I used an old IBM Personal Computer 360 - Pentium 75 that I got from a friend. Although the motherboard can handle faster processors I see left it as-is, for quite a while. The performance of DOS + MPXPlay + My frontend software was more than adequate, at the time. No reason to upgrade to a faster CPU that draws more power and creates more heat, when there's no compelling reason to do so. The motherboard has a proprietary form factor and uses a riser card. The card has 2 shared PCI/ISA slots + 1 ISA-only slot. The motherboard has on-board video (S3). Nothing fancy, but it's more than adequate for troubleshooting/debugging purposes.
The machine came with 32 megs of memory, which was way more than was needed. I downgraded it to 16 megs. Out of the 16 megs of remaining memory, the software doesn't even use half of that. I chose to keep the 16 megs, and devote half of it to a disk cache.
For sound, I planned on using a Sound Blaster 16 sound card. The card worked ok, but the sound quality was a bit disappointing. I replaced it with a cheap Pine Technologies ISA sound card, which is based on the CS4235 sound chip. It was a pain to set up. The card did come with DOS drivers, but the installer only would run from windows. (see the download page if you need them) Then the default settings didn't work too well. In the end I did manage to get it to work with MPXPlay in WSS mode. I used the following settings:
c:\crystal\cwdinit.exe /o /c c:\crystal\cwdaudio.wcm
I started out using a 3Com 3C509 Etherlink III 10 megabit card. It worked flawlessly, but was a bit slow.
Feeding Sound to the Car
Rather than lose sound quality, using a cassette adapter or FM modulator, I wired it direct into my car stereo's passive equalizer. Since I didn't have a switchbox, I was stuck swapping cables whenever I wanted to switch between the radio, CD changer, and the computer.
I'm using a Matrix Orbit 20X4 LCD character display. This LCD uses a RS232 serial interface. These units come pre-assembled, complete with a 9 pin DIN connector. This keeps the cabling simple and straight-forward. In addition, the display is backlit, so a person can see it at night.
Out of the many options available, I chose the Gravis Gamepad Pro joystick. It's less cumbersome than a keypad, still has an adequate number of buttons, and unlike a wireless remote, I don't have to worry about losing it.
DC/DC Power Supply
I made the decision use a DC/DC power supply, instead of an inverter, fairly late in the project. I chose the DC/DC power supply for two reasons:
- 1) Inverters can be a bit noisy; noise and audio don't go well together.
- 2) The price difference isn't as large as I originally thought.
A number of the people, who visit the MP3Car.com forums, recommended the Arise ACE 865-V. Another site recommended shelling out the extra money for the ACE 890-V, if the system is a pre-MMX Pentium. Evidently the pre-MMX Pentiums draw more power off of the 5V line.
With "Murphy's Law" in the back of my mind, I decided to do some testing. I purchased an AT power supply extension cable, and an extension cable for the hard drive's power connector. That way I could cut the wires on the extension cables, instead of cutting up the power supply's wiring.
I tested the +5V lines that run to the motherboard, the motherboard's +12V line, and the hard drive's +12V line. The motherboard draws a steady 3 amps on the +5V line once the machine is booted; 3.5 amps during the power-on-self-test. The motherboard draws less than .5 amp on the 12V line. I found that hard drive draws close to 2 amps while spinning up, but only .5 amps the rest of the time.
In the end I chose the ACE-890V but for a different reason than I thought I would. It turns out that both the 865 and 890 are adequate for the processor/motherboard combination that I'm using, but the 865 only provides 2.5 amps on the +12V line. This would limit me to only 1 hard drive. The 890, on the other hand, can supply up to 4 amps on the +12V line. The specifications of both models of Arise power supplies can be found here
The Arise ACE 890-V doesn't provide a +3V or a -5V output. The proprietary IBM power supply does. However, after doing some testing with both the +3 and -5V lines disconnected, the system still worked normally.
While ordering the power supply the sales representative asked which power cable I wanted. I chose the P8/P9 cable. This cable will work with most machines that use AT power supplies.
