LEDs for Dummies

Note Stans alternative as well, I have used the LM317 as a constant current device as well, just adds a resistor to the mix.

The pre-wired strips are most decidedly not just for command users, conventional users can run them just fine.  A simple voltage doubler is all it takes to light them from very low track voltages.

The reason I like the strips is they spread the light more evenly than a much smaller number of LED's.  I'm not sure why you don't like the voltage doubler, you rarely are going to see that kind of voltage, as conventional running typically isn't full throttle on the transformer. Since the input/output voltage differential of the LM317 is 40 volts, and the drop across it in constant current mode is not that significant, nothing here will be close to it's voltage limits.  For insurance, I'd probably recommend 50V capacitors.  Also, since we're talking 20-30 milliamps to drive the LED's, the power dissipation isn't all that great, even at full voltage.  You can use the LM317T in the TO220 package, that will handle plenty of power for the task without a heatsink, and it won't even break a sweat.

What bridge rectifier voltage doubler are you speaking of?  If you double the voltage anyway, doesn't that render your high voltage argument somewhat moot?

Dale, I don't know anyone that wants their cars lit to the maximum that the strips will do, that would, quite frankly, look ridiculous!  At 20ma, my 18" cars are pretty bright, probably way brighter than would be prototypical.  I have a set that I've actually added some shunt resistors to bring down the intensity a bit, it's the easy way to regulate the current to the LED strip.  I can't imagine anyone running those lights anywhere close to the maximum current for lighting passenger cars.

You're creating a "problem" of power dissipation where none exists.  You're taking an extreme situation of full throttle on the track, and full intensity on the LED's, and inventing a scenario where you'd have excessive power dissipation.

If you're really concerned about the voltage doubler and the power dissipation, I have the solution, here's a 96% efficient switching step-down regulator that will do the trick with minimal power dissipation, even at full intensity of the strips, it's $2 on eBay.  I've used a similar product in buildings with strings of LED's to regulate the lighting, this little module doesn't even get warm.

I love it when the propeller heads go toe to toe! I learn so much. Keep it up guys!

The CL2 in the TO-92 package is rated at .6W at 25C ambient.  With your figure of 36 volts and 20ma, the power dissipation of the CL2 is .52W.  So, even at the extremes of your example, we're doing just fine on the power dissipation.  The strips are dropping about 10.5V at that current, and I figured on 26 volts at 20ma across the CL2.

If you like the sunlight look, that's fine, but I suspect a majority of folks here are not interested in having blinding lights in their passenger cars.  I've assisted quite a few people in this conversion, and the only adjustments I've had to make in the intensity of the lighting is to decrease it.  It's amazing how little current you have to provide to the strips to get a lot of light.

You have your way, and I have mine.  That's what makes the world go around.

To take this conversation back to the beginning: First let me  say that both Dale and John each have much more knowledge regarding these things than i ever hope to have, and both their approaches seem to have validity to the extent i understand them.

However, i have been using the variable regulator (DC to DC) shown in the first post combined with the small full wave bridge rectifier i mentioned shortly after the first post to light both cars and buildings with LED's. By simply turning the small brass set screw i've been able to vary the brightness in each car (and building) to the level i want. The only disadvantages i'm aware of were pointed out by John in an earlier conversation are cost (his were even cheaper!) and size (the DC - DC regulators take a little more room - i hide them in the rest room ends of a passenger car). I like the ability to vary the brightness of the LED's by simply turning a set screw.

So are there any technical reasons for not using this approach? It's been working fine for me for over a year now.

jackson

No reason at all Jackson, there's lots of ways to skin this cat.  If you end up with the desired result at a reasonable price, you're home free.

Do you happen to use TMCC?  These modules use high-speed switching signals to perform the power conversion.  Some, such as those with the 2596 device, switch at about 150 kHz.  The 3rd harmonic of this is 450 kHz which is very close to the TMCC command frequency of 455 kHz; normal production tolerances would have some modules putting the harmonic smack on top of the TMCC signal.

When these modules first came out I remember observing this switching noise reflected onto the input (i.e., dumped onto the track voltage) and commenting on this potential interference.  I don't have TMCC to see if there's even a problem but have wondered about it since that time. 

