[Lab] The Big Plan - Chris B

Roman Gargulak roman at cncwings.com
Fri Mar 15 09:09:54 EDT 2013

At first, I also thought about a microphone solution with simple 
passband filter that would be tuned to the ventilator sound, but using 
pressure sensor makes much more sense IMAO.

Someone already posted link to the Digikey website with suitable sensor 
(credit goes to that gentleman):

It has pressure range from 0 to 83cm H2O and proportional analog voltage 
output from 0V to 4.75V, ideal for this application.
That can be tied directly to a comparator circuit to produce a voltage 
depended PWM. Simple circuit with few op amps, some transistors, few 
resistors and caps.
Done, no programming required.

As pressure rises duty cycle increases, pressure collapses, duty cycle 
decreases, no pressure, 0 duty cycle.
Or the whole process can be inverted as needed.

Sensor is about $15, all the other components would be in the same ball 
park, $15-$25.
The most expensive part would be the LED light. I stopped at the Battery 
Expert here in Orleans the other day and they have nice 12V emergency 
LED lights that may be good for this project.
Not cheap though, $75 for this fixture 

just my $0.02


On 3/15/2013 8:41 AM, Michael Sepa wrote:
>     Chris,
>     The clarification of the project really helps out.  I looked up
>     the manual for the Puritan Bennet LP10
>     (http://www.meql.com/Manuals/Puritan-Bennett-LP6-Plus-and-10-Ops-Manual.pdf)
>     in the hope that there would be a simple electronic monitor
>     connector on the back that you could hook into, but no such luck.
>      There are pressure alarms that can be set and a remote alarm
>     connection on the back of the machine, but you'll get audible
>     alarms off the machine at the same time.  Not what you intend.
>     One approach would be to do the following:
>     1. Lights start off, no ventilator pressure
>     2. Ventilator turns on, a microphone beside the patient air tube
>     senses flow
>     3. Arduino detects change from microphone
>     4. Arudino uses pulse width modulation[2] to brighten an LED array
>     from off to full on in 1.5s, and holds
>     5. Ventilator turns off
>     6. Microphone detects stop of flow from patient air tube
>     7. Arduino uses pulse width modulation to dim an LED array from
>     current level to off in 1.5s and holds
>     [1] pulse width modulation is just a fancy way to say turn on/off
>     the LED array fast enough to control brightness.  This is built
>     into the Arduino system, so it's very easy.
>     Connecting to and dimming an LED array with an Arduino is well
>     understood.  No issues there.
>     The microphone will require an amp chip to get it producing a
>     signal the Arduino can easily read.  If we can find a pre-made
>     microphone and amp, then it will be all so much easier.
>     The programming of the system would be straight forward.
>      Certainly less than a day of effort.
>     The system would work well if the room was reasonably quiet.  If
>     there was other noise it might trigger the microphone causing
>     premature light adjustment.  A better approach would be to use a
>     pressure sensor.  I checked ebay and see several pressure sensors
>     available, all use I2C interfaces.  That would take a bit more
>     programming effort, but certainly less than a day or two.
>     If you go with a pressure sensor, we'd need to makes sure the
>     sensor has the right range to sense the ventilator pressure.  That
>     I couldn't get from the quick ebay search because they don't
>     usually publish specs with sale items.  I'm confident  we could
>     find an appropriate one on ebay, spark fun, or somewhere else.
>     As for your budget, I'd think you should have no issues buying all
>     the tech plus paying someone a small honorarium for helping you
>     program it all.
>     My big question would be what's your schedule?
>     -Michael Sepa
>     Date: Thu, 14 Mar 2013 17:49:08 -0400
>     From: The Big Plan - Chris B <tbp at ghostwise.com
>     <mailto:tbp at ghostwise.com>>
>     To:lab at artengine.ca
>     <mailto:lab at artengine.ca>Subject: Re: [Lab] Controlling Light with
>     Sound
>     Message-ID: <F3148EB9-8831-464E-92AA-2144AB15E72B at ghostwise.com
>     <mailto:F3148EB9-8831-464E-92AA-2144AB15E72B at ghostwise.com>>
>     Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
>     Hi everyone,
>     Thanks for the awesome replies so far. I think I should clarify my
>     intentions:
>     My plan is to suspend a loose canvas that is approximately 7 by 11
>     feet on an angle from the ceiling.
>     I would like to put lighting behind it (I don't know what lighting to
>     use or whether it
>     should be a set of lights). The rest of the room will be dark.
>     A ventilator (Puritan Bennett LP10) will be on the floor. Every
>     breath
>     of the ventilator
>     should cause the lights to turn on in a gradual way and then dim dark
>     as the breath
>     ends. Each breath should take about 1.2-1.5 seconds.
>     I like the idea of an Arduino or Raspberry Pi controlling the
>     lighting.
>     It sounds like I will also need a mic by the ventilator.
>     Finally, I have zero programming experience or overall technical
>     experience to do this. I'm the artist
>     with a vision. I would appreciate assistance from anyone
>     interested in
>     this project.
>     It would be great if it could be done on a $250-500 budget.
>     Thanks in advance,
>     Chris
>     On 14-Mar-13, at 4:11 PM, The Big Plan - Chris B wrote:
>>     Hi!
>>     Looking for some advice for an art installation. I'd like to have a 
>>     light or set of lights respond to an auditory
>>     input. I'd like the lights to turn on in time with the sound of a 
>>     ventilator (a medical one). So when the ventilator is
>>     not doing a breath, the lights would be off, but then when the 
>>     ventilator starts doing a breath they would
>>     turn on for the duration of the breath. I'd like the lights to light 
>>     up and dim gradually, not just on an off.
>>     What's a simple or best way to do this?
>>     Thanks!
>>     Chris
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