I'm a relative novice to robotics. What I'm trying to achieve is simulation of breathing in and out via a small airpump that inflates and deflates an air cushion.
Ideally this would be achieved with one airpump of which I can reverse the function. Do such airpumps exist? So far I only found airpumps that have mutually excluding inflation and deflation openings.
Looking for a small airpump on DC preferably, 3V - 12 V range.
The alternative that I currently have is to use two separate airpumps...

 

Do you have room for a motor / crankshaft operating a bellows?

 

The alternative that I currently have is to use two separate airpumps...

.... or 1 pump + 1 N/C solenoid valve.

 

Air pumps are noisy… you may want to include an air reservoir to minimize the time the pump is used.

Having said that, you may not need to reverse the pump. Include in your design, an electrically controlled valve to allow the air in the chest bladder to exhaust to the room. The tension in the bladder and the animatronic body will push the air out through this exhaust valve.

 

If you are trying to simulate human breathing you may find creating a model of the same mechanism is effective. The diaphragm moves up and down expanding and contracting the lungs. A nearly silent mechanism based on a flexible, air tight panel on the bottom on an airtight chamber with an air bladder (think balloon) inside with it’s input-output port open to the air would act like the respiratory system inflating when the panel moves down and so breathing in and deflating when it moves up, so breathing out.

 

Moving air both in and out is one thing, but I wouldn't call that a simulation of breathing. I think of breathing as resembling a sine wave, with the rate of airflow changing throughout each cycle. Is a constant speed, changing only the direction, an acceptable solution?

You MIGHT be able to achieve a variable air flow rate (with a constant motor rpm) with the right kind of valve arrangement. I'm picturing a slowly rotating gate valve for instance. Or you could change the voltage of the power supply to the motor. The electronics of that might be easier than the mechanics of valving. Just spitballing.

And I like Ya'akov's proposal. A simple rotating cam wheel could be arranged to provide the varying airflow rate.

 

Do you have room for a motor / crankshaft operating a bellows?

Indeed not enough space. Thanks anyway for the suggestion.

 

Moving air both in and out is one thing, but I wouldn't call that a simulation of breathing. I think of breathing as resembling a sine wave, with the rate of airflow changing throughout each cycle. Is a constant speed, changing only the direction, an acceptable solution?

You MIGHT be able to achieve a variable air flow rate (with a constant motor rpm) with the right kind of valve arrangement. I'm picturing a slowly rotating gate valve for instance. Or you could change the voltage of the power supply to the motor. The electronics of that might be easier than the mechanics of valving. Just spitballing.

And I like Ya'akov's proposal. A simple rotating cam wheel could be arranged to provide the varying airflow rate.

Thanks for your reply, I will look into valves.

 

If you are trying to simulate human breathing you may find creating a model of the same mechanism is effective. The diaphragm moves up and down expanding and contracting the lungs. A nearly silent mechanism based on a flexible, air tight panel on the bottom on an airtight chamber with an air bladder (think balloon) inside with it’s input-output port open to the air would act like the respiratory system inflating when the panel moves down and so breathing in and deflating when it moves up, so breathing out.

Interesting approach. My current design will not provide enough room

.... or 1 pump + 1 N/C solenoid valve.

Thanks for the idea, I will look into valves.

 

Moving air both in and out is one thing, but I wouldn't call that a simulation of breathing. I think of breathing as resembling a sine wave, with the rate of airflow changing throughout each cycle. Is a constant speed, changing only the direction, an acceptable solution?

You MIGHT be able to achieve a variable air flow rate (with a constant motor rpm) with the right kind of valve arrangement. I'm picturing a slowly rotating gate valve for instance. Or you could change the voltage of the power supply to the motor. The electronics of that might be easier than the mechanics of valving. Just spitballing.

And I like Ya'akov's proposal. A simple rotating cam wheel could be arranged to provide the varying airflow rate.

Thanks, I will explore valves. Indeed a variable flow would allow variable breath simulation, adding the possibility to mimic different moods, such as anxiety/relaxed/exhausted. Will keep this in mind

 

A peristaltic pump might fit the bill. Variable speed by controlling the motor speed and they are generally reversible.

 

Thanks for your reply, I will look into valves.

Are you trying to make some sort of medical instrument for training of some sort?

It is possible that the air pump has enough leakage such that when turned off it passes air in the opposite direction. Unfortunately, it may be hard to control the rate it probably has a fixed rate.

Following along post #5 idea, a linear actuator will provide complete control over inflate and deflate modes.
Keep in mind there are different ways to breath. Normal breathing would be when the person is relaxed, and fast breathing after activity. Also, and this is a little funny, taking very deep breaths when trying to relax (ha ha), and holding it, then releasing slowly.

This may sound a little funny too. I would not use a regular party balloon as they are subject to breakage. Perhaps a special type of balloon and even a condom (ha ha) if you don't have to have the full volume of a pair of actual human lungs. If you do need that, you have to find out the average volume of air most human lungs can take in, probably something like 300 cubic inches but don't quote me on that.

 

A peristaltic pump might fit the bill. Variable speed by controlling the motor speed and they are generally reversible.

Thanks, I ordered one. One single pump fits best in my current design.