Plan on using 18v3.3adc supply for Kadee 309 electromagnetic uncplr (It was closest I could find to Kadees spec of 3a/16-18v. Trying to find push button or rocker switch. Getting different opinions as to what is min. rating I need. Per Kadee a 3a switch is sufficient(probably because its the one they sell). Per Mouser as long as amperage rating is above 3.3a it doesn't matter if ac or dc volts. At Del City (where I found a style I like), some of their switches give both ac and dc specs, others just ac. I was told if the spec sheet doesn't list a dc rating then it is for ac use only. Kind of electrically challenged but if a switch is rated at 16a/125ac shouldn't it be able to handle 3.3a/18vdc? Would prefer to use either rocker or push buttons that have a finished housing, hence my dilema. There doesnt seem to be a large selection of rocker/push buttons with the current specs I need and unfortunately, the style I really like (which oddly enough only has a dc rating) is only rated at 3a at 12vdc. After reading past posts I hope I'm not going to regret installing the 309's. Am I correct that the switch needs to be rated at a minimum of what the power supply is?
Of those of you out there that use the 309 what power source seems to work?
Any help/suggestions would be greatly appreciated
Thanks in advance
Joe K
Kadee lists their part number 166, Amseco® XR-1650LED Transformer on their web site, though it's tough to find. I took that model number and found it someplace like All Electronics for much less.
Yes, ideally your pushbuttons should support the full rating of the power supply. They should also be spring-loaded momentary contact switches or buttons. If a button exceeds both voltage and current rating of the supply, that's even better.
I couldn't find anything I liked with that kind of rating, and I was in a hurry, so I installed something smaller and very cheap, figuring that if it failed I would have learned my lesson, but it wouldn't have been a costly one. So far, so good. In general, the problem with pushbuttons isn't steady load, but arcing which can occur when you drop a very big load on all of a sudden. Electromagnets don't do that, because the field takes some time to build up. So far, so good with my under-rated pushbottons, but I wouldn't recommend it.
It takes an iron man to play with a toy iron horse.
Thanks. Any truth to the info that if there's only an ac rating that the switch can't be used with dc. Per Kadee their 166 is ac and although the 309 will work on ac they still recommend dc and that if I use their 166 I should use a bridge rectifier to convert it to dc. They told me that the 166 is ac because they use it with other products. Not knowing much about electronics I was following their advice and found an 18v 3.3adc at Mouser which led me to trying to find a corresponding momentary switch to match/exceed the power source.
Kadee does recommend using DC for the magnet. I bought mine a couple of years ago, but they came with a very hefty bridge rectifiier in the package, so I'm using it to convert the AC from the supply before it goes to the magnet.
Buy some decent wire for this, by the way. I'm using 20-gauge, and 18 would probably be even better.
There's no reason a switch can't be used for both AC and DC. Having said that, I'm going to contradict myself somewhat.
You will notice that if the give both AC and DC specs for a switch, the DC spec is always lower than the AC spec. By that I mean the amount of current that the switch can tolerate. The reason is that AC goes through a zero voltage point twice every cycle (120 times a second in North America). When a switch is opened under load, there is an arc developed between the contacts as they start to open up. Because of the swings through zero with AC, that arc is quickly extinguished. DC has a steady voltage so the arc will last longer. As long as you don't exceed the switch's DC current rating you're okay. If only the AC rating is specified, my best guess would be about 25% of that for DC. Another factor is the internal construction of a switch made for DC will be sturdier, if you will, to handle the heavier arcing. Finally, a switch rated for 120 VAC will have more insulation to protect the user than a switch rated for just 12 VDC.
I'll also repeat what MisterBeasley said about wire. #18 wire would be best for the high currents involved with uncoupling magnets.
I hope this helped you and didn't confuse you further.
..... Bob
Beam me up, Scotty, there's no intelligent life down here. (Captain Kirk)
I reject your reality and substitute my own. (Adam Savage)
Resistance is not futile--it is voltage divided by current.