The solution (to repeat, I don't know if it's even a problem) might be a 5 cent choke as is done for DCS...or perhaps just choose a module that uses a device that switches at a compatible non-interfering frequency.

But what about all those chopped-sinewave supplies out there?  Even at lower throttle voltage, the peak voltage appears on the track.  For the voltage doubler configuration you're showing, doesn't the "input" capacitor transfer the peak voltage to the "output" capacitor?  I suppose with some experimentation, you could fiddle with components to limit doubler output voltage.

The "for dummies" train has left the station.  That said, if anyone is interested in conventional mode alternative, perhaps we need a new thread.  IMO the simplicity and intent of the original post is getting side-tracked?

Stan2004,

Yes i use TMCC exclusively - have been for about 10+ years and have had no problems, and have been using these regulators for over a year. What kind of problems should i allegedly be having?

jackson.

1. Dale, note that if I wanted 40ma, I just have to parallel another CL2 with the first one, it's dirt simple to expand the current if I needed it.  The CL2 is actually a pretty nice little part.

2. I've actually run with the voltage doubler on an LED strip, and there is no discernible change in the LED intensity from the open bell as soon as the 1033 I used to test was cracked from zero.

3. You want a pot to vary the intensity?  Connect a 1K pot across the output and you have your dimmer.  You can also use a resistor shunt the same way to bleed off a little of the current.

You're making the mistake of not considering the peak, when you rectify the 6 volts DC, you actually get around 8 volts out of a single diode and cap, and I get about 14 volts out of the voltage doubler, that's with the 20ma load.

The configuration I posted works fine for conventional, let's leave it at that.  I'm not sure why you're so hard over on proving it's not going to be satisfactory.   Honest, I'm not going to try to force you to use my method.

I'm taking Stan's advice, and leaving this alone.  You can have the last word.

You'd see less reliable or missed commands...and if you removed the passenger cars using the modules, everything would be magically return to normal.  But since you are not having any problems, this was a false alarm.

Given these modules are now about $1, and you have a toilet (!) to put it in, I think it's a great idea.  As GRJ points out, and my experience concurs, these 12V LED strips are typically driven at 10 to 11V to get a suitable brightness...but to each his own.  And if running TMCC/DCS with full track voltage, these modules are more efficient and use less power than the CL2N3, LM317LZ, or plain resistor methods.  The power levels may be small, but a Watt is a Watt and a penny saved is a penny earned.  By regulating voltage, these modules also make it easier to add marker lights (LEDs), vestibule lights (LEDs), which if there's any interest should be explored in a separate thread.  Again, apologies to Tmack for any hijacking violations...

Stan2004 - All the discussion is good even if it migrated to passenger car lighting.  Everyone is trying to accomplish the same with both scenery and passenger cars, just getting a better understanding is good for all as long the giants remember there are a bunch of people here that need the information on a more basic level. 

Jackson,

Do you happen to have the eBay item number on these? I would like to give these a try in addition to other couple of methods to see which fits my time and talents best.

Thanks,

Jason

I would also like a list of part #s  for doing this . I have ordered most parts through the mail already but I don't know if I need other parts. So if any of you can put up a complete listing of parts  for lighting cars, or other buildings, that would be great.

A complete listing on parts needed.? 

Jason,

Try these numbers:

 Regulator http://www.ebay.com/itm/130984321712?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Rectifier

http://www.ebay.com/itm/50pcs-2W10-2A-1000V-Bridge-Rectifier-/140804400401?pt=LH_DefaultDomain_0&hash=item20c898a511

LEDs

http://www.ebay.com/itm/5M-300-LED-3528-Warm-White-Waterproof-Light-Strip-12V-/160590634760?pt=Kids_Teens_Lamps_Lighting&hash=item2563f29f08

Just Google Warm white LED strips Buy it Now and you’ll get more choices. As far as the rectifier goes 1000 volts is overkill, but the size and configuration was important to me. As to the voltage regulators, if you're looking for quantity just Google it and look for a similar regulator priced in quantity or message the vendor i gave you and ask for quantity pricing. Have fun.

jackson

Many thanks -- order placed for the regulators, ordered all the other bits last week so within a few weeks this project should be well underway.

