Car MP3 Player #1


Obsolete project for reference only

This project has an impossible requirement or uses parts that are no longer available. It is here for reference or inspiration only. Consider it “unsupported”.

Yet Another Mobile MP3 Player

End View

End View

When I got a new car in 1998 I built a player after deciding MP3 sound quality was good enough. Near the end of 1998 I had this player built and in service. For over a year I had no real remote control for it, and used a TRS-80 model 100 to control it. I didn’t finish the wired remote control until 2000. The player fits under the passenger seat.

These pictures were taken during the final assembly stages. The dimensions are approximately 11 by 9 by 2 inches. I made the case from aluminum sheet and painted it with textured “trunk paint”, which hides mistakes nicely. The case contains a Tyan Titan III motherboard, right angle ISA riser card, 3Com 3C509B ethernet card, Soundblaster Vibra 16 sound card, Maxtor 3.5 GB disk, and a 12 volt power supply I built to fit. It’s basically a personal computer that runs in a car.

Top View - Cover Off

Top View - Cover Off

The CPU is an AMD K5 running 75 MHz. There’s 16 meg ram, and the operating system is Linux (Red Hat 5.2). MPG123 handles the MP3 decoding, and I wrote a control program in Perl.

Remote Control

Remote Control

I built the remote control in an old Blaupunkt CD-changer remote case which I emptied completely. It now has a backlit 40×2 LCD and a PIC 16F84 microcontroller. It communicates serially at 2400 baud and also turns the player’s power supply on and off. It has a few inputs and can sense if the car stereo is on.

The old Tyan motherboard takes a long time to self-test, and a 75 MHz processor isn’t very fast. Booting takes 90 seconds. I thought it would be neat to use one of the remote’s sense inputs to sense the electric door lock on the car, so it could start booting before I got into the car. The car’s wire I needed to intercept was hard to get to, so I never bothered. It would only save a few seconds anyway.

This player has survived winter in central Oregon and summer in Phoenix. Before I built the remote I’d have to manually turn the power off, and sometimes I’d forget. I could still start the car after running 15 hours on the battery, and it also survived a few weekends when it drained the car battery to nothing. The battery didn’t like that so much. In 2002 I built a faster, smaller player and gave this one to a friend. It still works fine and will be getting a larger capacity disk some day.

Power Supply Schematic Diagram

Power Supply Schematic Diagram

You can click on these for bigger images or for printing/downloading.

Remote Schematic Diagram

Remote Schematic Diagram

Files:

MP3 Playing Software (perl)
Remote Control Code (C)
Remote Control Firmware (hex)