I sat staring at my turntable mini-panel for a couple hours trying to determine how to wire the dang thing. From the back it looks like this.
The large switch on the right is a MOM and will be used to power the rotation of a pitbashed Atlas turntable. The 4 DTDP switches will be used to kill power to four tracks coming off the the turntable and light LEDs above and below the switch (note two holes above and below each switch) to remind me which tracks are powered. I figure one side of each switch will be the track power and one side will power the LEDs. I'm going to do something similar with staging tracks.
The MOM wiring is very straight forward.
My current plan is to glue a copper fiberglass tie to the left side of the panel which will be divided into 3 sections by filing a groves through the copper. From the center section I will solder 4 green wires that will run to the left center posts of each the 4 DTDP switches.
From the other two sections I will run a single red wire to one the outer lead wires of each LED.
From the switches I will solder resistors from the outer posts to the other side of the LEDs.
IT also makes sense that I go ahead and hook up the track wires and connect them to a terminal strip since laying the turntable tracks will be a ways down the line.
I'm lookiing for suggestions if anyone can think of an easier way to do it.
On another note, I hooked up power to my homemade circuit board that I'm using to power my structure lights.
The power was the AC side of my Bachmann DC power pack. I tested it and instead of being 12VAC like it said on the power pack, it was 17VAC. So I need a new new 12V power supply.
Now I have one the is currently powering 3 UP5s, so there's plenty of current left over. Still, I feel reluctant to share power between LEDs and my LocoNet.
What's your take?
Chip
Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.
Generally power packs are rated at the current being drawn. With no power being drawn, the voltage will always be higher.
Put a meter on the pack and as you had a load you will see the voltage drop until it gets to around twelve volts.
Over the years I have seen this issue mentioned, many times in different forums and magazine articles.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
You really only need DPST toggles, not DPDT. The other side of each toggle will be unused as you have them. The DPDTs you've got will work fine, though.
It's likely that the internal design of the toggle will be such that when the toggle lever is up, the connection will be made to the lower pair of posts, not the upper pair.
An unloaded power supply might show a higher voltage than it will under some load, so it may be just fine to run your LEDs. Put a meter on it once you've got a few LEDs connected.
I would attach a barrier strip or other wire connection device to the panel and do all off-board wiring through that. Once you're under the layout, you'll appreciate the simplicity and convenience of screw terminals or whatever vs. having to solder underneath.
It takes an iron man to play with a toy iron horse.
richg1998Generally power packs for are rated at the current being drawn. With no power being drawn, the voltage will always be higher.
So, how do I dermine if the power will be right for the LEDs?
Most LED's are 20 ma limit. Many use a 1k resistor at 12 vdc, not 12vac. if that is what you are thinking. Just guessing. That allows 9ma of current and plenty of brightness.
MisterBeasleyYou really only need DPST toggles, not DPDT. The other side of each toggle will be unused as you have them. The DPDTs you've got will work fine, though.
I get that I'll only be using half of the MOM. WHen I bought it I thought I was scratchbuilding a TT. However, both the motors I have were just too fast. I was able to get my second hand Atlas working which is omnidirectional instead of bi-directional.
However, while the track needs only half of one side of the switch, powering a LED for both on and off would take whole side of the switch. Unless, I'm totally off base.
The fact that you are probably right about the back of the switch being opposite is throwing me for a loop. I think I have to completely redesign my wiring in regards to the LEDs. Either that or I'll have to live with the switch being up, while the lower light is lit.
SpaceMouseSo, how do I dermine if the power will be right for the LEDs?
Hook up a couple of them wired in series with a 2K resistor, or 2 1K resistors, themselves in series, if you don't have 2K. The combination of a 12 volt supply and a 1 K resistor works as a starting point for most small LEDs we use. The extra resistor will protect the LED in case the power supply really is putting out too high a voltage. You may find yourself tweaking the resistors anyway to get the brightness you want. Once you've got them connected, measure the voltage.
If you're using the AC terminals of the power supply, consider using a bridge rectifier to convert the AC to DC. You will still probably never damage a LED, but they are less likely to fail with DC than the constant polarity reversal of AC.
SpaceMouseHowever, while the track needs only half of one side of the switch, powering a LED for both on and off would take whole side of the switch. Unless, I'm totally off base.
You're right. If you are using lights for both ON and OFF, then you'll need a double-throw toggle.
richg1998Most LED's are 20 ma limit. Many use a 1k resistor at 12 vdc, not 12vac. if that is what you are thinking. Just guessing. That allows 9ma of current and plenty of brightness.
I was under the impression that 12VAC would work, but it would cause an impreceptible flicker--unless you were doing video, then the camera would pick it up.
SpaceMouseI was under the impression that 12VAC would work, but it would cause an impreceptible flicker--unless you were doing video, then the camera would pick it up.
It will work, and the flcker will likely be imperceptible, even to a video camera. My concern is that using DC, the LED is either on or off, while with AC it is turning on and off 60 times a second. It probably won't matter, but that will be slightly more stressful on the circuit and you may only get a century or two before the LEDs start to fail.