I've been reading the LED threads for about a year, this one was the first to actually explain it clearly enough to move me to buy the parts and make the attempt.

Thanks to everyone who replied.

I believe these are the same LED's as modeltrainsparts posted above from same supplier only not waterproof for a little less $$

LED's - non waterproof

I have used this same set from same supplier with good results. I'm also saving the links for the products mentioned above.  Thanks to all for posting!

stan2004,

Looks like a good idea there. Where did you get the small boards to mount the diodes & terminals on? Those look like they would be nice to have also. Only thing these need now is a digital readout so you don't have to get a meter to set them, no increase n price of course...

I have a pile of the proto boards with the .1" holes, I use them for all sorts of little circuits.

I have a bunch of LM7805c Rectifiers would they work?

Mike, you can use the 7805 rectifiers with a small series resistor for individual LED's.  A 100 ohm resistor is right for white LED's, and I'd use a 170 or 220 for colored LED's.  For the 12V strips, the 5V regulator is problematic.  There are configurations with a couple of resistors to make them variable voltage, but you'd be better served by just getting the right parts.

With regard to project boxes, one consideration when choosing these DC-DC modules is mounting holes.  Not all of them have them.  What I often do for mounting is use "scrap" acrylic sheet and mount the DC-DC module and screw-terminal board on nylon washers (the bottom of the boards are not flush). When I additonally need to protect the top-side from falling objects or the like, I'll use #4 nylon posts to mount a thin acrylic sheet.  So it's only a 2-sided "box" but works for me.

Oh, and it goes without saying that you can actually buy Harbor Freight "FREE" coupons on eBay (search "Free Harbor Freight coupon"). 

Looks like a nice mounting method there. I need to get some of that acrylic to have on hand for this type of stuff.

Also glad you pointed out the 'free' harbor freight coupons, had no idea those were available on ebay?  I really don't look around on ebay enough. The things you can learn here!

I have been following this tread with great interest and have learned much. Would it be OK not to mount the circuit for leds on a circuit

board, but instead, mount them directly on the MTH passenger car frame in the different compartments?

Thanks.Ron

Thank you Dale H and gunrunnerjohn for your response

Ron

John

Got all my parts for the conversion. On the CL2 is one lead not used. Looks like the center one in your picture isn't used. thanks...

Yep, I cut the center lead off right at the part as it's useless.  The reason it's there is it's cheaper for them to use the same leadframe as other 3-pin TO-92 parts.  In a former life, I used to build the electronics and servos for molding parts like this.

Michael,

I am not sure if this will cause a stir or not,  but I use old Cat5 twisted pair.  I power and old Telephone punchdown block.  I split it in half so I can run approx 45 LEDs per circuit. 

If you're powering LED's unless you're powering a LOT of them, any wire size you can find is probably sufficient.  I wire passenger car updates with #30 wire-wrap wire, very fine and easy to hide.

The Miller Engineering ones would be fine (the ones like MTH has) and probably the easiest.  These are cheaper, but you would have to use jumpers for the power and commons.  Eurostyle terminal strip  These are from All Electronics, but I think Radio Shack has them also (they used to, but last time I was there they were closing some of them out, so not certain on that). They might be a little large for the cat5 though, may have to fold the ends over a time or two to get it to grab?

You can use any terminal you want, I just happened to have one of these laying around.  This is how I got two circuits out of one.  As for CAT5,  CAT5e and CAT6 is what you want these days for your home network, so ask around especially any computer techs to see if they have any old CAT5 laying around that they will give to you.

Don't mean to get off topic here, but how do you guys make these great drawings of this stuff? I have seen many really nice drawings and schematics here on the forum, and would maybe like to make some myself someday.

This was done on my Mac with a program called Pixelmator.  It is $29.00 and is very powerful.  I do not own Photoshop any more, because of the expense and everything I can do on Photoshop I can do on Pixelmator.  I took a Photo of the punchdown block and then used the software to draw the lines in different color. 

Thanks to TMack and others for the great thread.

Regarding lighting passenger cars with conventional control, using the DC-DC converter with a rectifier what is the minimum track voltage to light the LED strips? 

Thanks, Don