Help with changing the speed of a walkman motor with motion sensors

Discussion in 'The Projects Forum' started by foundry, Aug 4, 2013.

  1. foundry

    Thread Starter New Member

    Aug 4, 2013
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    Hi,

    This is my first post here. I am an artist and i do a lot of work with old formats, such cassette tape, VHS, video 8 etc. Recently i have started to have an interest in trying to further manipulate these formats and to experiment with the properties of the machinery itself. I was hoping someone may be able to shed some light on a problem i'm having.

    I'm currently working on an interactive art installation and my goal is to alter a series of old walkman cassette players so that as people move around them, the speed of the motor changes, and in turn so does the pitch of the tape.

    I know that when walkman batteries become weak, the motor, and in turn the tape gradually slows down. This is the effect i would like, but so far i've only been able to shut the motor down entirely.

    Essentially i would like it so that the closer someone is to the walkman/sensor(s) the speed slows down, and when they move further away, it returns to normal.

    I thought that using a motion sensitive potentiometer of some kind may work, but i'm really lost as to what components might be available for this, and whether this could create a slowing down effect, or whether it would just again, switch it off.

    I did already try an LDR, but i wasn't able to cause any effect. I also fear, that since the installation is in a light space, an LDR won't be able to discern the very slight changes in light, particularly if people aren't very close. I feel motion detection, is the way forward, but i'm really lost there. I'm really not very experienced in electronics.

    The walkman runs off two AA batteries.

    It seems like a simple idea, but perhaps it's something that's actually quite complex to achieve. Either way, any light anyone could shed on this would be a real help to me.

    Thank you!
     
  2. MrChips

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    Oct 2, 2009
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    It is doable but would require some electronics wizardry.
    Firstly, I would assume that the Walkman has to have some kind of motor speed control in order to keep the speed constant. This is usually built in the motor itself in the form of a governor-switch mechanism. You would have to dismantle the Walkman and see how this is done. Then you have to disable this speed regulation.
     
  3. foundry

    Thread Starter New Member

    Aug 4, 2013
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    Hi MrChips,

    Thanks so much for your response. If it is possible to achieve, i'm very much willing to try and get to grips with it.

    I have managed to dismantle the walkman to some extent - in terms of identifying this mechanism, what exactly would i be looking for on or around the motor?

    Also, as i mentioned i have noticed that when the batteries become weak, the speed slows down; would a potential option be to somehow vary or impede the voltage being delivered from the battery?

    Thanks again, really appreciate your help
     
  4. MrChips

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    I have never owned or taken apart a Walkman.
    I have seen the motor on a portable tape recorder.
    The motor has a switch internal to the motor housing mounted on the shaft.
    There is a screw adjustment to adjust the speed of the motor.

    I have no clue what they do on a Walkman.
     
  5. MrChips

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    Oct 2, 2009
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    Does your motor look like this?

    [​IMG]


    This looks like a pancake stepper motor and the speed is controlled electronically.
    It would be a challenge to modify the circuitry without some knowledge of the electronics or a schematic. Access to the system clock would allow you to change the speed.

    Maybe someone can supply a schematic for this.

    Edit: I have found a service manual online and looking it over now.

    What is the model number of your unit?
     
  6. GopherT

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    Nov 23, 2012
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  7. foundry

    Thread Starter New Member

    Aug 4, 2013
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    The model of the one i'm experimenting with is a Ferguson Escort, it's quite an old one i think. The motor does look very similar to the one on the picture, perhaps a bit more stocky.

    I also have access to a Sony WM-FX433 and a Panasonic RQ-P202.

    GopherT, thanks for your response.

    Originally i did consider using a Theramin, but i wasn't sure if it would be powerful enough to detect motion from bodies in the space. The area in which i would like to detect motion would be approximately 2.5m x 2.5m

    I did also consider building one, another artist friend of mine did mention that he built a large one for a show, but i was afraid it might be slightly beyond my skillset to use it to effect the cassette player in this way. What do you think?
     
  8. foundry

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    Aug 4, 2013
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    I'm not sure how i missed this article in my searches, but somehow i managed it:

    http://ofsoundmind.wordpress.com/2008/01/24/primer-pitch-bending-a-walkman/

    Essentially he details exactly what i'm trying to achieve, but with the use of a physical potentiometer.

    With this info I think i should be able to get to the stage where i can adjust the pitch, but still the real problem seems to be how i can affect this adjustment via motion.
     
  9. MrChips

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    The technique you end up with to modulate the tape speed will very much depend on the particular tape player.

