LED Conversion Flickering Proble

Did you try reducing the brightness using John's module first?

No, I built his diy module after purchasing his recommended components. I've been thinking that the 220 ohm resistor may need to be moved across the led strip + and - terminals on the led light strip instead of the common ground wire feeding the 220uf 50v capacitor. I'm hoping that GRJ or one of the electronic gurus could offer some expert advice to help solve my problem. 

Perhaps posting EXACTLY what circuit you're using and how you're connecting the LED's would help.  I'm especially curious about the 220 ohm resistor.

Here's what my currently available lighting modules have as a circuit, and I have no complaints about flickering LED's.

Hi John.

I'm attaching the 220 ohm resistor to the negative lead side of the cap where the common track lead is attached. I've also utilized your PTC component recommendation on the roller wires feeding the choke side of your module. Thanks for the quick reply.

Bill Swenson

John,

This module was based on your 5/21/14 OGR posting. I purchased    all of the components back then and was just recently embarking on the project. 

Bill

What are all those other components besides the resistor? There should not be anything other than the diy module needed. The module limits current to the leds, so no further resistor is needed. Brightness adjustment is done on the diy board.

Rod

Sorry I thought you were refrring to the new modules discussed earlier this year, but I see you are referring to a 2014 topic. John will provide comment.

Rod

Hi Bill,

This may be overkill to some but I do mine a little differently. I take the power from the track into a small 1 amp full wave rectifier, I then connect one of the cheap DC adjustable regulator boards from the auction site, and on its output I connect a 1000 mfd cap and then connect my led strip. I get no flickers and when power is removed from the track it takes several seconds for the leds to go out.

Ray

The "resistor" you speak of should be a 22uh RF choke for DCS  compatibility, not a resistor.  I'm assuming that's the CL2 regulator module you're using.  If so, with a choke that circuit should work fine.

John,

On the positive side of the module is the 22uf choke resistor, 1N4003 diode, CL2N3 regulator and a 220uf 50v cap. When I attached the regulator + and the cap - side to the led strip the brightness was too intense, so by trial and error the 220 ohm .25w resistor connected to the common track lead to the cap seemed to work just right. Please confirm that my hot roller wire should go to the choke side of the circuit and the common wheel ground should go to the cap - lead side. I had tried the 1000uf resistor across the led + and - leads with no apparent effect.  Is the 220uh resistor lowering the voltage too low for the cap to charge up properly? Thanks again for your assistance.

Bill

Now it all comes in focus.  You're dropping a lot of voltage across the resistor and thus causing the CL2 regulator to fall out of regulation because of lack of input voltage.

Instead of putting resistors in series with the track power, parallel resistors across the LED's to shunt part of the current, that will achieve the result you're trying to get and eliminate the flicker.  The CL2 is a constant current device, so it's bound and determined to supply it's rated current to the output until it's input voltages falls too low, that's why you can't do it the way you're doing.  You'd have the same problem with a plain voltage regulator, it would have a similar issue, just with voltage.  I'd start with something in the 470 ohm to 1K range to start.

BTW, a choke is a choke and a resistor is a resistor.  The chokes value is in henrys (or fractions, in this case micro-henrys).  Resistors are rated in ohms.  Using the correct terms will lead to less confusion when you're discussing circuits.

John,

I'm so sorry about about my misuse of component measurement terms. I realized my mistakes after I sent you my previous reply but figured you would know the difference. I'll work harder in the future to use the proper terminology. I should not have deviated from your original module design by adding that darn 220 ohm resistor. Now it's back to redoing the 12 finished passenger cars to correct my error. I did not want to continue with this project until the led flickering project was resolved.  Thanks so much for your help and hope to see you at the York meet.

Bill

wmswen posted:

John,

I'm so sorry about about my misuse of component measurement terms. I realized my mistakes after I sent you my previous reply but figured you would know the difference.

No apology necessary, just like to keep things correct so people don't get confused and start assuming things that don't exist.