Im working on a burning man project, and need to build or find an 8 way switch that can distribute a single input, at speaker power level, to 8 different speaker outputs, one at a time in sequence with a user adjustable speed (~0 - 1200 Hz?). I've already come up with a mechanical switching system, using a 12v cooling fan motor speed adjusted by a rheostat that turns and sequentially triggers an array of momentary micro-switches. However, I think the mechanical "clicking" and the interference noise that's generated by the switches is going to be way too loud. Oh yeah, the whole thing has to run off a 12v power source, that is, a deep cycle marine battery (90 amp hours), so Im looking to minimize power consumption so the contraption will run for a while without sucking my battery dry. The cooling fans use almost .6 amps apiece. Hope there's a better alternative. Ultimately I want there to be two of these switching systems in parallel sending their output to the same set of 8 speakers, but be independantly adjustable (so we can play with the harmonic crazyness, especially if the second switcher is reversed and going the opposite way) Does anyone have any ideas? I've been trying to puzzle this one out for a while. Im not an electrical engineer, more of an electrical hacker... but I can learn!!! I hope to find the most simple, and durable design possible. Thanks!
Hi, I may be useful to back up a step or two here and explain just what this whole thing is supposed to do. That may lead to a more usable solution.
Hi, Sure, This is meant essentially to be an audio toy for the Burning Man festival. The idea I'm shooting for here is this: 8 speakers in a circle, about 10 feet equidistant from a central point, facing inwards, towards the user at the center with the controls. At the central controls would be a system of distributing an audio signal to the circular speaker array in a sequential, rotating, adjustable speed manner. Ideally, I would like two distinct audio signals to be available, one spinnging in one direction, the second spinning in the other direction (or possibly reversable directions too). Through one audio channel would be an ambiance musical collection of random stuff off an MP3 player. On the other audio channel would be the output of a collection of a bunch of sound generating nick-nacks and junky kids toys, messed-up casio pianos, etc... that would be available to play with and make noise. The speed of the spinning audio channels would also be adjustable from close to 0 cycles/second (hz) to some upper limit towards where it no longer sounds like distinct individual speakers (unknown speed as of yet, Im guessing something like 30 - 60 Hz. In addition, I want the whole thing to be triggered on only when someone walks up to it and engages it, otherwise it would continue to drain the battery while no one is around... it needs to last a few days in the desert before a recharge. Was thinking of some kind of power relay triggered by a switch in a small foot panel thing when the user steps up to use the controls, like maybe a bathroom scale. That would turn on a couple of small 12v lights, or possibly LED light arrays to illuminate the controls at night. When idle, the contraption would have a blinking stobe on top to attract attention and keep people from riding their bike into it in the dark. So far I envisioned using a mechanical switching system with the afore mentioned cooling fan motors speed adjusted by a rheostat (still rotate too fast I think even close to stall speed ~4.5v) triggering an array of small momentary reed switchs (which I think are too electrically noisy). These switches would distribute a speaker level signal from a single amplifier to the eight speakers, with the left channel going clockwise, and the right channel going counterclockwise. From what people have been telling me on online forums, a solid state IC approach switching line level signals, distributed to 8 discrete amps would be better. I also have an assortment of other 12v appliances, such as a car alarm siren, a 12v black light, and some other assorted lights and junk, including the cooling fans, and relays, etc.. Hope that helps make sense of the project goals..... thanks again for any advice you guys might have! -Gabe
Hi, Sure, This is meant essentially to be an audio toy for the Burning Man festival. The idea I'm shooting for here is this: 8 speakers in a circle, about 10 feet equidistant from a central point, facing inwards, towards the user at the center with the controls. At the central controls would be a system of distributing an audio signal to the circular speaker array in a sequential, rotating, adjustable speed manner. Ideally, I would like two distinct audio signals to be available, one spinnging in one direction, the second spinning in the other direction (or possibly reversable directions too). Through one audio channel would be an ambiance musical collection of random stuff off an MP3 player. On the other audio channel would be the output of a collection of a bunch of sound generating nick-nacks and junky kids toys, messed-up casio pianos, etc... that would be available to play with and make noise. The speed of the spinning audio channels would also be adjustable from close to 0 cycles/second (hz) to some upper limit towards where it no longer sounds like distinct individual speakers (unknown speed as of yet, Im guessing something like 30 - 60 Hz. In addition, I want the whole thing to be triggered on only when someone walks up to it and engages it, otherwise it would continue to drain the battery while no one is around... it needs to last a few days in the desert before a recharge. Was thinking of some kind of power relay triggered by a switch in a small foot panel thing when the user steps up to use the controls, like maybe a bathroom scale. That would turn on a couple of small 12v lights, or possibly LED light arrays to illuminate the controls at night. When idle, the contraption would have a blinking stobe on top to attract attention and keep people from riding their bike into it in the dark. So far I envisioned using a mechanical switching system with the afore mentioned cooling fan motors speed adjusted by a rheostat (still rotate too fast I think even close to stall speed ~4.5v) triggering an array of small momentary reed switchs (which I think are too electrically noisy). These switches would distribute a speaker level signal from a single amplifier to the eight speakers, with the left channel going clockwise, and the right channel going counterclockwise. From what people have been telling me on online forums, a solid state IC approach switching line level signals, distributed to 8 discrete amps would be better. I also have an assortment of other 12v appliances, such as a car alarm siren, a 12v black light, and some other assorted lights and junk, including the cooling fans, and relays, etc.. Hope that helps make sense of the project goals..... thanks again for any advice you guys might have! -Gabe