Thanks for the info. If I'm understanding you correctly, a switch with an AC rating of 16A/125VAC should be able to handle 3.3A/18VDC(25%of16=4?). I'm trying to find a power supply with a slighlty lower rating (3A/16VDC?). Kadee wasn't much help. All they would offer is getting their #166 and finding a bridge rectifier. They also said that the higher the amps and volts the stonger the magnetic force and if I use a power source higher than their recommended 16-18V/3A I would have to experiment and keep checking the heat build up when in use to keep from melting the plastic and damaging the coils and compare that to the amount of magnetic force created (if too strong it will pull the couplers down instead of to the side) Unfortunately I don't have a supply of various power supplies or the elctrical knowledge and supplies to do a bunch of field testing. As you can tell I don't have much of a clue as to what is best. Kind of makes me wish I was 50 years younger and still had my old Lionel 027 set. Never had a problem with their uncoupler.
In terms of the wire size, before installing the 309's I soldered on a 6" length of 20awg. Would you recommend going from the 16/18 awg directly to the coil wire or would it be ok to leave a short length of the 20awg?
Thanks again for any help/comments/suggestion
Joe K.
First off, any momentary switch that's rated for 120volts/3amps will work just fine whether it's AC or DC, you're only running 18volts through it and the amperage is the same (3a).
Secondly, replace the 20g wire completely with 18g.
Jay
C-415 Build: https://imageshack.com/a/tShC/1
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LION tried an electric Kadee only once and it is long gone.
LION (on his previous layouts) used a "Cutting Key" for parting trains over the magnet. Locomotives were so smooth that sometimes a car would not uncouple over the magnet. Well I was running in just one direction, and not backing up over the magnet.
The cutting key was simply a reversing switch built on a dpdt momentary push button. The train would pass over the magnet and I would hit the cutting key. The "jerk" movement was not even visible to the person watching the operation, but it was enough to uncouple the car.
On my present layout, the Route of the Broadway LION, there are no uncouplers at all. All cars are joined with a draw bar, and nothing gets uncoupled except on the bench.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
slammer406 Thanks for the info. If I'm understanding you correctly, a switch with an AC rating of 16A/125VAC should be able to handle 3.3A/18VDC(25%of16=4?). I'm trying to find a power supply with a slighlty lower rating (3A/16VDC?). Kadee wasn't much help. All they would offer is getting their #166 and finding a bridge rectifier. They also said that the higher the amps and volts the stonger the magnetic force and if I use a power source higher than their recommended 16-18V/3A I would have to experiment and keep checking the heat build up when in use to keep from melting the plastic and damaging the coils and compare that to the amount of magnetic force created (if too strong it will pull the couplers down instead of to the side) Unfortunately I don't have a supply of various power supplies or the elctrical knowledge and supplies to do a bunch of field testing. As you can tell I don't have much of a clue as to what is best. Kind of makes me wish I was 50 years younger and still had my old Lionel 027 set. Never had a problem with their uncoupler. In terms of the wire size, before installing the 309's I soldered on a 6" length of 20awg. Would you recommend going from the 16/18 awg directly to the coil wire or would it be ok to leave a short length of the 20awg? Thanks again for any help/comments/suggestion Joe K.
That sounds like a light switch for the house! It would be able to handle the current of an uncoupler.
Pay heed to Kadee's advice. Their uncoupling coils are built for 16-18 volts and would draw a certain amount of current at that voltage. Increasing the voltage will also increase the current through the coil and increase the heat they produce. If you go too high with the voltage, a meltdown in quite possible. Stick to something in the 16-18 volt range. This is just a guess on my part but possibly the reason those coils (and some incandescent bulbs) are rated for 16 volts is that the accessory output of many DC power packs is 16 volts so they were designed to operate from those.
Yes, go #18 right to the coil.
I just had a thought. Maybe you could find suitable switches or pushbuttons at an automotive supply store. They are designed for 12 volts--actually 13.6 volts (and should handle 16 volts with no problem) and many are designed for high DC currents. Just make sure that whatever kind of switch or pushbutton you get is a momentary type.