Oscillator circuit??

Discussion in 'The Projects Forum' started by djreiswig, Jul 2, 2011.

  1. djreiswig

    Thread Starter Well-Known Member

    Aug 8, 2008
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    I have an automotive cassette player that I am trying to hack the electronics from and use to make an mp3 player input for my car stereo. It is a factory stereo so it needs some of the electronics in the aux cassette player for the audio ports to open correctly. I would like to remove all of the tape related components (motors & gears) and just use the electronics. The problem I am having is there is a gear inside the unit that has a shiny disk with pie segments alternating black and white. This disk rotates when the cassette is playing. There appears to be some sort of photo sensor mounted above this disk that detects if the disk stops spinning indicating the tape has run out or is jammed. I would like to remove this sensor and replace it with some other components that will not require the motor to spin.

    I'm not sure on the specifics on this sensor/disk combination as far as what the limits are on the speed of the changing of the colors. I would probably need a circuit that has some adjustability at least initially.

    I can take some pictures of the sensor if that would be helpful.

    The cassette player is a Delco remote mounted unit used in several GM vehicles. Examples of this unit can be found on eBay.

    Any ideas on how I can make this work?

    Cross posted here:
    http://www.electro-tech-online.com/...-ideas-reviews/120058-oscillator-circuit.html
     
  2. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Let me get this straight, essentially you want to play your MP3 player through your car stereo but by using an old cassette player as some sort of intermediary device? This seems like a huge space issue along with a lot of unnecessary electronic parts.
     
  3. HarveyH42

    Active Member

    Jul 22, 2007
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    There are cheap cassette adapters, which I've used in the past, when the player gets to the tape eating phase. There also FM transmitters, not too expensive either... Since your cassette is remote mounted, should be some input into your stereo, why bother with the cassette player. Could understand, if it were in dash, and removing it, leaves a huge gaping hole...
     
  4. djreiswig

    Thread Starter Well-Known Member

    Aug 8, 2008
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    iONic: The cassette player is a remote mounted unit that came in some cars. My factory stereo has a connection to interface with this unit. The car did not come with a remote mounted cassette player, but I purchased one from a salvage yard. I can not interface with this connector directly, as the stereo will not recognize anything but the cassette player. So, if I connect the cassette player, I can intercept the audio wires and play an mp3 player through it.

    HarveyH42: I have heard that the cassette adapters and FM transmitters do not work that well. Yes, the cassette is remote mounted, or would be if it originally came in my car. There is a cable that connects it to the stereo. As I said above, there is some sort of serial connection will only work if connected to a cassette player. So I need to have the cassette player electronics (I play on removing the unnecessary parts) to fool the stereo. There are adapter cables available that use this setup, but they need a cassette player with a cassette playing in order for the connection to open. I believe it is probably because of this spinning disk unit. If I can emulate the disk, I believe I can get this to work.
     
  5. debe

    Well-Known Member

    Sep 21, 2010
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    The FM transmitters work very well been using one now for about 4yrs.
     
  6. djreiswig

    Thread Starter Well-Known Member

    Aug 8, 2008
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    That's great. I still would like to try and get this cassette thing to work. Does anybody have any ideas on how to replace this spinning wheel thing with some electronics?
     
  7. iONic

    AAC Fanatic!

    Nov 16, 2007
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    There may be a sensor that detects the presence of a cassette and enables the signal through. Also, the Tape head that the cassette tape slides across is what picks up the signal. the wires connected to this head are where your input signal from the MP3 player would connect. Have you done an internet search for such a hack?

    A couple of links that might be of interest:

    Car Stereo iPod Input Hack

    Amstrad Shuffle

    Audi Concert Autopilot Hack

    http://eclecti.cc/hardware/normal-people-dont-have-these-problems
     
    Last edited: Jul 4, 2011
  8. djreiswig

    Thread Starter Well-Known Member

    Aug 8, 2008
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    Yeah, I've searched a lot for this type of hack. I haven't found anyone that has tried to get rid of the tape stuff out of a remote player. The tape detecting stuff is just simple toggle switches, that I can short or open depending on the correct state they should be to think a tape is there. I believe this rotating black/white sensor is the only thing I have yet to figure out. I'm sure the deck needs to see some sort of switching input the entire time the tape is playing or it will pop the tape and cause an error.

    I looked at your links, but they didn't seem to help. I have seen a few places where people hack into the CD wires and play a CD and switch the audio channels to the aux input. I could do this, but I wanted to try and get the tape thing to work since there is a button on my stereo to switch to the aux deck. Then I wouldn't have to hack into my stereo, just plug and play.

