Large Scale Central

Help with custom control panel

Electronics
#1

Hello all,

Its been a while since Ive been online. I’ve been real busy with different projects (plus my recent promotion at work). But, I’ve started preparing my modules for the ARS show in January. I’ve run into a challenge which I’d like to get some feedback on.

I am trying to build a control panel for my dwarf signal and mainline switch. I have a 12v power supply I can use. The LEDs in the dwarf head are already wired with resistors, so I meed to get the voltage from 12 down to 3 for them. I have read that 12 is okay for the LGB switch motor. Can someone please help me decide weather I need a voltage regulator or if a resistor will do for the signal? Also, if anything else isnt great in my drawing, please let me know!

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#2

I could be wrong, but LEDs need 3V if you don’t use a resistor. The resistor controls the current reaching the LED. I know I wired lights to the track feed using an LED and a resistor.

#3

Right, there is an important concept, LEDs operate on current, not voltage.

A “'current limiting resistor” has it’s value calculated to limit CURRENT to about 10-20 milliamps to the LED… most LEDs that already have the resistor work on 12 volts, but that information would come from the supplier.

So if what you have already have the proper current limiting resistor connected to each LED, then just supply 12 volts to light it.

I’m basically saying the same thing as Pete, but a bit more explanation… There’s lots of web sites that explain the concepts more fully.

#4

Agreeing with Pete and Frank.

Congrats on your promotion, John!

#5

My concern would be the 12 volts for the LGB switch motors. This is “iffy” and sluggish if everything is just perfect. You really want at least 16 volts for reliable operation.

And it just so happens that doorbell transformers come in 16 volts a/c. This can control the turnouts with either the addition of a pair of diodes, or you can put it through a rectifier/capacitor and get ~21 volts.

If you use a relatively small capacitor, this will give the turnouts a really nice “snap” then the voltage will instantly bleed down to what is safe for prolonged contact without burning out the turnout motors.