Post by thread:[OT]: PDA Case Passthrough

I recently aquired a Heavy Armor (http://www.armorbyotter.com) case for my PDA. It is a waterproof, crushproof, airtight case that still allows use of the PDA. It's really fantastic, it's even large enough for me to leave my compact flash 802.11 card in the unit, so I can use wireless while still environmentally protected. Sweet. However, there is one downside. When I wish to listen to some MP3s, I have to take the unit out of the case. So, I was trying to think of a way to get stereo audio out of the case without completely compromising the integrity of the case. Here are a few of my ideas: 1) Mechanical - If I could come up with a watertight connector, that might be an option. A watertight 1/8" stereo jack would be really cool, but I don't know if such a beast exists. Anyone seen anything relatively small (ie not mains plug sized) like this? 2) Optical - The bottom of the case is clear, so I was thinking about multiplexing the stereo signal into one stream and transmitting it optically through the case. This could work. I would have to make the internal portion of the circuit rather power efficient because I can't put D cells in there to power it. I was thinking of multiplexing into one signal because I was worried that if I transmitted two signals, I'd get some interchannel interference as the light travels within the polycarbonate. 3) RF - This shouldn't be too hard. There must be thousands of little FM transmitters online. I would get one of those small cheap autoscan radios to receive the signal. Again, I don't know how power efficient those little transmitters are. 4) Induction - This one is perhaps a bit more wacky. I was thinking that with a couple of coils on the inside, and two more on the outside, I could pass the audio inductively between the two. Is this even feasible? An ideal solution would be bluetooth of course. Though I have yet to see a bluetooth stereo headphone, and no doubt it would be out of my price range. If only there was an 802.11 headset :) Ideas, suggestions, threats, all welcome :) Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> 3) RF - This shouldn't be too hard. There must be thousands > of little FM transmitters online. I would get one of those small > cheap autoscan radios to receive the signal. Again, I don't > know how power efficient those little transmitters are. Have a look at the Rohm BH1417F (183kB) http://www.rohm.com/products/databook/audio/pdf/bh1417f.pdf ================================================ You could probably make a TX with lower power consumption from discrete components eg Harry Lythall's transmitters work OK http://hem.passagen.se/sm0vpo/right.htm There are a few simple mono transmitter/bug kits & circuits around that use little power, but I'm not sure how you'd make a stereo version out of them with the two channels on the same frequency -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Thursday 06 February 2003 08:43 pm, you wrote: > I recently aquired a Heavy Armor (http://www.armorbyotter.com) case for my > PDA. It is a waterproof, crushproof, airtight case that still allows > use of the PDA. It's really fantastic, it's even large enough for me > to leave my compact flash 802.11 card in the unit, so I can use > wireless while still environmentally protected. Sweet. However, there > is one downside. When I wish to listen to some MP3s, I have to take > the unit out of the case. So, I was trying to think of a way to get > stereo audio out of the case without completely compromising the > integrity of the case. Here are a few of my ideas: > 1) Mechanical - If I could come up with a watertight connector, that > might be an option. A watertight 1/8" stereo jack would be really > cool, but I don't know if such a beast exists. Anyone seen anything > relatively small (ie not mains plug sized) like this? Hard to guarantee no leaks on any "normal" audio jack. Maybe a bnc or tnc connector would work better. > 2) Optical - The bottom of the case is clear, so I was thinking about > multiplexing the stereo signal into one stream and transmitting it > optically through the case. This could work. I would have to make the > internal portion of the circuit rather power efficient because I > can't put D cells in there to power it. I was thinking of > multiplexing into one signal because I was worried that if I > transmitted two signals, I'd get some interchannel interference as > the light travels within the polycarbonate. This should be workable, but probably not without issues outdoors. > 3) RF - This shouldn't be too hard. There must be thousands of little > FM transmitters online. I would get one of those small cheap autoscan > radios to receive the signal. Again, I don't know how power efficient > those little transmitters are. > 4) Induction - This one is perhaps a bit more wacky. I was thinking > that with a couple of coils on the inside, and two more on the > outside, I could pass the audio inductively between the two. Is this > even feasible? Absolutely, this could work. > An ideal solution would be bluetooth of course. Though I have yet to > see a bluetooth stereo headphone, and no doubt it would be out of my > price range. If only there was an 802.11 headset :) > > Ideas, suggestions, threats, all welcome :) I saw a really cool star trek looking earpiece complete with a short microphone for cell phones that (apparantly) used bluetooth. Just caught the tail end of the review, but the reviewer really liked it, that's for sure. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Thanks all for the suggestions so far. The LEMO connectors look good, however after looking at them I don't think they will fit my application. The problem is the case is very curvy, and the only flat place to put a connector would be right on the back. This would present a big stickout when the external cable is mated to it, and the unit wouldn't sit properly in my pocket. Plus the LEMO website is kind of annoying :) I was thinking more about the induction idea. Here is my theory, go ahead and shoot it down :) I was thinking that since the PDA is already set up to output to drive headphones, induction might not be too hard to implement, possibly with no active parts inside the case. If there was a way to put two coils on the inside and have them driven from the headphone outputs of the PDA, then in theory the magnetic field should be able to be picked up from the exterior of the case right? Question is, will I be able to keep the two channels from having their magnetic fields interact horribly? Plus, I have absolutely no idea how to pick up the signal on the outside. Any suggestions? I looked at some of the FM transmitter circuits on the net. I'm worried that I either won't be able to find the specialty components needed, or that I won't be able to fit them into the case. I am going to look around for some of the commercial products and see if I can hack them up. Thanks all :) Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams "Alan B. Pearce" wrote: > I would use a connector from Lemo. These are pricey, but do come in > watertight versions suitable for medical and other uses that require tight > seals. get a 4 pin (you may find a 3 pin) and have an external Lemo to jack > lead. If you use a suitable size connector you may be able to build a jack > into the back of it. > > See http://www.lemo.com/ for a website that is a bit funky to use (wish you > could turn off the "chunk" noise). -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