    Here is a deck like the one I am hacking.
    http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=400131638543
     
  9. iONic

    AAC Fanatic!

    Nov 16, 2007
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    How about a picture of this rotating b/w thing-a-ma-jigi!
     
  10. djreiswig

    Thread Starter Well-Known Member

    Aug 8, 2008
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    I'll post a pic tomorrow if I get the chance. Basically it is a circle with pie segments in alternating colors. I think about 3/4" or so across. It is attached to a gear that meshes with the gears for the tape reels. The sensor is 2 parts next to each other on a circuit board that floats above the spinning gear. It looks like each part has 2 wires. I suppose it is a photo sensor and a light transmitter?? I haven't tried yet, but I was going to try shorting one side with a fused wire to see if I could duplicate the pulse. I'll have to try and determine which one is the receiver. I haven't hooked this thing up yet to play with it and see it in action.
     
  11. ifixit

    Distinguished Member

    Nov 20, 2008
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    Hi djreiswig,

    It sounds like a sensor to detect the end-of-tape to know when to stop, or reverse, and play the other side.

    One idea, to try and defeat this function, would be to mount some of the reflective material permanently in front of the device so that the photo sensor always sees the photo emitter signal. Then hack the circuit and modulate the photo emitter diode signal with the output from an 555 timer set for a square wave and a frequency you estimate to be equal to the rotating disk pattern.

    Alternately, you could remove the device completely and carefully drive the photo detector signal amplifier directly. This would be more difficult because you have to figure out what the right amplitude of signal would be best.

    Sounds like a fun project,
    Ifixit
     
  12. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    950
    The cassette audio adapter units. The ones that look like a cassette can be found at the local 99cent stores. I've seen them in several different stores here in town.

    GET ONE. This is the easiest way to 'fool' the cassette player.

    Then you can easily hack into the audio output traces on the PCB of the cassette player and connect the MP3 audio into the unit. You may have to build a voltage divider to lower the audio pk-pk level if you have audio distortion upon playback.
     
  13. djreiswig

    Thread Starter Well-Known Member

    Aug 8, 2008
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    ifixit: Sounds like you've hacked a tape deck before. Yeah, I suppose it could be to tell the deck when to flip the tape. I haven't tried hooking it up to see exactly what I need to defeat. I just thought that the little spinny thing looked important. I'll try and get out to my car and get the cable hooked up and see what I have to do to make it function without a tape.

    Kermit2: I thought of just leaving a tape in it and hiding it somewhere under the dash, but I didn't see the need to have the motors and stuff spinning when I don't need them. Besides, where it the fun in that.
     
  14. djreiswig

    Thread Starter Well-Known Member

    Aug 8, 2008
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    Here are some pics of the spinny sensor. Kind of hard to see. Hope it helps. I haven't had a chance to hook it up to the stereo to see what happens. The first two show the sensor. It is black and toward the left edge of the board (bottom in the second picture). There is also a gray gear that has some wires going to it. It meshes with the tape loading mechanism. I assume it tells when the tape is in all the way. The right picture shows the shiny gear thing toward the right. It appears to mesh with one or the other of the spindle gears. I assume it stops when the tape has run out. I am thinking it need to have a signal in order for the stereo to think the tape is still playing. I'm just guessing on this as I haven't actually tried it out yet, and I haven't found much information on the guts of these things. Just thought I'd give you guys a look at what I have.
     
  15. djreiswig

    Thread Starter Well-Known Member

    Aug 8, 2008
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    Okay, I hooked it up today, and it looks like the little spinny think doesn't have much to do with the player opening the aux port of the radio. I hooked up the 3 circuit boards from the cassette player to the stereo, and it switches to cassette mode. When I plug/unplug one of the cables between the main board and the second board I can hear scratchy noises from the speakers, so I assume this is the audio cable. There are 2 switches and the tape loading gear thing that appear to sense where the cassette is in the loading cycle. The gear thing has 4 wires that connect in various combinations depending on where the gear is rotated.

    I played around with these in different combinations, but can't seem to get it to function the way it should. It will show the tape icon on the radio and switch the input, but when I switch the radio back to FM, in about 20-30 seconds it switches back to the tape. This continues until I unplug the player. I must not have the switches and gear in the correct alignment. I think it is the gear, but unfortunately I didn't look at its position before I took it apart.

    I guess I'll chuck it in a box and forget about it for a while. I'm tired of messing with it.

    Thanks everybody for the help.
     
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