How Does This Work?

Model Railroader General Discussion (Model Railroader)
1

How Does This Work?

I bought an 18" turntable fairly cheap at a hobby shop that a customer left for consignment. It was in a cardboard box along with a Railpower 1300 power pack, a rotary switch with a mass of wires attached to terminal strips and about 20 sections of track with this device soldered to each rail. It looks like a small green diode installed in a black box with a resistor across the rails.

I thought it would light if I applied track voltage but it didn’t. The resistor appears to be a 240ohm, +/-5% resister wired to both rails and to one leg of the diode.

I want to hook up the tracks to the turntable. I thought one leg of each track would be attached to the rotary switch and the other to a common ground and the diode device would show a green light if power was applied to the correct track. So far nothing works.

How does this work and what am I doing wrong?

Doc

2

Did you try feeding power both ways across the rail? IE: Pos on left, neg on right, and then switch them?

Did you try doing it on a few different pieces? Maybe the one you tried doesn’t work.

3

looks like a setup for a led to plug in that black section and the resister keeps it from going out

looks just like the lights at the engine house at community college

this is the best thing sence sliced bread

K

4

Thanks for the help guys. The diodes show a green light when track power is supplied in DC and DCC. It was a combination of switching polarity and not making proper contact that prevented them from lighting before.

Now if I can only find out who makes these diodes I can add some to other tracks.

Thanks again, Doc

5

LEDs are diodes themselves. I’m not sure why he has seperate diode in series with the LED unless he was trying to step down the voltage a little.

edit Oh never mind. I misunderstood your original statement. Is it possible that he had the LEDs there to indicate polarity of the track to make sure the turntable and round table track were of the same polarity? (Either both off or both on)

6

That would be my guess. Might have even been inside the engine house/roundhouse - peek in and see what color the LEDs were before advancing the throttle to keep from trying to run the loco out the back wall. Those little black boxes looks sort of like a unit that would be attached to a PC board to supply indicators to some sort of circuit. Sort of like these: http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016+688453+688537+254248&N=1323038+4294943586+4294943030+254248+0&Ns=P_SField&Msb=0&RefType=Header

None of those seem to be exactly as pictured but you can probably get the idea.

–Randy