Basic pushbutton questions

Since you obviously don't have more than 5A from that HO power pack, I can't see why you need large switches.

I use the C&K mini push-buttons, they're easy to push, and they come in all flavors, including DPDT.  If you don't like the "naked" look, countersink the mounting hole in the panel.

Right, sorry. I should have mentioned that I would like a little more power, and will likely upgrade at some point soon.

Which specific C&K switches are they? I am seeing a wide variety on their site. Thanks!

These are the ones that I use: C&K Push Button

These seem to fit your requirement for a flush mount switch: C&K Flush Mount Push Button

Since nobody has said it yet I will throw the usual caveat in. 99% of all the equipment mententioned in this forum is designed to operate on AC voltage. Some of it will run on DC and some of that will run quite well on DC. HOWEVER, some of the equipment available will not run on DC and may even self destruct if forced to do so. If you desire to run your equipment on DC make sure you understand this difference and make sure that any equipment you attempt to run on your layout is capable of operating on DC.

Al

Johathan,

I was just going to post a topic titled "Can I run an engine on DC?" so this is great!

I have a new PRR 0-8-0 and a K-line MP-15 that I would like to try running on DC.  Does anyone know if this will work.  I don't want to wreck the locos.  

Jonathan,

Could you explain more how those switches work to reverse the loco?  

 Take a look at this conversation that I started a while back.

 I can't imagine how you would wreck them. What is most likely to happen is that the whistle or horn will sound constantly, as these features are triggered by DC. Are you able to switch off the whistle or horn? I have a switch on my Docksider for this purpose.

Three-rail O-gauge engines are usually reversed using a (1930s-era, I believe) technology that cycles through various modes every time the power is cut to the engine. That is what the direction button does on your transformer. Since zero voltage is neither DC nor AC, it works the same on either. I would use the SPST switch to do that. It is not necessary to add an additional switch, I just want to do so in order to avoid fatigue on the power pack. And it is more convenient than turning the dial to zero every time we want to cycle the reversing unit in the engine.

The DPDT switch is used to reverse the polarity, which triggers the whistle.

I like DC because my particular engine runs more smoothly with it. Why did you want to use DC?

Jonathan

Older locomotives with mechanical E-Units will generally run on DC, though as mentioned, if the polarity is right, the horn will sound all the time.  Engines with electronics will frequently NOT run on DC, though some will.

Reversing the polarity will likely cycle the E-Unit as well, something to test.

I don't think the whistle and bell work the way you think. I believe the whistle is sounded by passing +5 volts DC on top of the ac transformer voltage. To sound the bell -5v DC is used instead. Someone may correct this but I think I'm right.

Ron

I've truthfully never tried DC running, the old PW whistle relay will most likely trigger on either polarity of DC.  To make it work for only one polarity, you'd have to add a diode.

Thanks, Ron. Your message made me go check it out with my multimeter. This is what I found:

When I have the whistle enabled, there is one polarity that no matter how much voltage I give it, there is no whistle (I presume that if I had a diesel, the horn would sound at this polarity, however). When I switch polarity, the whistle sounds at 5V and above. Does that sound about right?

I can only vouch for this behavior on the Docksider.

Regards,

Jonathan

Is that an electronic whistle or a mechanical whistle.

It would certainly seem easier to just pick up (or borrow) another AC transformer in the interim.

electronic

The electronic whistles are polarity sensitive, that's why it only works with one polarity.  Mechanical ones would whistle all the time with DC.

Yes I believe GunnerJohn is correct on the postwar mechanical whistles. On the electronic whistle there is a bell on some of them. The positive pulse triggers the whistle and the negative pulse triggers the bell. If memory serves me right the Docksider's electronics do not have a bell so it wouldn't do anything when the polarity is reversed. I haven't had mine out in while but I think that is correct.

Must be, or the bell would be ringing away when the polarity was reversed!

You could use a 12 volt DPDT  relay with a 7812 regulator circuit and run it off track power. This would work from about 8-18 volts on the throttle maybe even a bit lower.