    Your best bet would be to modify the Sony WM-FX433. The service manual is available and the adjustment is a simple 4.7kΩ pot.

    btw - Walkman is a trademark of Sony.
     
  10. wayneh

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    Sep 9, 2010
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    Do you want more than just two states? It sounds like you do, in which case you need some form of range finding. Ultrasound may be the best bet.

    You could probably do near and far (2 states) with just a PIR motion detector, like a security light. But I don't think it can judge distance, just the presence or absence of motion. Maybe someone has a clever way to get a proportional signal out of it.
     
  11. GopherT

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    You could use ir emitters and photo- transistors (photodiodes) in a reflection mode. Sharp makes similar devices as a module but you could pulse the emitters at about 10k Hz. Then mount the photodiode right next to the emitter and look for a reflection. You should be able to 'see' about 1 meter away. Use a filter on the receiver (photodiode) to block DC room lighting or anything below 1k Hz. Use low gain to get a good Dynamic range (too high of gain will give a binary on/off with no differentiation for distance).

    You could place a dozen or so around the object d'art and get different tones. Multiple people could influence the tone.

    Alternatively, you could design in a binary (on/off) system that will ultimately output true musical notes.
     
  12. foundry

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    Aug 4, 2013
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    MrChips, thanks again. I have the FX433 and an FX423 so i will set to work on modifying those two. I'm not sure i will understand much in the service manual, but it's certainly a help to have it.

    wayneh - Yes, i would like more than two states. I would like the pitch to change in relation to movement. When no one is nearby it would have a constant pitch, and as people move around the object, depending on their distance/movements the pitch would change. Ideally it would drop.

    I did look at PIR sensors, but came to the same conclusion, that it would just be two states that i could achieve. If there was a way to get a proportional signal as you say that would certainly do the trick, but i'm guessing it may be very complicated? I'm definitely a novice here!

    GopherT - Thank you again for your help.

    The solution that you mention with multiple people influencing the tone sounds exactly like what i'm after!

    Could you point me in the direction of the modules you mentioned?

    Thanks all again for your help, it's really appreciated.
     
  13. djsfantasi

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    There are also ultrasonic distance sensors that I am familiar with in robotics. Search for " robotic distance sensor". Trodden Robotics, Robotshop and Sparkfun Electronics are some suppliers. I see two problems. How to change the motor speed and once you know how, how to trigger it with your desired sensor method.
     
  14. foundry

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  15. MrChips

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    You need to take one step at a time.
    The first step is to see how we can vary the tape speed.
    The second step will be the motion/light detection system, finding the right sensitivity and tone modulation.

    You have to decide which of the two Sony Walkman you want to experiment with, FX423 or FX433. The motor and speed controls are quite different.

    The FX423 uses a DC motor. The speed control adjustment is a 470Ω pot in series with a 560Ω fixed resistor.

    The FX433 uses a three-phase stepper motor. The speed control adjustment is a 4.7kΩ pot with 4.7kΩ and 5.6kΩ resistors to form a variable voltage reference.

    You will need a DVM (multimeter) to measure voltage and resistance.

    Here is the location of the RV601 adjustment on FX423:

    [​IMG]



    Here is the location for RV601 for FX433:

    [​IMG]


    The next step is to experiment with a LDR (light dependent resistor).
    Get a hold of various LDRs and measure the resistance in ambient lighting.
    Experiment with each LDR and observe the resistance change as you bring your hand over the LDR. Experiment with a person approaching the LDR and measure the resistance and changes.

    We can adjust the sensitivity at a later stage.

    Do one step at a time.
     
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  16. paulktreg

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    Jun 2, 2008
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    How about varying the supply voltage to the Walkman? Would it be easier? Just an idea.
     
  17. MrChips

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  18. wayneh

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    It might be easier to control the voltage or current to get the desired effect. If the OP has access to a variable voltage power supply, it would be an easy experiment to see what voltage range - if any - gives the desired result.

    Easier isn't always better, though. If the device has a built-in speed adjustment as Mr.Chips is looking at, that is surely a more elegant approach than strangling the power supply.
     
  19. paulktreg

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    I wouldn't call it strangling. You're varying the power supply, say between 2.5V and 3.2V (a little experimentation needed) in response to some sort of proximity sensor.
     
  20. wayneh

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    If your electricity supplier was doing it to your house, maybe you would feel differently. ;)

    My point was that the strategy has limits since other functions will likely fail also as the voltage drops.
     
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