Here's what we did with two of the three modules. At left,
the TD898 module fitted to a blank power point plate. It has
the advantage of a front-mounted "audio in" socket. The hole in
the plate is for an IR receiver (all come with remote controls).
The “Quizzical” game adjudicator (described in SILICON CHIP in September 2011) included a module designed to play MP3 music files – we used it to provide a different sound for each quiz contestant, one which could be changed as required.
As often happens, this project started us thinking about another possible use for the module – that of playing music files “on demand” from an SD or MMC card, USB stick, etc, without resorting to playing them through a PC.
First, a bit of background. The idea for this came from a colleague who manages a public hall, often used for wedding receptions, 21st birthdays and even corporate and public meetings.
More often than not (especially for receptions and birthdays) those using the venue wanted to play music files through the hall’s PA system.
If they provided them on an MP3 player with headphone output, no drama – the PA had been rigged with a “line in” terminated in a 3.5mm plug.
At right is the TD896 module mounted in a small box - it's our fully portable version. We chose this module because of its overall small size.
But just as often, someone would produce a USB stick (or sometimes a memory card) and ask if they could play the music they’d stored on those.
The manager usually obliged by plugging in his laptop computer and using that to read the stick or card. But apart from the security risk of leaving his laptop when he wasn’t there, it was a lot of mucking around. It also meant he couldn’t use his laptop that day or evening!
He’d seen the Quizzical and asked if there was some way its MP3 ability could be adapted to provide this “service”.
And then we thought, why not go one step further? If you mounted a plate containing one of these modules on (or even in) a convenient wall and connected it to your hifi system or home theatre amplifier, you’d have five-second plug-in convenience if you ever wanted to play music you’d previously saved on a USB or SD! And a lot of people want to do exactly that!
Not exactly practical
On closer examination we decided the module used in the Quizzical, a TDB380 from Tenda Electronics, was not really suitable. Sure, it would read the files stored on an SD card – but it needed some “smarts” (eg, the rest of the Quizzical!) in order to select the right track(s) and so on.
Not only that, it didn’t have other features that we really wanted: a USB interface, for instance, nor would it take an audio input if someone did bring along their MP3 player (or even their own cassette recorder). The TDB380 would need quite a lot of work and additional circuitry to bring it up to the mark. Scratch that idea.
Here are same-size top and bottom views of the TD896 module showing connections – the top side if you wish to use JST connectors and the bottom side if you wish to solder direct to the pads underneath.
The speaker connections can be ignored if you don’t want to use headphones or speakers.