Desktop·25,124 discussions

Need a momentary contactor (if they exist) or something!

Tags: Hardware, Hardware

So I want a Mp3 file to play the moment my PC powers on.

I am currently buying al the parts to build this PC. I plan to tap into the 3.3V signal going to some LED’s on the power button or something for example. I want that to trigger a play signal for a Mp3 module board hooked up to a usb power supply dedicated for it and wired to a 3w/4ohm speaker inside the case. I can handle all that.

The problem I am running into is this: Most of these boards have two points to solder on to open/close the circuit for play/pause. BUT upon a long press it will go into settings/mode or something. And also I’m worried if the contactor stayed closed (since the led would stay on) that the Mp3 would loop. I want neither. So I need to turn a 3.3v signal into a trigger for a Mp3. If there was some sort of momentary contactor that would snap open->close (or visa versa, just swapping states twice) upon receiving power that would be PERFECT. Ideas?

Topic

Copy from the CNET Forum.

In reply to Need a momentary contactor (if they exist) or something!

From TATUNE’S post on CNET:

Title: I take it you have more than a basic grasp of electronics.

Here’s something I might pick to do that trick.

This is what I’m using.

In reply to Need a momentary contactor (if they exist) or something!

So I figured this out. Products used linked at the end.

I found a timed relay that gets triggered by anywhere from 3v-30v. Also the Mp3 module would play upon powering up. So, off the PSU of my pc I’ll be using a molex->female usb wire, and then a usb-double tail micro usb. The first micro usb powers the contactor. The second I splice the wire open and grab the +5v wire (red in my case) and interrupt it, running through the N/O side of the contactor. And plug the interrupted 5v micro usb into the mp3 module to power it when the circuit is closed. I then obviously load the mp3 I want to play onto a fat32 formatted sd-card, insert that into the mp3 module and wire in the speakers. I set the timer on the relay to only open for the length that my Mp3 file is.

From there I’m going to tap into the ~3.3v wire that turns on with the LED for the front IO panel power button. That means when the PC turns on, that light turns on immediately, that triggers the relay to close for ‘X’-seconds, that powers up the module to immediately play an Mp3 file, and then turns the mp3 module back off when it’s finished. This relay will only run once per time it receives power, and not loop.

Timed Relay

MP# module

Speakers

SD card

[Author]

Replies