SpaceMouse richg1998 Generally power packs for are rated at the current being drawn. With no power being drawn, the voltage will always be higher. So, how do I dermine if the power will be right for the LEDs?
richg1998 Generally power packs for are rated at the current being drawn. With no power being drawn, the voltage will always be higher.
That's why you calculate the resistor for the LED based on a middle valus of current, not the LED's maximum rating. With the nominal 12 volts and a resistor sized to run the LED at the middle of its current capacity, if the voltage goes a couple of volts higher or lower, the LED will still be well within the safe zone and the fact that the voltage isn't precision regulated won't be a problem.
Use 12V DC. AC works, kind of, because the D in LED is Diode, after all. But it also subjects the LED to 12 volts going the wrong way half the time. It's still current limited by the resistor, but unlike a regular silicon diode which is made to stand 50, 100, or more volts trying to go through the wrong way, an LED generally can't handle that. If AC is the only power source, the simple fix is to put a regular diode across the LED terminals in the opposite direction. So when the AC is in one half, the LED lights, in the other half going backwards relative tot he LED, it goes through the regular diode in its forward direction. The LED then only sees the single diode drop backwards, instead of the full 12 volts (.7V or less, vs 12). Usually the resistor value will be a bit lower when using AC as well, since the LED is really only lighting up half the time.
I think you need another switch on that panel - to control the direction of the turntable rotation. Unless you are good with always going around the long way.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The simplest solution would be to go with 12 vdc. Many do that on layouts. A common voltage in decoders also.
The same voltage that operates the TT motor. Our club does that.
rrinker If AC is the only power source, the simple fix is to put a regular diode across the LED terminals in the opposite direction.
Yes, that works too, but I think it's easier to wire in one bridge rectifier to handle all the LEDs than to put diodes on each LED individually.
If it were me, I would just get a 12-volt DC supply online. I've got a bunch of them, and they only cost me about $8 each from China, shipping included. Wire each power supply with a fuse block and fuse, because they do not have breakers and a prolonged short will leave you with an ugly black paperweight. By using several of these, I can put one on each major section of benchwork and use it for all the scenery lighting and electronics.
rrinkerI think you need another switch on that panel - to control the direction of the turntable rotation. Unless you are good with always going around the long way.
I have to admit, I didn't reverse motor direction, but I thought with the geneva drive, the turntable only goes one way. I can go both ways with my DTDP MOM if it does.
If you assume you make an...nevermind.
MisterBeasleyIf it were me, I would just get a 12-volt DC supply online.
Okay, okay. I ordered a 12VDC 2A regulated wall wart for $7. Be here in a week.
SpaceMouseI have to admit, I didn't reverse motor direction, but I thought with the geneva drive, the turntable only goes one way. I can go both ways with my DTDP MOM if it does.
The Atlas Geneva drive does go both ways.
And don't forget the fuse on the output of the power supply.
Yes, it can drive both ways. All the mechanical part of the mechanism does is define the spots where the position is held by allowing it to advance only in set increments. The bits of the mechanism are symmetrical, so it can turn either way. I think the Wikipedia entry on geneva drive has a good animation - I knoow I've seen one somewhere. If you're interested in how it works.
You won't be able to reverse with that pushbutton. It looks like it's DPST, but even if it was DPDT - the only momentary pushbuttons I've every seen in DPDT connected the center to one side when you didn;t press it, and connected the center to the opposite side when you held it down. So it would move continuously one way unless you pressed the button, at which time it would move the other way. You need your basic DPDT toggle wired with the X on the back for a reversing switch, then from there to the pushbutton and to the turntable motor (order of the switches does not matter, power could go to the pushbutton first, then the reversing switch and then the motor).
It looks like you have room below the pushbutton. I'd put it below the button, with the lever moving left and right, and label them clockwise and counterclockwise. Or to use a bigger, more readable font for the lettering - CW and CCW.
SpaceMouseOn another note, I hooked up power to my homemade circuit board that I'm using to power my structure lights.
I want to add lights to buildings, which I have never done. The above looks like it would be used to light multiple LED's but I'm not quite grasping the game plan. Can you explain how you will use it.
Henry
COB Potomac & Northern
Shenandoah Valley
rrinkerou won't be able to reverse with that pushbutton. It looks like it's DPST, but even if it was DPDT - the only momentary pushbuttons I've every seen in DPDT connected the center to one side when you didn;t press it, and connected the center to the opposite side when you held it down. So it would move continuously one way unless you pressed the button, at which time it would move the other way. You need your basic DPDT toggle wired with the X on the back for a reversing switch, then from there to the pushbutton and to the turntable motor (order of the switches does not matter, power could go to the pushbutton first, then the reversing switch and then the motor).
I'm not sure where you are seeing a push button. The large DPDT is a MOM in both directions. When you release it, it goes to center.
It occurs to me that you can't see the front of the switch.
BigDaddy I want to add lights to buildings, which I have never done. The above looks like it would be used to light multiple LED's but I'm not quite grasping the game plan. Can you explain how you will use it.
It you look at a larger image you will see that there are two rows of copper strips joined by red or green wires.
