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TD7297 amps are known to get really hot. I was concerned the impedance of the motors was too low when I first started testing but then found online that this is common https://www.google.com/search?q=tda7297+hot though I can't imagine installing one in a sealed cabinet as many do to make a portable bluetooth speaker. They are also supposed to have a thermal protection switch but I never tripped it during my testing
The only thing I can tell you is to make sure you use those uxcell 5000 RPM 6V High Torque motors I linked to in the parts list. I ordered motors from several different sellers on both Amazon and eBay and those were the only ones that had enough torque to maintain good control of the mirrors. Others I tried that looked identical with the same exact housing were too weak and made the pattern too loose and bouncy. Also, if you order those cheap amps from China make sure you order more than one because a full third of the ones I received were DOA or the potentiometers were cracked since they ship them in a plastic envelope, not boxed.
It doesn't matter which side goes where because when the ignition is turned on and closes the relay, all it is doing is providing continuity between the blue wire (30) and the yellow wire (87). These relays are normally used to provide 12V power to an accessory such as fog lights or an LED light bar. In that case the blue wire (30) is usually also connected to the 12V source and when the relay is activated it passes the 12V current on to the the yellow wire (87) which is connected to the accessory. In this case, however, all we are simply doing is passing the peach wire's signal from the the blue wire (30) to the yellow wire (87) to complete it's path.
I didn't like that crude schematic so I wired everything up today (outside of the box) and took a picture of it for you. Please note that those power wires are shortened greatly before installation.
I finally had some time today to sit down to add more details and links to all of the parts.
Head in a Jar Prank
Laser Box Music Laser Light Show
I didn't realize those could take an analog signal. I was seriously going to go that route then came upon the idea of using inexpensive motors and discovered they fit inside the conduit fittings and then fell in love with the industrial look of the electrical box. Good thing I didn't know any better :)
Hard to go wrong with Pink Floyd ;)
You get it. I was just trying to gauge interest. It costs more than $50 in parts and accessories to build each one. I will have to raise the price if I decide to make any more in the future.
Thank you. I added a precaution to my last laser project but frankly forgot to do so with this one. I'll go back and add that info.
Yes you can do that by applying separate EQ settings to each laser box but for the purposes of the demo videos I was trying to show that the patterns are not some random bouncing of a mirror; Each song has it's own unique, repeatable pattern. All the boxes produced relatively the same pattern even though they were not synchronized in any way other than sharing the same audio signal.
Where were you last month? I was racking my brain trying to figure out how to cool the diode while keeping it isolated before landed on the diode route. You know how expensive thermally conductive but electrically nonconductive tape is? lol
Yes I looked at http://www.ebay.com/itm/252300684989 but in the end decided to keep it all analog to make it as simple and compact as possible. Since this this involves no programming, it's more pure or even organic in a way. You "see" the music, not someone's programmed patterns.
Thank you. It could be done but you would have to install multiple lasers and prisms but that would greatly add to the size and complexity.
I couldn't find an amp with a built in EQ small enough to fit inside the box but it could be applied to the input signal.
I saw your wonderful comments. Thank you!
Thank you. I'll draw something up and add it to the instructable.
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No, the parking lights will not work with the ignition off the way I have it wired.
Thanks! Cars are getting more complicated with the computers and electronics for sure. I found this relay that has an adjustable delay that could keep the headlights on for up to three minutes after the ignition is turned off. It fits a standard 12v automobile relay harness so it is plug and play. http://www.qualitymobilevideo.com/bu508td.html
OMG! I watch those guys all the time on Youtube but I swear I have never seen that episode! I'm glad I didn't or else I wouldn't have figured out how to do it with only one relay without cutting any high power wires to the headlights.
I thought about that and I guess I could wire two relays both in parallel for redundancy but there are many relays in a car and any one of them could fail at any time. I agree none are as critical as the one for your headlights so I did tell my son that if his headlights go off while driving he should pull back on the stalk (for flashing your headlights) and hold it until he can pull over safely.
It would 99 times out of a 100 but just in case he forgot that one time... And I probably did it more for his convenience more than anything else. Turning off your headlights is so 80's :)
Thank you! I've noticed the ends of the wires corrode very quickly so I have to pull it down a quarter inch every month or so and snip off the ends. Luckily I have 20 extra feet coiled up in the attic! Also I've discovered I don't even have to strip the wires, just cut it. The water contacts with the copper inside the insulation just fine which is great so I don't have to worry about any wire slivers getting into their water.
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