The lionel electro-mechanical whistle relay is for low voltage around 3volts DC and does not pass AC. It may overheat with straight DC at 18 volts. As John mentioned it would blow the whistle with either track polarity. The mechanical E unit is also an AC coil. It will have much less impedance run on DC and prolonged use at higher voltages could overheat it. The PW type motor itself will run on AC or DC. Installing a rectifier and capacitor in series to the motor will make it run smoother and give better low speed performance. This rectifier can not be fit in some steamers.

Some PC Boards can be damaged by straight DC while others are not. The K-Line external,bell/whistle controller used a bridge rectifier and capacitor so straight filtered DC was sent to the track when the button was pushed. The lionel external controller (one design anyway) uses 6 diodes in one direction and one in the other so the sine wave is unbalanced only by about 3 volts more positive than negative or negative than positive depending on which button was pushed.  So Lionel did not like the simpler K-Line design perhaps fearing damage to the solid state boards.For solid state boards the whistle will sound on one polarity and the bell if equipped will sound in the other.

Here is one way to make an external bell/whistle controller. Works best with pure sine wave transformers. If relay contacts are used in place of push buttons, the whistle/bell can be automated to blow at a crossing approach for example.

http://www.jcstudiosinc.com/Bl...2&categoryId=426

Dale H

Thanks Jonathan, that is helpful information.  The K-Line loco doesn't have a horn or bell - who knew that could be an advantage!

I am interested in playing with some electronics circuits and micro controllers and most of what is written seems to be for DC.  So I thought it would be useful and fun if I could just swap out the power when I wanted to experiment without having to permanently change the wiring in the locomotive.

In case anyone wants is interested, I just happened to see that Jim Barrett did a piece on the bell/whistle controller in Run 199, titled "Old Transformers to New Transformers: Important Points to Ponder"  In the article he shows the full sine wave shifted to a "Plus" (his word) offset to trigger the whistle and a "Minus" offset to trigger the bell.  I think that is what others have said here but I needed to see the graph to wrap my brain around it.

Phil

Hi Jonathan, I have much experiance with all this & can answer with certainty.

    I've personally done all this with my own stuff.

      Regarding the switches, 15a @ 20v is best due to they can take a full short & usually would not suffer damage. Your transformer is not that large so the smaller ones would work, but I would use the larger. Now... look at the rating of a switch. If it's rated 5a @ 40v, that would handle 13a @15v. That will be a guide when looking for switches.

    Ok, regarding the push button to reverse trains, you need a NC (normally closed) momentary switch. Of the above rated amp. Personally, you may be better off with an old Lionel reverse switch #88C. Here's the item # on Ebay so you can see what they look like. #360367163071.  Now.. Most important you check # on switch. There are switches that look the same, but the contact is opposite. Those are for activating accessories. The # on case is what you must see to get correct one.

    The loco reverse unit whether old postwar or modern is triggered by interuption in power. No matter if powered by ac or dc.

    Regarding dc power. I have postwar, modern, Lionel, Williams, MTH, Kline. All run & reverse well on dc.

 Now... Very important to understand the whistle/horn/bell controls.

    All the whistles/sounds are triggered by dc... Postwar with the old whistle relay is triggered by dc, but not sensitive to polarity, either + or- triggers equally as well.

   Ok, on modern sounds with electronic controls polarity is most important. Again it's dc. Horns/whistles need + to center rail. Bell, or any other operations like coupler open that use bell button gives - to center rail. Yes, that means track power feeder wires must be on correct rail!

   Now that brings us back to powering trains with dc.. Postwar will sound whistle/horn continuously. Electronic sounds will activate continuously or not at all depending on if + or - is to center rail. The train will "see" any dc as a signal to activate sounds.

    Now, some of the cheapest Lionel from late postwar/early MPC was actually dc only motors. They cannot run on ac & didn't have sounds. If you run a dc motor on ac it will simply vibrate/buzz. Usally no damage. To get the modern dc can motors to run on ac there are electronics inside the loco to convert ac track power to dc motor power.

    Let me restate, I've ran all my locos on dc. The ones with sounds will sound constantly or not depending on if + or - to center rail. They all ran well & reversed normally, just the sounds was the issue. (dc power can magnetize the eunit plunger over time-that can be an issue, but that's another subject).

     All your trains should run well on AC. You didn't say what transformer you have. I'd like to know that.

