DC power generation from cassette

[Pandamonium]

It's been a (long) while since I had E&M, and I figured someone here would know. Okay so I'm wondering if it's possible to generate enough voltage from the motors powering a cassette player to fully power USB devices.

Here's the big picture. My car has a CD/Cassette deck, and I pretty much need a GPS to avoid getting lost. I live in a high crime city, so I don't like the suction cup mounts. I'd like to attach my GPS mount to a cassette and stick it in the cassette deck (it's been done before). Then I remembered that I don't have aux-in, and how cassette adapters are pretty much my best option for playing music from my ipod. So I'd like to combine this into one device. That's not a problem at all- I'm pretty sure it would work. But then I thought about all the wires....

I'd have a power cable going to the GPS, a power cable going to the iPod, and a twisty-tied cable going from the cassette to the ipod... not really ideal in my opinion... I'm a minimalist kind of guy.

I'm in the market for a new GPS, and I've got my eye on the Nuvi 265WT. It only has a mini USB connector, so I imagine it's limited to 5V/1.8A. I also imagine the iPod is limited to the USB spec. (From wiki, it seems like official current draw is maxed out at 900mA, but for dedicated charging with no communication, overdraw to 1.8A is allowed per powered USB port.) I also googled DIY cassette adapters. Apparently all it involves is coiling a 30 Ga wire near where the tape would be read to act as an inductor. (http://www.streettech.com/archives_DIY/audioAdapter.html)

That leaves a bunch of space around the spindles to try to generate power. Apparently someone thought of it already because there's a patent on it (http://www.freepatentsonline.com/6307274.html), but I'm willing to infringe on this one if it could theoretically work. So ideally I'd like enough power generated to power two USB port equivalents electrically with the voltage/current "sense" line intact. I think this might involve a USB controller, but I'm not sure. Anyway, it's a lot to ask, but technology is pretty awesome. So does anyone know where to start?

By the way, wiki reports that cassette heads move the tape at 4.76 cm/s. I don't know the radii of the gear things though.

To make this even more complex (and kind of awesome), if there were room for circuitry to detect changes in cassette head angular velocity (but not alter power output to USB) and take those signals and output next/previous on an iPod, that would be pretty sweet. It'd be a dual device powered cradle with zero wires. God I'm a dork.

 

[canis]

It's been a (long) while since I had E&M, and I figured someone here would know. Okay so I'm wondering if it's possible to generate enough voltage from the motors powering a cassette player to fully power USB devices.

Here's the big picture. My car has a CD/Cassette deck, and I pretty much need a GPS to avoid getting lost. I live in a high crime city, so I don't like the suction cup mounts. I'd like to attach my GPS mount to a cassette and stick it in the cassette deck (it's been done before). Then I remembered that I don't have aux-in, and how cassette adapters are pretty much my best option for playing music from my ipod. So I'd like to combine this into one device. That's not a problem at all- I'm pretty sure it would work. But then I thought about all the wires....

I'd have a power cable going to the GPS, a power cable going to the iPod, and a twisty-tied cable going from the cassette to the ipod... not really ideal in my opinion... I'm a minimalist kind of guy.

I'm in the market for a new GPS, and I've got my eye on the Nuvi 265WT. It only has a mini USB connector, so I imagine it's limited to 5V/1.8A. I also imagine the iPod is limited to the USB spec. (From wiki, it seems like official current draw is maxed out at 900mA, but for dedicated charging with no communication, overdraw to 1.8A is allowed per powered USB port.) I also googled DIY cassette adapters. Apparently all it involves is coiling a 30 Ga wire near where the tape would be read to act as an inductor. (http://www.streettech.com/archives_DIY/audioAdapter.html)

That leaves a bunch of space around the spindles to try to generate power. Apparently someone thought of it already because there's a patent on it (http://www.freepatentsonline.com/6307274.html), but I'm willing to infringe on this one if it could theoretically work. So ideally I'd like enough power generated to power two USB port equivalents electrically with the voltage/current "sense" line intact. I think this might involve a USB controller, but I'm not sure. Anyway, it's a lot to ask, but technology is pretty awesome. So does anyone know where to start?