Just a thought (or maybe a complication If you fade (as opposed to hard switch) between speakers, you could do it with four, 90 degrees apart. -- John Miller Email address: domain, n4vu.com; username, jsm Surplus (FSoT): F. Besson International (800) trumpet, Bb, silver New Conn V1 double trumpet case, no logo Tektronix 465B oscilloscope
Hi Gabe, I have to agree, but I think you would need to fade out during the shift, to avoid cliks and pops anyway. If you use two analog multiplexers (as they are called), one can control the music and the other the sound fx - with variable speed clocked up/down counters to control each, you can pretty much get the sound patterns you care for. -- Regards, Soeren * If it puzzles you dear... Reverse engineer * New forum: <URL:http://www.ElektronikTeknolog.dk/cgi-bin/SPEED/>
The clicking is going to be present with electronic switches as well, simply due to the dicontinuities in the waveform. You will need to fade in and out to avoid that, which means you are probably better off doing it at low levels and using separate power amps for each channel. Fader mechanisms are many and varied. You can use incandescent lights and CDS photocells for a fairly simple system, with the internal time constants of the bulbs and photocells providing the fades, possibly with an RC added to the bulb drivers. (In which case you could use LEDs instead.) The CDS cells are slow-responding variable resistance, so just use them in voltage dividers to the various amp inputs. As usual, you can get a *lot* more sophisticated if you feel the need. Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis www.daqarta.com
One way to do this which might not be too expensive would be to use digital potentiometers. The dallas DS1866 is a digital pot which has a 3 pin parallel control input, yielding 8 possible settings of the pot. Using some kind of counter circuit, you could program the settings for these, and use their outputs as inputs to your 8 separate power amps. To do two channels rotating in different directions, you would have to have two sets (meaning 16 of these DS1866s,) each pair of which would be followed by a circuit to add the outputs. Then, the final output would be the input to the power amplifier for that speaker. The digital logic design is a bit hairy, I think. You would have to present the control pins on the different digital pots with a control stream looking like ...,0,0,0,0,1,2,3,4,5,6,7,6,5,4,3,2,1,0,0,0,0,... to bring up and fade out the volume. The same control stream would go to the other speaker controls, timeshifted for the rotational effect. The 8 different levels might cause pops on the speakers when they were changed, I don't know. There are digital pots which have more settings, but you would have to program them with a microcontroller using some kind of 3 pin interface. Actually, that's probably the easiest way to do this; use a set of maxim DS1801s to roll the volume signal through a set of 8 cascaded digital pots. You need two sets per channel, so you'd need 8 total DS1801s (they have two pots each), and 6 control output pins on a microcontroller to run them. You could also program this array using output pins on a parallel port of a PC. However, the microcontroller would be far lower power, which is an important consideration for you, I think. Again, the outputs of corresponding 'channel' outputs would go to different opamps, set up in an analog adding configuration, so you could add the two channels together. The output of each of the addition modules would be to the power amp for that speaker, which could be as simple as MAX9716, a single channel power amp. You'll want to keep it lower power to conserve battery power anyway. If you were brave, you could probably hack up discrete digital logic to do the three wire control without using a microcontroller; however, a microcontroller would be the easiest thing. Using the microcontroller (or PC), you could easily experiment with various kinds of rolling motions, delays, etc, quite easily. Regards, Bob Monsen
ok... so assuming I'm going to take the non-complex approach to this problem, and use a 555 timer RC controlled -> counter -> 8 channel multiplexer, other than the datasheets, how would I go about actually getting some kind of schematic together? such as example schematics that use these chips together, or seperately.... Im capable of hooking it all up, but the datasheets are pretty dense with technical jargon. I suppose the best thing to do would be to get the chips in hand and hook 'em up to a breadboard and see if they work, eh?
Note that you will still have the clicking with this method, since you will still have abrupt transitions in the waveform. You will also need a power amp for each channel, since the multiplexer will only handle low-level signals. So the upshot is that if you can tolerate the clicking you already have with a rotary switch, you may want to stick with that... it won't improve with the electronic multiplexer, and it would cost a lot more. If you want to get rid of the clicking, you have to control the rise/fall times of each transition. Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis www.daqarta.com
What Bob said. I suppose this horse is pretty well beaten by now, but I'd sure use linear volume control at line level into the amps, as opposed to hard switching of speakers. And with smooth modulation of volume, you could probably get exactly the effect you want with only four speakers (two stereo amps would do the trick). -- John Miller Email address: domain, n4vu.com; username, jsm In Brooklyn, we had such great pennant races, it made the World Series just something that came later. -Walter O'Malley, Dodgers owner
