An extremely basic question about SPST

Model Railroader Layouts and layout building
1

Surprising myself to no small degree, I managed to install a SPST switch on a siding AND get it to work like it’s supposed to (I’m as new as they come to the hobby, having just gotten my first set three days ago). In my head I know it’s a very trivial matter of wiring, but as someone who’s unreasonably afraid of electricity since an unfortunate accident 25 years ago involving an exploring hand inside a turntable that was plugged in, I’m rather proud of myself.

My question is, are all SPST switches created equal? That is, does it matter what kind I use, as long as it’s a SPST switch? I bought two from the local electrical supply store today, and what the labels say is greek to me:

  • 1A 125 V T/6A 125 V L/6A 125 V AC/3A 250V AC

  • 3 Amp 125 VAC, 2 Amp-L, 125VAC

The first one is the one I successfully used on my layout (a starter-set Life-Like N gauge Power-Loc trac with a LL power pack). Could some kind soul decipher the specs for me?

Thank you.

2

Im having trouble with your specs the way you posted them. Those numbers scream HOUSE VOLTAGE. Maybe I drank my coffee wrong I dont know.

3

Well, heck, this will be easier. Here’s a photo of the packages with specs (click to view larger version):

My question is, are there different grades/types of SPST and would some not be recommended for hobby purposes?

4

There is no “Grade” of SPST.

SPST means Single Pole Single Throw and…

DPDT is Double Pole Double throw.

I feel a little better now that you posted that imagery. Your switch should withstand common electrical situations as a normal part of model railroading. House power has much larger values.

5

Fwiw, you can probably get the switches you need for much cheaper at a hobby shop, etc., compared to a hardware, supply, etc. store.

I.e., at my local hardware stores, a switch similar to yours runs for $6-7 dollars…each.

At my lhs, I can get an entire bag of switches for the same price.

Built for hobby specs vs. household specs. is the price difference.

6

Thank you to both of you, thanks for clarifying this. Yes, I did think that $4 per switch was a bit on the expensive side (at Home Depot).

The switch is pretty huge next to the N scale locomotive (almost as tall as a GP20), but I’m still amazed that I got it to work…!

Thanks again.

7

Basically, it means the switch can handle up to 3A at 120V AC.

I’m guessing that if you are switching an inductive load, they rate it for 2A instead.

At 12V, it really isn’t an issue.

You are probably better off using a double pole single throw, as you can kill both rails that way. Otherwise, it will work.

8

Yeah, the hobby switches are smaller in size too. Congrats on the successful wiring, good job !

9

You are right, of course. But one baby step at a time… [:D]

10

Y’know, I looked at this post earlier, and I couldn’t figure out what the “L” meant. Thanks, Betamax. I’ve been around this stuff my whole life, and tonight I learned something new!

Just goes to show ya - it’s never wrong to ask a question here.

11

Yes, all these ratings can definitely be confusing!

What I learned from the “Carling Industries” website (they MAKE switches:

xxxV = DC voltage rating; xxxVAC = AC voltage rating;

L = Tungsten filament lamp load, AC;

T = Equivalent lamp load, DC;

Ind = Inductive load (motor, transformer, etc.

DC Rule of Thumb – if a DC rating is NOT given, the switch should be able to handle the MAXIMUM AC ampere rating, UP TO 30 volts.

/Lone

12

The numbers you are interested in are the first ones (2A 125VAC) this tells you that the switch is capable of passing 2 amps of current at 125 volts AC (alternating current). Since we work with voltage much lower than 125 VAC (house voltage) we realy don’t need to wory to much about the voltage rating of a toggle switch, but the current rating or A (amperage) rating is important. Think of electricity like a garden hose, voltage is the pressure of the water coming out of the hose and amperage is the volume of water. If you need more water (amperage) you need to increase the size of the hose (2 amp contacts to 3 amp), if you want more pressure you just need to increase the pressure, no need to change hose size.

Hope this helps somewhat, I am an X broadcase engineer and some times it is hard for me to put something in layman terms.