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:
- Using a pair of craft tweezers, I roll up the positive leg of the LED.
- Then take the resistor leg and bend it through this loop, then twist it around once. This forms a chain-like connection.
- Solder this connection and then trim the resistor leg back.
- Curl up the outstanding leg of the resistor in a similar fashion.
- 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.
- Curl up the negative leg and solder a 90° bend from another hookup wire to this end.
- 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).