pump controled airflow

Interactives

I am working on a prototype for a kiosk for children to hear what the·call of a parasaurolophus (dinosaur) would sound like, as predicted by various science types. The idea is to have a hand pumped bellows control the air flowing through the sound making device, and the out the head cavity of a cast reproduction of a parasaurolophus head- so that it "breaths" out through the nostrils at the same time as making this sound. Kids seem to like that sort of thing. At first I thought that I could just link the output of the bellows to the control handle of the compressed air system, but that didnt pan out. I was wondering if you think it would be possible to take a dc blower, and hook it backwards to the output side of the hand pumped bellows, then read the slight voltage ( ac most likely) that would be induced in the coils of the blower, send that voltage to STAMP to be analyzed, then have STAMP control the voltage (and therefore intensity) of a much larger blower according to the input signal, that outputs through the nostrils of the dino. so it would be something like:
Bellows blow air into the blower, thus producing low voltage ac which, is sent to analog to digital converter, which is sent into STAMP, STAMP reads the voltage and outputs to a voltage regulator, which controls the much larger blower according to the intensity of the bellows.···· Sound good. Too much? Insert easier solution here:

Stephen Swanson (Parallax)

Interactives,
···········
··········· I have a question, do you need the hand pump in the design? Or could it replaced with a different type of physical control?


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Stephen Swanson
Technical Support
Parallax, Inc.
sswanson@parallax.com


Post Edited (Stephen Swanson (Parallax)) : 5/16/2005 10:29:02 PM GMT

Paul Baker

How about something which was designed to easily turn in the air, like a pinwheel. Then use an IR emitter/detector to count the number of interruptions.

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steve_b

Do the bellows have to actually regulate airflow?
Just put a microswitch at the air output of the bellows...but a large "wing/fin" on the microswitch so that it catches air and closes. Then just look for that 'state' with the stamp and use the stamp to do the rest of the control.

Maybe get a small compressor w/ reservoir. Then you can fire a blast of air out the nostrils immediately followed by the noise and then another blast of air!! Like a snort!
Not sure if this is how the animal would actually do it....but most animals today will snort when confronted (before attacking anyhow).

You can use the stamp to control a pneumatic valve that would open and give you your blast of air.
It is a bit of a pain to have a single compressor/reservoir for one small attraction....but if it's there, then you can run other attractions off of it too! All with their own regulators/solenoids.

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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"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."

Interactives

Well, actually I was kind of hoping to avoid running compressed air to the system- it can be done, because we have compressed air at other points in the exhibit, but it's a ·pretty costly addition. As for the limit switch, we were kind of hoping to have the intensity of the pumping control the intensity of the output, just because it seems more fun that way. If you only have two states, off and on, then it's pretty impractical to have bellows in the first place instead of a push button. I was thinking about the whole IR interrupter thing, because I have some track balls sitting around that I could hook up to a paddle wheel (pinwheels even better)- but then I was worried about the code for that. So far I've been able to do most of my projects with simple pushbutton inputs- so I kind of suck at the whole programming end of things. I know I would have to have the STAMP respond to a input signal that would be constantly changing, and that would change the output accordingly. I guess it would be something like IF input equals a signal hit from 10 to 40 times per second (or nano second?), THEN out put X, IF input equals a signal hit from 41- 80 times per second, THEN out put Y, et cetera. I know that twelve year olds across the country can do this stuff to make their battle bots kick a**, but still it seems like a conceptual ocean to cross for me. Digital math- yuuckk!· So, the consensus seems to be that reading the signal from a blower or DC· fan would actually complicate things , huh? Smile.

Paul Baker

Its not that your original idea is a bad one, its just that there are some easier ways to accomplish the same thing. The main problem I see with your orignal idea is that DC blower fans were designed to be driven rather than being a generator, I would be concerned the friction and intertia of the DC blower would be high enough to lose a considerable amount of efficiency, plus the inertia of the DC blower would introduce a measured delay of a few seconds due to the slow startup/stop. As you know the analog output would require an ADC which adds another level of complexity to the system. If I were to use the DC fan idea, I would likely go with an 80 or 120mm computer case fan (less system inertia) and write code that would chop off trailing data when the fan is in free-spin deceleration.

If I were to write up code for the IR idea, I would set it up that the stamp counts the number of pulses on the detector signal line using a timeout value around a second, then send this value (raw or processed) to the device that acts upon the information, and repeat the process.

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steve_b

You could also detect 'air motion' with a temperature sensor.
MEarly another idea to confuse you with!! haha
BAsically, the temperature will cool (think wind chill) as air passes it....the faster the air, the lower the temp dip.
Now, you would still want a reference sensor so you could say, IF tempsensor1 - tempref1 is less than 10 (saying that the temperature dips by 10deg) then do something....
You can get digital temp sensors (DS1620 I think) that you won't need an A/D converters for...but they are a tad more pricey.

You can then look at ranges of temp changes. If the dip is only a difference of 3...then do this...if it's more than 3 but less than 10..then do this....if it's more than 10...then give'er some good stuff!! lol

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Steve
http://ca.geocities.com/steve.brady@rogers.com/index.html
"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."

Interactives

"If I were to write up code for the IR idea, I would set it up that the stamp counts the number of pulses on the detector signal line using a timeout value around a second, then send this value (raw or processed) to the device that acts upon the information, and repeat the process."

My head is spinning from this one... the "device that acts upon the information"- can that be the STAMP ? or would I need an external processor? Or do you mean the blower?

(Im sorry I'm not very quick to respond to the posts here, I kinda have to check the forum every few hours @ work, but I do appreciate all the help I find here!)

Paul Baker

Im refering to the output blower as the "device that acts upon the information", and the same stamp could be used to do both the input measurement and output control.

Stephen Swanson (Parallax)

Interactives,
··········· In that case since you want to keep the pump, your setup should work as you mentioned above. You will just need to do the following. For the dc blower you will want to hook it up to a voltmeter the + and – pins and measure the voltage (it should be DC if it is a DC blower). Once you get the max output of the DC blower you will then be able to determine if you need to cap the voltage at 5vdc. Once you have that done you can then feed that in to an A/D converter connected to the Stamp.


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Stephen Swanson
Technical Support
Parallax, Inc.
sswanson@parallax.com