SparkFun Forums

[peterpan]

I have a "looper" pedal I use in my musical performances, and it has a couple of LED indicators, one RED and one AMBER, telling me when I'm in RECORD or OVERDUB mode. Unfortunately these are SMD LEds coupled to the control panel with something like light pipes, and they just aren't bright enough to see reliably in daylight. I wonder if anyone could suggest some replacements that are still small enough that I likely could find a way to mount within the existing pedal. I feel confident I'll have little trouble designing a driver circuit, as the existing LED driver circuits probably won't offer enough current. But here's the thing... I really don't want something that going to require a separate power supply to operate. Of course I want the LEDs to be bright, but they don't have to be bright enough to compete with direct sunlight. I'm hoping to find some LEDs that will make a major improvement , but won't require more than about 50mA give or take. Thoughts?

[UhClem]

LEDs bright enough to be visible in daylight, at currents less than 20mA, have been around for a couple of decades now. All you need to do is pick one from among the many choices. Use the part sorting features at a vendor like DIgi-Key of Mouser to find what you need.

As an example, I used PN SSL-LX5093SRC/E driven with about 8mA in a design to be used outdoors in full sunlight several years ago.

Pick your package and light output and go.

[peterpan]

Thanks David. Thats good to know. I didn't see an amber version of that part. In fact i couldn't find any amber LED that had anywhere near the intensity of the RED one you mentioned. I take it that the 2800 MCD of the part you recommended is a good reference for being decently visible in daylight. But if that's true, the nearest AMBER color I could find in a simple through-hole device was only 300mcd. Maybe it matters less for yellow? I'm not sure. One of my challenges is that I don't have a very good feel for translating "lumens" or luminous "intensity" in "mcd" units into something meaningful. Its one of the reasons I'm hoping to hear of specific parts people have used that have worked in daylight.

[UhClem]

A quick search at Mouser showed amber T1-3/4 LEDs in stock with up to 21,000mcd output. So I don't know what your trouble is. Unless you want a diffused LED in which case the ratings are lower. You may prefer the diffused LEDs because of their wider viewing angle.

I don't have a good handle on converting mcd ratings to desired brightness either. I suggest that you get some likely looking part(s) and connect them to the power source using a variable resistor. Vary the current (keeping it below the LED maximum rating of course) until you get what you like. Remove the variable resistor and measure it. Now you know about what fixed resistor you need.