Want to build a piece of LED jewelry (earphones with RGB LEDs)..

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Want to build a piece of LED jewelry (earphones with RGB LEDs)..

Hi forum, Crazy

I’ll be building a piece of RGB LED jewelry. It’s basically a pair of earphones with one or two RGB LEDs on each, with a small ATtiny25-based PWM driver in a small enclosure.

I’ll probably be able to devise the firmware myself; however, since I’m going to have a good few inches of wire going to each phone, I need some sort of LED drivers. I already checked out the LED driver basics and its circuit design (see http://www.apogeeweb.net/article/78.html ) and i know a LED driver would do me a good but that’s where I’m not sure how to proceed.

The basic idea is for all the LEDs to be displaying the same color at a given point. The MCU will fade through all colors in sequence using software PWM. However, I would also like to implement a control for the overall brightness of the LEDs (once ambient noise goes above a certain level, it starts pulsating along with it, kinda like a VU meter). I’m thinking about one PWM-driven ‘brightness’ MOSFET to control the source voltage to the other three ‘color’ MOSFETs. Is this the way to go?

I have a lot of BS170s and not much else in the way of FETs (BF245, 2N5457 JFETs), so that’s probably what I’m gonna be using. I’m thinking of going all-out SMD on this… I only have the tiny25 in SOIC, anyway.

Thanks guys.