There is a third row of strips and between the third row of strips without wires joining them. If you look closely at the row of strips without wires joining them you will see a cut through the copper between each of the resistors. There is also a hole next to each resistor. The two wires coming from each individual LED will come through that hole. One will attach to the (red) resistor side and one will attach to the common green side.
Each LED will have it's own resistor and it can be wired without having to crawl under the layout. Here's what it looks like mounted on the side of the benchwork.
The town of Rock Ridge is above that board. As it stands I can wire 30 LEDs from it. If that is not enough, there's room for 18 more. It will eventually be covered by facia.
MisterBeasleyAnd don't forget the fuse on the output of the power supply.
What kind of fuse to you recommend? The Wall Wart coming is 12VDC 2A.
SpaceMouseWhat kind of fuse to you recommend? The Wall Wart coming is 12VDC 2A.
1 1/2 amp fuse. Don't worry about the voltage rating on the fuse. That's a maximum value and does not really matter here. You want to make sure you're protected if the current draw gets close to the current limit of the supply. Stay a bit under the supply's rating to be safe.
Oh, OK. For soome reason I thought it was a pushbutton.
Second the fuse idea. Wall Warts usually are already fused - but it's a one-time thing, not replaceable. Using a 1 1/2 amp fuse on a 2 amp wall wart keeps you honest on the current draw and a mistake means a 50 cent fuse and not a new $5 wall wart.
Thanks Chip. I did not see that the circuit board was scored. I am looking for a solution that is also unpluggable, for a future move, but I can incorporate your idea.
SpaceMouse rrinker ou won't be able to reverse with that pushbutton. It looks like it's DPST, but even if it was DPDT - the only momentary pushbuttons I've every seen in DPDT connected the center to one side when you didn;t press it, and connected the center to the opposite side when you held it down. So it would move continuously one way unless you pressed the button, at which time it would move the other way. You need your basic DPDT toggle wired with the X on the back for a reversing switch, then from there to the pushbutton and to the turntable motor (order of the switches does not matter, power could go to the pushbutton first, then the reversing switch and then the motor). I'm not sure where you are seeing a push button. The large DPDT is a MOM in both directions. When you release it, it goes to center. It occurs to me that you can't see the front of the switch.
rrinker ou won't be able to reverse with that pushbutton. It looks like it's DPST, but even if it was DPDT - the only momentary pushbuttons I've every seen in DPDT connected the center to one side when you didn;t press it, and connected the center to the opposite side when you held it down. So it would move continuously one way unless you pressed the button, at which time it would move the other way. You need your basic DPDT toggle wired with the X on the back for a reversing switch, then from there to the pushbutton and to the turntable motor (order of the switches does not matter, power could go to the pushbutton first, then the reversing switch and then the motor).
Speaking of "eloquence"...
May I suggest LED panel sleeves or bezels for holding your LEDs in the panel?
https://tinyurl.com/y98n6vpt
There are several varieties available. The chrome ones look very nice and direct the light forward so it reduces glare. **
https://tinyurl.com/y94mbv3j
I often use the plastic ones. There are times when I have to replace a defective LED and these make it easy to snap a new LED in place — and, they look Eloquent
IMG_0168 by Edmund, on Flickr
**Both those Ebay listings are only for example. I bought from other suppliers.
[Edit] and P.S. Are you passing the LED leads, from the front, through those two holes you drilled in the panel? That seems like a lot of work. Even before I was using the bezels I pushed the LED in through one hole, from the back.
Is the panel metal? That would be asking for trouble...
Good Luck, Ed
RR_MelCould I suggest Perf Board for the resistors and other small parts.
I found one of those just today and I do not remember buying, probably 30 years ago. My Harbor Freight meter reads 1.988 on all modes unless it reads 19.88 or 198.8. Are any of the rows or columns in continuity?
Would a solderless bread board be more useful?
BigDaddy RR_Mel Could I suggest Perf Board for the resistors and other small parts. I found one of those just today and I do not remember buying, probably 30 years ago. My Harbor Freight meter reads 1.988 on all modes unless it reads 19.88 or 198.8. Are any of the rows or columns in continuity? Would a solderless bread board be more useful?
RR_Mel Could I suggest Perf Board for the resistors and other small parts.
RR_MelThe perf board is a fiber board with holes that are through plated for soldering.
Okay, I got the perf board and the bezels for the LEDs.
Given my switch plate--
--actually I've decided to start over-- how would you incorporate the perf board. There doesn't seem to be enough room to mount the board in a porductive way. I suppose I could cut it and mount it at a 90 degree angle to the switch plate.
Suggestions?
SpaceMouse RR_Mel The perf board is a fiber board with holes that are through plated for soldering. Okay, I got the perf board and the bezels for the LEDs. Given my switch plate-- --actually I've decided to start over-- how would you incorporate the perf board. There doesn't seem to be enough room to mount the board in a porductive way. I suppose I could cut it and mount it at a 90 degree angle to the switch plate. Suggestions?
RR_Mel The perf board is a fiber board with holes that are through plated for soldering.