If you use induction, it seems that the best way to pick up the signal would be with another set of coils. To combat interference between the two signals, I suppose you could mount the two coils on opposite sides of the case, then have a coil on the outside right next to each inside coil. Of course, doing this would necessitate running a bit of wire between the headphone output and the coils. If you don't really want stereo, I think putting the coils next to each other would probably just give you mono sound, but in that case you'd be better off just using one coil. There may be other methods that are much better for doing this that I don't know about, but this is the one that comes to mind for me. Daniel Imfeld {Original Message removed}

Maybe I'm underestimating induction here, but won't that yield in SIGNIFICANT quality loss in sound? Does this not matter? It just seems like it would be used in a lot more applications if it were a fesable solution to this type of problem. Maybe I just haven't seen enough... Quoting Daniel Imfeld <spam_OUTdimfeldTakeThisOuTSOFTHOME.NET>: {Quote hidden}> If you use induction, it seems that the best way to pick up the signal would > be with another set of coils. To combat interference between the two > signals, I suppose you could mount the two coils on opposite sides of the > case, then have a coil on the outside right next to each inside coil. Of > course, doing this would necessitate running a bit of wire between the > headphone output and the coils. If you don't really want stereo, I think > putting the coils next to each other would probably just give you mono > sound, but in that case you'd be better off just using one coil. There may > be other methods that are much better for doing this that I don't know > about, but this is the one that comes to mind for me. > > Daniel Imfeld > > {Original Message removed}

I looked on Google a bit, and it seems that audio induction is used in many places for people with hearing aids, especially in England. The amplifier is hooked into an induction loop, and a coil in the person's hearing aid will pick up the speaker's words. I don't know if it's feasible to do this with a PDA though, as many of these sites say you should have an amplifier that can put out a few hundred watts. Also, there does seem to be some signal degradation even with just speech, so I imagine that for music the degradation would be much more noticeable. Here's a few links I found with some more info. www.epanorama.net/documents/audio/induction_loop.html www.cunnings.co.uk/product/inductionloops/ http://www.applesound.co.uk/help/faq_afils.htm http://www.ibs.org.uk/archive/iloops0005.html Searching for audio induction on Google turns up a number of other links too. Daniel Imfeld {Original Message removed}

