New Interior Light design.

[foxhsu]

Just find this info. Looks like it has better effect than the factory design.
http://modeltrainset.blog130.fc2.com/blog-entry-13.html

[Bernard]

The step-by-step video makes it look fairly easy to do. Nice find!

[Webskipper]

I like the fiber optic type set up but, I don't want it any brighter than the Kato FL11 because the seats are empty. It's just right with the Kato kit.

[stevenh]

Supposedly these CRDs are a 'new technology' from Japan. The E-153 he uses can take up to 25v and will limit that to 15mA.

You can buy them from Rakuten: http://en.item.rakuten.com/rfad/e153/
And here's the datasheet: http://www.atcsemitec.co.uk/pdfdocs/SemitecCRDs.pdf

This means that the input voltage can fluctuate and the current output will remain constant as long as it is above the voltage rating of the LED. Really a very neat idea!

[CaptOblivious]

Supposedly these CRDs are a 'new technology' from Japan. The E-153 he uses can take up to 25v and will limit that to 15mA.

You can buy them from Rakuten: http://en.item.rakuten.com/rfad/e153/
And here's the datasheet: http://www.atcsemitec.co.uk/pdfdocs/SemitecCRDs.pdf

This means that the input voltage can fluctuate and the current output will remain constant as long as it is above the voltage rating of the LED. Really a very neat idea!

CRDs are available in the US, but are hard to find, because they aren't often used. Finding ones with current ratings of 15mA is quite hard, though!

[Tenorikuma]

I just bought a bunch of CL2N3-G current regulators. It's a single component that takes 5 to 90 volts and outputs a constant 20 mA for powering LEDs. No more current calculations required.

[KenS]

He's using the rectifier as the support structure for the bulb to get it in position for the light tube, and its leads as the contacts to the under-floor power supply.  The constant (low) current coupled with the capacitor will probably ride through some amount of flicker due to dirty track as well. A very clever design.

The one thing I don't get is voltage.  There doesn't seem to be a resistor in the circuit (just the CRD) and yet the LED he's using is limited to 5V.  The CRD would appear to have some voltage-limiting effect, and that appears to be borne out by a page I found discussing testing one (although the translated Japanese wasn't clear and most of it was about the current-limiting behavior).

[CaptOblivious]

He's using the rectifier as the support structure for the bulb to get it in position for the light tube, and its leads as the contacts to the under-floor power supply.  The constant (low) current coupled with the capacitor will probably ride through some amount of flicker due to dirty track as well. A very clever design.

The one thing I don't get is voltage.  There doesn't seem to be a resistor in the circuit (just the CRD) and yet the LED he's using is limited to 5V.  The CRD would appear to have some voltage-limiting effect, and that appears to be borne out by a page I found discussing testing one (although the translated Japanese wasn't clear and most of it was about the current-limiting behavior).

The forward voltage on a diode is just the amount of voltage dropped by a current passing through it; light-emitting diodes, however, are current driven, and not voltage driven. So long as the current fed to a diode does not exceed the limit, then the voltage dropped by the diode will remain in safe limits....even if that current is fed by a high voltage. Which is why constant-current sources are preferable to resistors: Increasing the voltage to a resistor increases the current it passes, and it is the increased current, not the voltage, that produces problems for the LEDs.

Just to give an example. I found a box of LEDs last night in my bits box that were unlabeled. I wanted to know what color they were, and I knew that putting 5 volts across an LED will reduce its lifetime, but isn't itself an issue. What I forgot was that 5V isn't an issue because even at 5V, WITH A RESISTOR, the current allowed to pass is a bit beyond specs, but not much. I've often put LEDs with too-small resistors on a 12V line, and they are very bright but don't drop dead or anything. I just don't reuse them in permanent projects :D

But I didn't put a resistor in series. I forgot. I just took the +5V and GND signals from the USB port on my laptop, and put them to the LED. Results: Bright flash of red (it's a red LED, that's right! THat's why I put them in a red colored box!), and then smoke. And then my laptop bitched that a USB device was using too much power and needed to be shut down. USB is rated to 500mA...which means I just put a half amp through that one LED. No wonder it went up in smoke! LEDs have almost no internal resistance, so I basically created a short circuit. Had I put even a tiny 50ohm resistor in series, nothing bad would have happened, because the current would have been limited to about 60mA, even as the voltage across the LED would have remained near 5V. But I didn't. So I got smoke.

So, just remember: It's the current that's important with LEDs!

[The_Ghan]

lol cap'n

Your story really made me laugh.  I would have at least had the breadboard out for that one !!!

Cheers

The_Ghan

[CaptOblivious]

lol cap'n

Your story really made me laugh.  I would have at least had the breadboard out for that one !!!

Cheers

The_Ghan

It was late at night, and the LEDs were of the 0805 SMD variety...I just pulled out my FTDI cable (USB on one end, +5, GND, TX, and RX lines on the other), and used a pair of handy breadboard jumper wires to touch the +5V and GND signals to the edges of the tiny little thing...*sigh*

[keitaro]

I like the fiber optic type set up but, I don't want it any brighter than the Kato FL11 because the seats are empty. It's just right with the Kato kit.

yes that and it's expensive as hell to fill the train with passengers

[cteno4]

yes that and it's expensive as hell to fill the train with passengers

only $5-6 per car if you cut up the chinese architectural figures!

$144 gets you 5000 figures, should fill your trains! just want to know what you will do with the 10K chopped off legs...

the lighting system looks interesting, i like the use of the rod!

cheers

jeff

[keitaro]

ahh i'm talking about the kato offerings 980 yen a pack = bankrupt

[cteno4]

yeah but thru the windows you would never tell the difference!

jeff

[Webskipper]

That new lighting design with the tube might just work well for long buildings or tunnels.

[cteno4]

That new lighting design with the tube might just work well for long buildings or tunnels.

its currently used on the t scale buildings. each had a central light tube running up the center of the building so you can just put a led under the building to light it up nicely.

jeff