    You don't say exactly what other locos you have so I don't know how much power you need. I wonder if a good used CW80, (the later one with the G prefix) would be a good choice for your needs? They have 3 buttons on top. Reverse, whistle, bell. They have a fast acting circuit breaker with warning light. For smaller outfits they have enough power. If you get into a 2035 loco & larger the power is not really enough. A postwar LW is one of the nicer transformers. Lots of power & also has reverse button.

    I've ran some small lionel on HO power packs (like the 1060). Will go, but not enough power. If you go more than the Docksider, you'll need more, much more power. Forget the HO transformer.

     Very best, Don Johnson

IMO, there's some bad information here.

First off, switch ratings are almost always for AC unless specifically stated that it's a DC rating.  AC switching is easier on the switch due to the constant switching of the current where breaking a DC connection always involves the maximum current flowing in the circuit.  Typically, a switch DC rating will be less than the AC rating, how much less will depend on the switch design.  A DC inductive load aggravates the situation due to the fact that the field collapse or back EMF can be in the order of several hundred volts higher than the applied voltage, this can exceed the insulation resistance rating of the switch, tracking or arc over can result.  This is the situation with electric motors, say the ones in the train we're talking about.

Second, it's not total power that is the limiting factor, it's the current.  If we believe expand the statement about switch capacity for a 115VAC 6A switch like the C&K mini-switches I previously mentioned, we'd be expecting that mini-switch to handle 46 amps!  Clearly, this is not possible.  The reason for voltage ratings has to do with the insulation, contact material, and the switch travel breaking the contact.

If you buy a 10A switch rated at 115VAC, don't expect it to handle more current at lower voltages.  Also, you would expect to reduce the rating for DC.

When I use AC, I use an MRC Throttlepack AC. I am happy with it.

 Very, very helpful. This makes a lot of sense. Thanks!

Jonathan

You would expect to reduce the VOLTAGE rating for DC due to arcing, but the current rating might remain the same.  Switches are commonly rated for 120VAC and 24 or 28VDC.

The point I was making is there's no way you increase the current rating because the voltage is lower, that just doesn't wash.  However, I've seen the current rating for DC reduced for some relays, and I assume if I looked hard enough, I'd find it for switches.  Normally a switch's contact current rating will be lower for DC then AC current. This is because the AC voltage passes through 'zero' voltage 60 or 50 times a second and helps 'break' the spark gap as the switch contacts open. This doesn't happen in DC so the contacts are subjected to much more heat as the contacts open a DC circuit.

Interesting reading here Dale, I knew I saw this somewhere.  SWITCHES AC VS DC

Regarding to old electro mechanical reversing E units, wouldn't using DC cause the solenoid to magnetize after awhile and start sticking? And I know that AC relays cannot be used on DC as the coild have less turns and also are designed I recall to take advanage of eddy currents and a copper piece to create the magnetism for armature attraction.  DC current does not set up these conditions so the coil burns out after awhile.  So I wonder if the E unit coils also require AC to prevent problems?

Hi rrman, Western Depot train shop in Yuba City, CA sells a kit to put a recifier in the eunit power wire on old locos. The reason is simply to stop the buzz. Some folks hate the buzz. I have one of the kits, but have never installed it. The buzz doesn't bother me.

   Anyway, he told me after a long period of time the eunit will be magnetized & plunger not drop properly. When you notice this, reverse 2 leads of recifier & it will reverse the magnetism. The impression I got is it would take lots of running for a few years to cause issues.

    I have no acutal experiance with that so I don't know how much running it actually takes.

     Very best, Don Johnson

An AC relay can be used without problems on DC if the coil voltage is reduced.   For DC, the impedance of the coil is just the resistance value of the wire without any impedance component due to the inductance of the coil of wire around a metal core.  If you want to determine an appropriate DC voltage, ramp up the voltage slowly until the relay activates, and then add an additional 50%.

The extra ring of copper wire is a "shading ring" that is used to create an auxiliary magnetic pole that is somewhat out of phase with the primary magnetic flux, thus helping to keep the relay closed without buzzing when the applied AC voltage swings through the zero crossings.  If DC is applied, the shading ring does nothing and the entire core is magnetized.

The plunger of an E-unit can become magnetized, but a number of folks have run DC quite successfully.  I would reduce the voltage on the coil by adding a series resistor of the appropriate resistance and wattage.