By the way, wiki reports that cassette heads move the tape at 4.76 cm/s. I don't know the radii of the gear things though.

To make this even more complex (and kind of awesome), if there were room for circuitry to detect changes in cassette head angular velocity (but not alter power output to USB) and take those signals and output next/previous on an iPod, that would be pretty sweet. It'd be a dual device powered cradle with zero wires. God I'm a dork.

Power output is nowhere near what is needed to run the GPS unit. You would have difficulty lighting a led with a mechanically reasonable electric generator inside cassette.

"and take those signals and output next/previous on an iPod"
That can be done easily provided the electric generator mechanism is built inside cassette case.

I suggest using the cigarette lighter as mount and power source. The cassette idea is unnecessarily complicated.

 

[PottedMeat]

Take apart any old cassette deck and look at the motors - they're not rated for anything more than ~12V@~50-100mA.

So you want to take 5V@1.8A = 9W @100% efficiency from something that can output maybe 1.2W max?

 

[Modelworks]

As said you would have to create more power than you put into it, the only thing able to do that is nuclear/plasma generators. Don't think they will fit in a cassette adapter

The best way to handle this is to replace your car radio with one that has the inputs that you need. You can get a radio with what you need for $20 almost anywhere. If you can build a device like you are asking about then you can definitely install a car radio.

 

[Rubycon]

Neat concept but as previously mentioned the motor working as a generator would not get anywhere near that power.

Perhaps a few hours on fast forward may be able to charge a battery but it would be a long drive.

 

[Pandamonium]

Damn. Well so much for that idea. If it were possible, I'd be all over that solution. I thought about going aftermarket, but I really like the OEM look. Plus the lack of a security system makes me wary of having anything aftermarket in plain sight. My old car got broken into for a simple 1CD stereo. I had glass coverage so it didn't cost me anything but I had to drive around for 2 days with a broken rear triangle mirror, and the rain pissed me off to no end.

The other thing is, if I'm going to start modifying my car, my eye starts to drift towards Car PCs with touchscreens and the whole shebang. It's totally not what I should be looking into for a ~8yr old car.

 

[Colt45]

On what planet is USB 5V 1.8A?

Last I checked, it's 500mA max. 100mA for most things.

 

[DominionSeraph]

No. Even if the motor were powerful enough, the resistance would trip auto-reverse.

 

[bobdole369]

God I'm a dork.

Then you should take the radio apart and latch onto the 12V inside, build you a 5V switching supply and be done with it! They make 1A regulators from 12V in - Would easily fit inside a cassette tape.

 

[nedfunnell]

Then you should take the radio apart and latch onto the 12V inside, build you a 5V switching supply and be done with it! They make 1A regulators from 12V in - Would easily fit inside a cassette tape.

I vote for this route also. To power two USB devices at the 500mA spec, you'd need 5W, which you aren't going to get either from the reading head or the motor(s). Sorry.

I vote for taking the sucker apart and somehow making the 12v available to the cassette- some brushes and contacts, a properly-situated plug, etc. Then it's just a matter of running it through a LM7805 (I'd get the TO-3 package rather than TO-220, or a TO-220 for each device would be save) to give you your 5V.

 

[NeoPTLD]

Garmin GPS doesn't follow USB rules. The OEM power cable allows 1A draw, but it has a resistor between sense and ground so that it knows its connected to Garmin power cord rather than USB port.

If you're using non-OEM cord, it assumes USB and only allows 500mA draw and won't charge and operate at the same time.

I'd look into mounting a magnetic holder on dash that physically holds the GPS as well as power connection by spring loaded contacts (like the cord-trip safe connector used on Mac laptops) Get the power to cradle by tapping into the back side of cig lighter socket.

 

[0roo0roo]

cassettes used to jam so much.
the motors were weak, as to not shred the tape to bits.

 

[victorm]

local shop here has a cig lighter charger that gives ipaq/nokia/ipod/usb options with a set of adapters. why not just mount the gps on the cassette adapter (if you can use if in that position, that is) and power it neatly this way? you don't need it all the time and you can assemble the whole thing under 30s while driving if running out of battery.
your idea is interesting, but hardly reliable imho.