I am presently building a new control panel for my railroad. I’m using tempered hardboard for the board with the track diagram on it. I power my layout with DC and all of my turnouts are manually operated. I’m installing toggles for my cab selectors for each block. I want to use 3mm LED lights to indicate which cab is powered in each particular block using two pole- DPDT on-off-on switches, one pole at each terminal for track power, one for the lights. The LED lights will fit holes that are big enough for the light to show through the board from the back side and small enough for the “lip” of the LED to seat onto.
My question is: What is the best adhesive to use to attach these LED’s to the back side of the board? I was thinking of using Aleene’s Tacky Glue. I think CA glue will simply get absorbed by the porous hardboard and not ahdere to the plastic LED. Any thoughts?
Seems that the tacky glue would be a good choice, or maybe canopy cement?
My control panel is also tempered hardboard and I used the cheap plastic bezels to mount 3mm LEDs for turnout indication. The LEDs pop right into the bezel and can be popped back out if need be.
I did something like that once. I didn’t use glue at all, there is enough friction between the LED and the hole to keep the LED in place. Besides, occasionally you have to change LED’s. Have you given any thought to where and how you are going to mount the LED current limiting resistors?
What you really want to do is not glue them in. If you are using 3mm or 5 mm LED’s, just buy a package of LED holders. The snap into holes drilled into your 1/8" Masonite, and the LED’s snap in from behind. A nice neat solution. You can order them from most on-line electronics firms, or if you have a local Radio Shack, they may stock them(mine still does).
I personally just rely on the press fit of the 3 mm led in 1/8 inch holes drilled through my masonite facia. I attach the limiting resistor directly to one of the led leads and use solid 22 gauge copper wire to hook up the led in my circuit. The stiffness of the solid wire ensures the leds do not inadventantly pop out. I used this mounting method to indicate throw of turnouts and have had no issues in the 15 years since they’ve been installed. As mentioned, it is much easier to replace any dead led if they are not glued in place.
But if you must, a smal dab of any white glue will do the trick. [:D]
I think the holder or bezel idea is a good one. However, I already drilled the holes for the LED’s and they’re right next to the toggle switches, allowing a small amount of room for a bigger hole if it needs to be enlarged for the holder. A significantly larger hole may not work, as it may interfere with the terminal block on the toggle.
Also, on resistors, do I have to use a resistor for each LED? Can I use a resistor for each pair of lights at a toggle, since only one of the two will be lit at a time? I was going to use a single resistor for the whole circuit - - guess I can’t do that!. BTW, I’m using a 5 volt “wall wart” DC transformer, was thinking of using 120 ohm resistors. Will that work?
These are the smaller LED, but the idea is the same. LION does glue the LEDs of him with silicone caulk from the back. That holds them in place, but if I want to change them they will sill pull (push?) right out.
Here is wiring of said board: The array to the right is were the cables come in from the layout (60 conductors), and where I connect the LEDs to their sources.
I use 3 mm LEDs on my control panel for all kinds of indicators. I buy the chrome bezel type holder, they come with a nylon insert that snaps in the rear to hold the LEDs in place. I also use miniature toggle switches with colored sleeves that slip over the lever to separate blocks and turnouts for the younger operators.
I went with 4PDT on-off-on toggles for my block control where I wanted LED indication for the position of the switch. For my Atlas and Peco switch machines (solenoid) I use DIP latching relays for LED indication. For Tortoise machines I use their contacts for LED indication.
For LED power I use a 560 ¼ watt (about 7ma) resistor from a 5 volt regulator off my 12 volt accessory power supply. I don’t like bright status indicator LEDs on my control panel. I do run Warning LEDs at 15ma to make them obvious.
A lot of people recommend a resistor for each LED. However if you are using a DPDT switch and connecting them the the output of the switch (one wired each way in parallel) then 1 resistor will do.
red and green leds will start to light about 1.2 to 1.7 Volts forward. With a 5 Volt source, that 3.8 Volts (5-1.2) / 120 = 31 ma. That’s a lot of current. I would at the very least shoot for no lower then a 240 ohm resistor if your LED can handle a 15ma supply current. (And this will be bright)
As I am electronically iliterate, I’m not sure whether this is in parallel or series, but I can tell you how I plan to have it hooked up (unless this will not work, but I tried it and it seems to work).
The power source will go to two different terminal strips, one that will feed the (+) terminal on each LED and one that will feed to the “common” (or middle position) on each toggle. The toggle will make contact with the (-) terminal of the LED. As for the LED’s and the ma rating, I don’t know. I think they’re rated at about 1.5 volts, however.
I also wonder why this happens: when I tested this wiring system out, when I put the toggle in one contact postion, it activates the opposite position. for example, when I put the toggle in the “up” position, it activates the “down” contact and vice versa. When I wire the contacts the opposite of the toggle position (wire the “down” contact for the “up” position on the toggle) it will then activate according to the up or down position on the toggle.What am I doing wrong?
I don’t know about anyone else but I have a hard time talking about circuits without pictures. How about starting out with a basic picture of a DPDT switch with numbered terminals and then connect the dots.
LIONS never put their LEDs in series with a motor or relay. By putting them in parallel with the motor (as shown below) I can put them on the layout, on the model board, and on the control panel.
Here there are three signal masts and one tortoise all controlled with a single wire (and the ground bus).
I don’t know about anyone else but I have a hard time talking about circuits without pictures. How about starting out with a basic picture of a DPDT switch with numbered terminals and then connect the dots.
You don’t need both sides of the switch to operate the LEDs. A SPDT switch would work fine. You can tie both + legs of the LEDs together on one resistor (common), you only need to switch one leg (-). Tie a – led to each switch terminal (2 & 6). Your LEDs will draw 20ma with a 120Ω resistor from your 5.6 volt supply. 20ma is max current on most LEDs so they will be at max brightness.
