LED Wiring

This is a basic ele­ment of many elec­tron­ics projects: how to wire up an LED with a cur­rent lim­it­ing resis­tor. Most effects have a 5 mm LED and many wiring dia­grams show a 4k7Ω resis­tor. There’s a fair­ly wide range of val­ues you can use, depend­ing on how bright you want the LED (and what the LED’s specs are). You can cal­cu­late out the exact val­ue to use if you have the specs for an LED, but using a 4k7Ω works well enough for most situations.

What’s a bit less obvi­ous is how to sol­der a resis­tor’s legs to an LED leg and the con­nect­ing wires. Here’s my method:

  1. Using a pair of craft tweez­ers, I roll up the pos­i­tive leg of the LED.
  2. Then take the resis­tor leg and bend it through this loop, then twist it around once. This forms a chain-like con­nec­tion.
  3. Sol­der this con­nec­tion and then trim the resis­tor leg back.
  4. Curl up the out­stand­ing leg of the resis­tor in a sim­i­lar fashion.
  5. Bend the tinned tip of your hookup wire at a 90° and hook around this loop to sol­der just like you would a jack con­nec­tion.
  6. Curl up the neg­a­tive leg and sol­der a 90° bend from anoth­er hookup wire to this end.
  7. Apply heat-shrink tub­ing over both con­nec­tions. I picked up using the bar­rel of sol­der­ing iron from Collin of CS Gui­tars.

You could do NASA-spec sol­der joints if you want, but this is typ­i­cal­ly more than strong enough for con­nec­tions. As for the resis­tor, it does­n’t real­ly mat­ter which leg you attach it (that is, before or after the LED in the cir­cuit) as it will have the same effect. How­ev­er, by def­i­n­i­tion, cur­rent will only flow through a diode in one direct, so it does mat­ter that you have the LED leads clear­ly iden­ti­fied. That’s why I try to be con­sis­tent with using red as the pos­i­tive (and typ­i­cal­ly black for the neg­a­tive, but I was out of black hook-up wire dur­ing this par­tic­u­lar project).