Using line-level analog audio signals to trigger lights.
thoughtprocess01
Posts: 1
I'm considering undertaking a project to control lights for my band using analog audio signals corresponding to individual drum hits. My sound card can provide a line-level out for each drum. I included a screenshot of the software I record with in order to give a feel for what I'm doing. The point just pass the cursor shows a roll down the toms that would be awesome to sync to colored lights.
I have a few issues to figure out, though. I know I'll be using a BS2 to sample the analog audio and convert it to digital. What I'm wondering about is interfacing the input and output, and also whether or not I can get away with not buying an ADC chip.
First of all, I expect to be using unbalanced 1/4" audio cable to get the audio out of the sound card and into the microcontroller. I read on the internet that these types of connections expect 50 kohms of recieve impedance. I was wondering if I should use a high gain op-amp to take care of this requirement and to "square off" the signal so that the BS2 can understand it. If not, then will resistors do the trick (see graphic below)?
Secondly, I'm wondering about the best way to interface the logic outputs of the microcontroller to the 120 VAC lights. I've used MOC3011 optoisolators before, but found that they have a tendancy to get hot after a few minutes of switching at even modest frequencies. This wouldn't be a problem, but apparently heat is enough to turn on the phototransistor inside and they freeze "on" until they cool. Another option is relays, but they're expensive. Also, the problem with both of these options is that they provide only on/off capability and I would have a hard time implementing PWM fading (for instance to match the transients of a crash cymbal hit). Perhaps a relay is fast enough to do this, but I'm thinking there's a better solution.
Thanks for any input that any of you have,
Jon
I have a few issues to figure out, though. I know I'll be using a BS2 to sample the analog audio and convert it to digital. What I'm wondering about is interfacing the input and output, and also whether or not I can get away with not buying an ADC chip.
First of all, I expect to be using unbalanced 1/4" audio cable to get the audio out of the sound card and into the microcontroller. I read on the internet that these types of connections expect 50 kohms of recieve impedance. I was wondering if I should use a high gain op-amp to take care of this requirement and to "square off" the signal so that the BS2 can understand it. If not, then will resistors do the trick (see graphic below)?
Secondly, I'm wondering about the best way to interface the logic outputs of the microcontroller to the 120 VAC lights. I've used MOC3011 optoisolators before, but found that they have a tendancy to get hot after a few minutes of switching at even modest frequencies. This wouldn't be a problem, but apparently heat is enough to turn on the phototransistor inside and they freeze "on" until they cool. Another option is relays, but they're expensive. Also, the problem with both of these options is that they provide only on/off capability and I would have a hard time implementing PWM fading (for instance to match the transients of a crash cymbal hit). Perhaps a relay is fast enough to do this, but I'm thinking there's a better solution.
Thanks for any input that any of you have,
Jon
550 x 708 - 117K
Comments
Google Vox setups as HAM radio guys would use them. I think some setups will detect the audio and then trigger something....what you need to do is set up some frequency filters to differentiate between teh different hits.
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Steve
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."