> Plus, I have > absolutely no idea how to pick up the signal on the outside. Any > suggestions? A telephone pickup coil? Radio Shack used to sell these to record phone calls, I don't know if they still do though. Probably not, as it doesn't pertain to computers or TV. ;-) At any rate, you should be able to find one somewhere. They are a pickup coil that has a built in suction cup to stick it to the handset. They seem to be fairly sensitive since they picked up the conversation inductively from over 1" from the ear piece. michael -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hi, Best signal at minimal cost will be a direct connection. How waterproof do you need? Can you use a panel mount 1/8" stereo jack and glop up the back side with silicone RTV? Maybe cover it with a little vinyl cap if you don't like the looks. Wouldn't be dive worthy but could certainly be rainproof. Dave Josh Koffman wrote: > 1) Mechanical - If I could come up with a watertight connector, that > might be an option. A watertight 1/8" stereo jack would be really cool, > but I don't know if such a beast exists. Anyone seen anything relatively > small (ie not mains plug sized) like this? -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Thank you everyone for the ideas. I think Bob's idea (listed below) is one of the best. Once I realized that because of the curve of the case, mounting a panel mount jack would result in having to place it in an akward position, I started looking elsewhere. I still like the induction idea, basically I'd be making two air/plastic core transformers. I'd be a bit worried about the sound quality, plus I probably couldn't use my original idea on how to affix anything external to the case -- magnets :) At the moment I'm focussing building a small FM transmitter into the case. This will be a bit of work, as I'll need to fit in a bettery pack, and some sort of externally triggerable power switch. However, there is one huge benifit...when I am in a car, I can just transmit MP3s to the car radio as well. In addition, it won't require any modification to the case itself, so I can always remove it. Anyway, I will keep you all posted on how it goes! Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams Bob Ammerman wrote: > How about three small brass bolts mounted thru the case with rubber washers. > Now you build a strap/case/cradle that wraps around and makes contact with > the three bolt heads. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 08:43 PM 2/6/03 -0600, Josh Koffman wrote: >I recently aquired a Heavy Armor (http://www.armorbyotter.com) case for my PDA. >It is a waterproof, crushproof, airtight case that still allows use of >the PDA. It's really fantastic, it's even large enough for me to leave >my compact flash 802.11 card in the unit, so I can use wireless while >still environmentally protected. Sweet. However, there is one downside. >When I wish to listen to some MP3s, I have to take the unit out of the >case. So, I was trying to think of a way to get stereo audio out of the >case without completely compromising the integrity of the case. Here are >a few of my ideas: Have a look at how they get audio from something like a MP3 player into an automotive cassette player. Its a cassette shell with a spring loaded tape head that touches the tape head in the cassette player. Audio quality is surprisingly good and is stereo. My thought was to remove the head from one of those adapters and cut a hole through the case that just fits the head. The head itself is a solid block of metal and epoxy and is quite waterproof. You should be able to seal it to the case quite easily. The head is driven directly from the headphone out of your MP3 player - just use the cable that came with the adapter. The receive end is a bit more complex but not too bad. I'd start with an old portable Walkman type cassette player and gut it for the playback electronics and tape head. Some of those units (the better ones) are actually fairly quiet and should work OK. The nice thing about this is that most of the bits and pieces already exist - all you have to do is arrange them to work for you. dwayne -- Dwayne Reid <.....dwaynerKILLspam@spam@planet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 18 years of Engineering Innovation (1984 - 2002) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

On Sat, 8 Feb 2003, William Chops Westfield wrote: *>Shouldn't it be pretty easy to feed CONDUCTORS through a case in a *>watertight manner? Mount your connector outside, and who cares whether *>the connector is watertight... Anybody who did this will tell you it is not simple. The conductor, the glue, and the fixture work against each other and there is always some leakage. Totally waterproof passthroughs are very hard to make without some hi-tech materials and some machining. Otoh if you just want to keep the rain out, go for it. Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.