you can (something in the 3000uF range or higher). Anything smaller would not store enough energy to make a difference. Better yet, stick a few of them in parallel for higher energy output. But, as stated before, you are approaching the expense level of building a better power source...
    I have attached a schematic for a simple supply which should be able to fire any switch machine with a reasonable cable length (under 100 feet). I have a couple of these located around the layout that I use to power switch machines using relays from a master control board. Feel free to ask for clarification if you don't understand the schematic.

    Tom F

    Attached Files:

  13. Clerk

    Clerk Active Member

    You are right of coarse. 20 years ago I probably would have remembered to include a schemetic showing how to wire it up. I used to be in electronics years ago and have designed many schemetics for my own use. When I had my first layout I designed my own controller with step up power from pulse to straight DC for better slow moving and control. This was before the model train manufactures started to incorperate them in their transformers.
  14. tomfassett

    tomfassett Member

    Did you design your own throttle or build the one that was featured (over a few months) in Model Railroader (back in the early 1980s)? I built that unit and it worked great (still does although I don't use it much any more...). Its nice to find someone else who dabbles in electronics for modeling purposes. There are a lot of great little projects that can really "spice" up a layout. I would like to see a forum section dedicated to this...

    Tom F
  15. Clerk

    Clerk Active Member

    This was way back in the early 60's before most of the model magazines came out. I had bought a transformer to run my trains with and was so dissatisfiedkl with it that I took it part, Took the transformer out and used that as a base and built my own. I baught the diodes and reostat with a knob,a thin sheet of luan for the top plate and ended up with a square box about 4" X 4". The transormer took up most of the space. It worked like a dream. When I had to move I gave everything away to friends. I sure wish I had that controler:(
  16. tomfassett

    tomfassett Member

    I wish you still had it too... I would have liked to have seen it!:D
    Boy, building a transistorized throttle (like I built) in the 60s would not have been cheap as transistors were expensive then. I remember paying $8 for a Phillips version of a 2N3055 power transisor in the early 70s. Today you can get them for 10 cents if you look hard enough. Radio Shack has them for (I believe) under a buck (and that's todays dollars...):D So what did you use for the pulse circuit? Transistors of something else? I suppose one could have easily used an oscillator tube in a similar fashion, coupled with some kind of output current controller (tube or transistor). It would have been pretty rough to build something similar to todays pulse throttles without the ease and availability of semiconductors.;)

    Tom F
  17. 60103

    60103 Pooh Bah

    I think the original pulse power packs were made by switching out one side of a bridge rectifier; that gave a series of humps in the voltage separated by flat spots of 0V, instead of a full set of humps. A switch or variable resistor would allow the rest of the current to be brought in as pulse power was believed to heat up the motors. Very few people did anything further to smooth out the current.
  18. tomfassett

    tomfassett Member

    Ugh! 60 pulses per second would cause chatter like no tomorrow!:D That is one idea for non transistor throttles... Though without an amplifier, I can't see a way to increase or decrease (as they work now) the pulses logarithmically as the DC increased. I guess you could have let the full voltage pulses mix with the DC, but that would have created different acceleration and speed curves for different pieces of equipment, as well as limiting the low end speed. Not that it matters so much now, but I find it interesting to see how the current "technical standards" of the hobby came about. Personally, I think Dick has some of the answers as he was into building these throttles before the current "state of the art" was developed. C'mon Dick, how did you do it?;) :p

    Tom F
  19. tomfassett

    tomfassett Member

    Um, so now that we have gotten off track on a discussion of the history of electronics in model railroading,:D has Freelancer ever solved his problem with the errant switch machines?

    Tom F
  20. Clerk

    Clerk Active Member

    Tom. Sorry for the delay. Got busy. I used 1/2 of the rectifier bridge with a variarble resistor and believe it or not it worked pretty smooth with no chatter.

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