Hello
I have installed LED SPDT switches (3 pin) for block controllers but when the switch is turned on the LED only lighs up then the train direction is set to reverse. I have tried changing the polarity at the power pack but still get the same results. LED only lights in reverse.
Do I need a jumper wire between two of the three pins or should I be looking for another type of switch.
Any suggestions or thoughts.
Thanks in advance. Alez
Are you using the SPDT to manually control the LEDs? Or, is there some connection with the track as well? A diagram would really help.
DC or DCC? I'm guessing DC based on what you've told us, but just to make sure.
LEDs only work with one polarity, and do nothing if the polarity is reversed. It sounds like this may be your problem, but without a wiring diagram it's hard to say for sure.
It takes an iron man to play with a toy iron horse.
Are you using DC cab control and want an indicator to show which cab is selected?
Common rail to track not shown.
DPDT_2 by Edmund, on Flickr
[I forgot to draw in the little arrows to show "Light Emitting" part of the diode]
You would need double-pole-double throw center off switches. One side would feed cab A or B to the gapped rail (block) the other side would illuminate one or the other LED. If you had a 12 volt DC supply for the LEDs (a wall-wart would do) then R would be about 1K Ω.
Good Luck, Ed
Im using the SPST Switch for manual control of the isolated blocks.
My Setup is DC
The switch lets me run the train in forward and reverse but the LED light only comes on in reverse.
Alez
LEDs only light when electricity flows in one direction (in your case, apparently reverse).
Either use two LEDS in reverse-parallel with each other -- Anode of one to cathode of other; or use an incandescent lamp; or a bridge rectifier so the LED always gets the correct polarity.
-Dan
Builder of Bowser steam! Railimages Site
Sounds like a SPDT switch with an LED built in. Such a thing is almost certainly not built to handle the polarity on the common leg changing, and also likely only works over a limited volatge range.
To indicate which way the toggle is thrown, you need somethign liek ED's circuit. A DPDT switch, with one pole switching the track power and the other pole controlling which LED lights. Since the LED power supply is independent of the track power supply, direction on the power pack won't make any difference.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Easy test:
Assuming the SPDT, resistor and LEDs are connected to the power pack or track power and nothing else, disconnect from that source and instead connect it in the same way to a 9 volt battery. When you get the polarity right, the LEDs should behave regardless of the direction of train travel.
Any chance a Bi-color red/green LED would work, as the polarity changes the color changes?
Would a 4 pin LED DPDT switch work?
Alez Would a 4 pin LED DPDT switch work? Alez
Probably not. Get a simple bridge rectifier. Connect its AC side to the input power, and then the DC side where the power goes into your circuit. If it doesn't work, reverse the DC leads.
Hi, Alez
It would really help if you could let us know what type of switch you are using. Is the LED built into the switch? Three pin or four pin doesn't really help. There are single pole single throw, double throw, double throw-center off. then two pole, three pole and even four pole for reversing three phase motors.
In model railroad use, the DPDT is pretty common and that is usually the type of switch I use for reversing track polarity or selecting the "throw" of a stall-motor switch machine. By having a two-pole switch you don't have to use both poles so if you want a simple on-off switch it will work for this. For block control you commonly use a SPDT-center off switch so you can kill power to a track. However, using a double pole in this situation gives you an extra set of contacts that could drive an LED indicator or even a trackside signal if you choose.
Then, tell us what you want the LED to show. It sounds like you want to indicate weather the block is live (switch closed) or dead (switch open).
Are these switches used as cab selector switches, as in DC block control where you have two or more "cabs" or throttles controlling blocks isolated with insulated rail joiners on one rail (common-rail cab control)?
You can not expect an LED to pass the current required to power your track. That will make firecrackers out of them. IF you are selecting between two cabs and you want an LED to indicate which cab is in control of the block you would have to use a circuit like I crudely sketched above.
Help us fill in the blanks.
A model number or part number, and/or manufacturer, or even a link if you got them on eBay or something - woudl definitely help. Although I think if the purpose is to light an LED to indicate that you have tuened the power on to a specific track, then something where the LED is completely independent is absolutely required here, otherwise the toggle might be on, but if the throttle is at off, the LED won;t light.