A laser audio transmitter

Here’s a way of transmitting audio that makes it virtually impossible for someone else to listen in. Instead of sending radio waves bouncing all over creation, this uses the focused light of a laser to transmit audio. In the image above you can see the silver cylinder which houses the laser diode. It is focusing the beam on a light dependent resistor to the right which looks almost like a red LED due to the intensity of the light.

The simplicity of this circuit is fascinating. On the receiving end there is no more than the LDR, a 1.5V power source, and a headphone jack. The transmitter is not much more complicated than that. It includes an audio output transformer which boosts the resistance of the audio signal. This increase in resistance ensures that the laser diode modulates enough to affect the LDR on the receiving end. The transmitter uses a 3.3V supply. Check out the video after the break to hear the high quality of audio coming through the setup.

Once you’re done playing around with the transmitter you might try turning the laser into a remote control for your stereo.

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Resurrecting a Hi-Fi cabinet

[VintagePC] pulled this old stereo out of a barn. It was in pretty shabby shape, but he managed get it running again and make it look great as well.

While it had been protected from the elements, it had not been protected from the rodents. Mice had chewed their way through the fiberboard backing and made a nice home inside. He mentions that they chewed the string which operates the tuning dial, and we’re sure they were the cause of other problems as well. He gives the wise advice of not powering on an old set like this until you have a chance to assess the situation.

The insides of the amplifier were about as disorderly as the last radio repair we looked at. But after carefully working his way through the circuits, replacing capacitors and resistors as needed, he started to make some progress. The receiver coil needed to be rewound and he used wire from an old CRT monitor for this purpose. The loop antenna was remounted and the record player arm was given a new cartridge and balanced using a clever LEGO apparatus. Some veneer work and wood finishing brought the case itself back to its original beauty. We’d say the hard work was well worth it. He’s got a big piece of furniture he can always be proud of!

Outdoor stereo helps your neighbors learn to issue noise complaints

Backyard parties are going to rock over at [Effin_dead_again’s] house. That’s because he just finished building this outdoor stereo. It carries its own power supply so you can take it on the road with you, and we don’t think you’ll have trouble hearing it with the 240 Watt amplifier hidden inside.

He shared the equipment details in his Reddit conversation. A 12V lawn mower battery sits in the base of the wooden enclosure. One of the commenters mentioned the dangers of hydrogen off-gassing from that power source, but [Effin_dead_again] thought of that and included venting around the lid. The subwoofer is an 8″ Alpine, and speakers are out of a Hyundai car. The head unit has Bluetooth built in for easy connection to your smart phone. It of course has the ability to play CDs and MP3s too, and we’d bet you can tune the radio if there’s an antenna connected.

Need similar power but a bit more portability? Check out this stereo built into a cooler.

Pimp my scooter

[Glen] built this shiny party machine out of a pretty sad-looking scooter. We’d bet you’re wondering why we think it’s a party machine when it looks so common? The only real giveaway in this photo is the custom exhaust, but hidden in the body of the beast is 720 Watts of party power plus a whole bunch of extras.

When he gets where he’s going, [Glen] parks his ride and lifts up the seat to unfold the entertainment. Attached to the underside of the saddle is a 720 Watt audio amplifier. It drives one big speaker under the seat, as well as two tweeters and two mid-range speakers that were fitted into the front console. But these days a party isn’t a party without some video, and that’s why you’ll also find a 7-inch LCD screen suspended from the upright seat. Tunes and videos are supplied by an iPod touch up front, or the PC he built into the ride. All it’s missing is a gaming console!

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Fifty dollars to make your car audio Bluetooth compatible

We’re rather impressed with the work [Aaron] did to add Bluetooth connectivity to his 2008 Honda. He used an aftermarket kit, but rolled in his own revisions to make it look and feel like an original feature.

After being disappointed by an expensive docking system he grabbed a Jensen BT360 kit for about $35. It comes with an external speaker which would look horrid mounted on the dash. That speaker is meant to play your telephone audio via Bluetooth, while music from the phone is sent to the car stereo using an FM transmitter. Since he planned on hiding the control unit under the dash anyway, it wasn’t too hard to add some wires which intercept the audio being fed to that FM transmitter. From there he added a couple of relays to automatically route the audio signals (when present) and patched the whole thing into the Aux input. This way he doesn’t need the extra speaker, and all sound is feed to the head unit via wire instead of radio transmissions.

The final setup works pretty well. If a phone call comes in it automatically mutes the volume, or pauses the iPod if that’s what’s currently playing through the Aux port. [Aaron] thinks the bass from music played via Bluetooth is not quite as rich as when using the Aux port, but if you don’t mind the cables that’s still an option too.

Hard resetting your Ford Touch system the easy way

ford-sync-reset

[Jeff Clymer] owns a Ford Focus, and while he’s generally happy with the car, the “My Ford Touch/Sync” system can be buggy at times. He spends a lot of time in the car each day, so when the entertainment center locks up as it is frequently known to do, he has to turn off the car and pull a fuse to reset the system. Since pulling a fuse while on the road is pretty impractical, he decided to install a reset button, making system reboots a breeze.

He started by disassembling various fuses until he found one with an easy to remove fusible link. Once it was in pieces, he soldered a pair of wires to the fuse terminals and connected everything to a normally closed momentary pushbutton switch. After adding an inline fuse holder and reinserting the original fuse, he installed the button into the back of his glove box

Now instead of physically removing the fuse each time his stereo locks up, he can simply push a button and be on his way. Here’s hoping a software fix is coming for [Jeff’s] car sooner rather than later!

Improving terrible computer speakers

[Victor] likes to watch movies on his laptop, but the tiny speakers in his machine don’t do [John Williams] and other perfectly fine soundtracks justice. To pump up the jams a little bit, [Victor] got a pair of Trust Mila 2.0 speakers for Sinterklaas. Unfortunately, these speakers were terrible – noise everywhere, tinny output and a brighter-than-the-sun blue LED. These problems were fixed once [Victor] replaced the amplifier in both speakers.

After shopping around for a new power amp to go in each speaker, [Vic] hit upon the MAX9575 3.2 Watt amplifier. This little guy met all of [Victor]’s requirements. The only problem is that the MAX9575 is only available in a TQFN package.

After a deep breath and much sweat of the brow, both amps found a new home in their respective speakers, deadbug style. It probably would have been easier to etch a PCB, but we’ll give a tip of the hat to [Victor]’s fine motor skills anyway.

Because of the insane soldering skill demonstrated in the title pic, [Vic] now has a really nice pair of speakers. Check out the demo of the improved speakers after the break.

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