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You can explain to a child that listening to music at a high volume can cause hearing loss, but that doesn’t mean they will listen. Then again, you could make this neat little device and make them use it. The only problem? How do you get them to keep it plugged in? – Link

Marc de Vinck

I’m currently working full time as the Dexter F. Baker Professor of Practice in Creativity in the Masters of Engineering in Technical Entrepreneurship Program at Lehigh University. I’m also an avid product designer, kit maker, author, father, tinkerer, and member of the MAKE Technical Advisory board.


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Comments

  1. John Laur says:

    To make them keep it plugged in you’ve gotta make it the only way they can plug in the headphones. Either cut the end off the headphone plug and build it directly into them or change the type of plug so that the volume limiter device becomes the only possible adaptor to attach them to the device. What? You have two pairs of headphones? Simple; switch the jack in the device to something only the volume limiter can plug into — if you don’t mind voiding warranties anyway.

  2. Jack says:

    Superglue, or whack the little darling upside the head and get them to mind you.

  3. DF says:

    That page is more proof that explanations of even the simplest projects can benefit from a properly drawn schematic. Trying to describe a voltage divider to someone by mentioning a “couple” resistors – when half (or more) of the audience is likely to never have even heard of Ohm’s Law – seems like a waste of effort.

  4. Mike says:

    @DF

    It is (2) resistors, that’s it. 1 for each wire of the headphones.

    “use two 10 Ohms resistors”

    Go to Radioshack and ask for them….nothing about voltage dividers, nothing about ohm’s law. You can do it.

  5. jeff says:

    or you could always build it into their Daisy mp3 player :P

  6. Simon says:

    Mike, I don’t think DF is confused. He is just saying for people who don’t know much about electronics a simple diagram would help. The project description is just plain confusing:

    “I chose to use two 10 Ohms resistors for each channel since I figured that the headphone impedance would be around 16 Ohms at DC. I did not use one 22 Ohms resistor since I thought 10 Ohms per channel would be enough but found out that it wasn’t, so I added another 10 Ohms resistor on each channel.”

    I have read that multiple times and still don’t know what he’s on about! He talks about resistors in series with each channel then mentions two resistors per channel and talks about voltage dividers. To me a voltage divider would mean he has the two 10R resistors in series across the input of each channel and then taps off from between them to feed the headphone output. But then it seems he just means you have 20R of resistance in series with each channel?

    A simple drawing would help. Should also mention you should make sure you don’t get your left and right channels swapped!

  7. Carlitos says:

    Hello,
    I’m aware that the explanation was very cryptic and horribly written. I updated the post so I think now it should be clearer.

    (Note that I tried to correct this post before but for some reason, the changes I made were not saved.)

    BTW, I’m not making a diagram for this circuit since it is too simple and a not so clever design.

    Cheers

  8. DF says:

    @Simon:

    You are correct. He didn’t build a voltage divider. A voltage divider is different than adding a series resistance. I suppose one could say he is using the load (the driver from the headphone) as the second resistor in the divider network, but that’s not what the description said. Does it work? Sure, increasing the impedance seen by the headphone output of the MP3/walkman will reduce the volume because small players just don’t have the ability to drive high impedance headphones. It’s why everyone with a high quality, high impedance set of cans goes out and build “mint” tin headphone amps – to get added volume, clarity, and better bass from an opamp circuit with a low impedance output.

    The other problem I see is that this is only going to reinforce the idea that the volume control must be maxed out (or nearly so) in order to listen to music at a level which the child enjoys. You’re not really changing the behavior, just masking its effects.

    BTW, MAKE: this new captcha sucks.

  9. rbarris says:

    for those who have kids listening to iPods, take note of the volume limiting feature, you can tell the iPod to stay below a certain level and lock it with a PIN number.