Resistor soldering/wiring for DCC headlights

[mike_lawyer]

Hi everyone,

I am finally getting around to installing DCC on a Kato Mikado GHQ conversion.  Years ago I installed a micro LED in the headlight position, but did not wire it up.  I now am installing a Zimo decoder, and I just need to install a 1K resistor between the decoder and the LED.  I ordered some SMD resistors, but the solder pads are so small it is hard to solder wires to them.  Anyone have a recommended method and SMD size?  It might be that the SMD resistor I have is too small, so any recommendations would be greatly appreciated!

[peteski]

Mike, what size are the LEDs and the resistors?
If you dont' know and owne a caliper, measure the length and width.

0402 are 0.040" x 0.020"
0603 are 0.060" x 0.030"
0805 are 0.080" x 0.050"
1206 are 0.120" x 0.060"
and so on.

I mostly use 1206 resistors because they have 1/4W power dissipation capacity and are small, yet will solder easily.  But I have used smaller ones too.

Here is a 1206 example with typical 30 AWG decoder wire soldered, and heat shrink cover, but if you were to use enameled magnet wire, it will be even more compact. I use magnet wires in many of my installs.

[mike_lawyer]

Thanks for the info, much appreciated.  I think the SMDs I received were the even smaller ones, those are impossible to solder!  I am going to order the size you recommended.

Mike

[peteski]

Thanks for the info, much appreciated.  I think the SMDs I received were the even smaller ones, those are impossible to solder!  I am going to order the size you recommended.

Mike

The smallest commercially available SMD size component is 0201 (0.020" x 0.010")  and yes, soldering decoder-type wires to its terminals is pretty much impossible. If anything, thin magnet wires would likely be the best option, but getting larger size resistor will likely be easier.

[Sumner]

If you are in Europe it isn't hard to find ....



.... the flexible PCB strips shown above and they work really well for....







.... different type circuits in decoder installs and for other projects.  One use to be able to find them in the UK but not anymore as far as I know.  A friend over there sent me some.  Too bad a distributor like SSB doesn't pick them up.

More info on them and possible sources here....

https://1fatgmc.com/RailRoad/Decoder-1/page-24.html

Sumner

[peteski]

While not really required for Mike's install, I often etch my own PC boards to house resistors and LEDs.  IIRC, those are 0805 size resistors.

[mike_lawyer]

That PCB board strip would be really handy for lighting installs.  I am in the US, I will have to look to find a supplier.

[PanAmShay]

Please share if you find a US source for that flexible PCB strip--looks useful.  Maybe Digikey...