I wanted to be able to power the computer from the car, but also wanted to be able to power it from the AC house current. A simple way of achieving this would involve using the AC/DC power supply's 12V output to power the DC/DC power supply. Then a simple relay could be used to switch the DC/DC's input between 12V output of the AC/DC power supply, and the power connector used in the car.
Sounds great in theory, but the AC/DC power supply that I'm using doesn't supply enough current on the 12V line. Since the holes have already been cut for the propriatary AC/DC power supply I was pretty much stuck with it.
I ended up getting a DPDT relay and another 4PDT relay to switch between the outputs on the two power supplies. An AT power supply extension cable was cut in two. Wires were run to the relay (1/2 of the extension cable to one set of inputs on the relays, the other half to the outputs). Then another set of wires were ran between the DC/DC power supply and the relay. Finally the grounds were wired together.
This method worked, but involved a lot of wiring, soldering, and hours of work. I'd strongly recommend not using this method of wiring unless there is no other choice.
|Maxtor 80 gig hard drive (bought in January 2001)||Compucheap||$290|
|Promise Ultra 66 HD Controller Card||TechStore||$23|
|Linksys LNE100-TX 10/100 Ethernet Card||Worst Buy||$25|
|Soundblaster Vibra 16 Sound Card||Already Had It||$0|
|Circular Saw Case||Fleet Farm||$30|
|Arise ACE-890V DC/DC Power Supply||Arise Computer||$98|
|Matrix Orbital 2041 20X4 LCD Display||Jameco||$90|
|Gravis Gamepad Pro||On Cue||$20|
Mount 8-32 M/F Thread
|Sorbothane 4" X 4" 1/2" thick 40 Durometer||McMaster-Carr||8514K115||$6.40 ea.|
|10 Gauge Red Power Wire||Parts Express||100-160||$.38 / ft|
|10 Gauge Black Power Wire||Parts Express||100-162||$.38 / ft|
|Scosche Inline Fuse Holder||Parts Express||263-327||$4.50|
|Phoenix Gold ARx.360 20ft RCA Patch Cable||Parts Express||263-408||$9.90|
|12VDC Automotive Relay SPDT 30amp||Parts Express||330-073||$.99|
|Gold Plated Ring Terminals 10 gauge 5/16" 2 Pair||Parts Express||095-665||$1.10|
|D-Sub 9 Pin Female Connector||Jameco||15771||$.49|
|D-Sub 9 Pin Male Connector||Jameco||15747||$.35|
|9 Pin D-Sub Metalized Hood||Jameco||25620||$.45|
|D-Sub 15 Pin Male Connector||Jameco||15034||$.45|
|D-Sub 15 Pin Female Connector||Jameco||15051||$.49|
|15 Pin D-Sub Metalized Hood||Jameco||25566||$.45|
|100ft 24 Gauge 4 Conductor Shielded Cable||Jameco||31860||$14.00|
|10 Female Standoffs 4-40 thread .375"||Jameco||77500||$1.70|
|100 4-40 Machine Screws .25"||Jameco||40951||$1.60|
|10 .100" Connectors 2 contacts||Jameco||100811||$1.50|
|20 Female Pins||Jameco||100765||$2.00|
|6" X 3" X 2" Project Case||Radio Shack||270-1805||$3.69|
|Coaxial DC Power Plugs 5.5mm O.D. X 2.1mm I.D.||Radio Shack||274-1569||$1.69|
|Coaxial DC Power Jack 5.5mm O.D. X 2.1mm I.D.||Radio Shack||274-1582||$1.99|
|Coaxial DC Power Jack 5.5mm O.D X 2.5mm I.D.||Radio Shack||274-1583||$1.99|
|DPDT 12VDC Relay||Radio Shack||275-0218||$7.99|
|4PDT 12VCD Relay||Radio Shack||275-0214||$7.99|
|High Current Power Connector (Male)||Radio Shack||274-0151||$.99|
|High Current Power Connector (Female)||Radio Shack||274-0154||$.99|
Last Update: 12-22-2006
Copyright © 2001-2018, Brent Harris
All rights reserved.