# Hacking CD players



## Otaku (Dec 3, 2004)

Hi all,
This year I noticed that a moderately enhanced sound file (echo, minor distortion effects) can really mess with servomotor action. My reaper's jawbone sometimes looked like he was shivering. Since the ISD chips don't record in stereo, I need something that gives me a way to play the modified sound through his speakers while sending a clean sound file to the servo driver board. Does anyone here know of a hack that can allow a CD player to be started in play mode when triggered by a PIR or similar device? I know there will likely be a small delay between triggering and playback, and that's OK; instant-on is not needed. Thanks!


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## gmacted (Jan 18, 2006)

That's a very good question. I know of no way to easily hack a stand alone unit, but I wanted to try and hack a 



. I think you could use a PIR with a transistor and relay circuit to trigger the remote control to start the CD player. I've never tried it, but I'm sure it would work.

I'm thinking about using a ump3 player in a prop for next year. It has stereo output and can be controlled using a prop1/prop2 controller. I used a prop-1 this year with a mono channel AP-8 and a relay to drive two different speakers in two different locations. Only one speaker can be on at one time, but I think you get the idea. Using the ump3 player and a relay will be able to give me four channels of output. I will only be able to play two channels at any one time, but I think the effect will be great.


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## Zombie-F (Apr 12, 2004)

The uMP3 is GREAT. You can control it serially by the prop-1 or even just trigger individual sounds by bringing certain pins on it to ground. I controlled an AP-8 and a uMP3 with the same Prop-1 so I could have three characters interacting with one another. It worked out perfectly. 

As for hackable CD players... maybe hacking a cheapie mp3 player would work well too.


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## Otaku (Dec 3, 2004)

Thanks for the tips. The uMP3 is a bit pricey for me, but it sure would fit the need. One of the problems with cheapo CD players is that they'll shut down if left in "stop" mode for too long, so I'd need to think about how to disable that feature. I looked at the $5 16MB MP3 players but without actually playing with one, it's difficult to say what would need to be done to it. I'll post whatever progress I make on this.


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## HibLaGrande (Sep 25, 2005)

could use two isds one with the clean sound to run the servo controler and one with the effects to go to the speaker and have them both triggered at the same time??


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## Otaku (Dec 3, 2004)

Good suggestion - I've considered doing that but want to use a better quality sound source. I may pick up a couple of those $5 MP3's I mentioned earlier and tear one up. The product sheet says you have to hold the Play button on for ~3 secs. to start it, but I've got just the thing to handle that part.


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## HalloweenRick (Nov 25, 2005)

Hey Otaku any word yet on hacking a cheap MP3?


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## Otaku (Dec 3, 2004)

Yeah, I got a couple of the MP3 players and I've been working on a timer circuit. Here's what I've got in mind: one 555 timer circuit set at ~3 secs. to start the player, a second 555 timer to handle the power to the player. Both start at the same time, when triggered by a mat switch, PIR or whatever. T1 starts the player, T2 is set for the length of the sound file. When T2 runs out, power is cut to the player, and it waits for the next trigger event. These players will repeat the sound file if not turned off, and I learned that there is a small output voltage drop between playbacks. If I can find a gate IC that can detect the drop, the shut-off can be automated regardless of the file length. I'll be ordering the parts to build the timers next week. More to come.


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