Pressure Sensors for Surgical Simulator

[sugarf...@gmail.com]

Hello all Arduino programmers!

We are working with a thoracic (chest) surgeon to develop a video-assisted thoracic (VATS) simulator. This simulator helps teach minimally invasive surgery techniques as an alternative to open chest surgery as there are fewer complications, a shorter hospital stay, less pain, a quicker recovery time, etc.

We have developed a complex synthetic and functional hydraulic system (primarily out of silicone) to simulate the lungs and heart and in that process use an Arduino to control the systolic and diastolic blood pressures. So, we are "good" with this most important aspect of the simulator.

However, one complication to minimally invasive surgery can be aggravation of the intercostal nerves that run just below each rib. This can be caused by the surgeon pinching the nerve between his instrument(s) and the rib.

As a result, we have devised a resistive VeloStat pressure sensor at the bottom of each rib and need to devise a little better than "basic" Arduino sketch. We are not programmers and so are looking for help!

Ideally, we would have a tone generated when as certain minimum pressure is reached (that can be adjustable) and the tone would get louder or increase in pitch as more pressure is applied. This would alert the surgeon that he is pinching a nerve when his attention is understandably on other aspects of the surgery. It would be a bonus if there could be a calibration routine when the system is energized.

Any help would be greatly appreciated!

Thank you in advance for your consideration.

[Chris Weiss]

have you worked out reading the pressure and generating the tones you
want separately? the map() function is handy for taking an input
range and transforming it to an output range.

I'm not sure how you'd change the sound volume though, sound isn't
something you normally do with just an arduino, and in the cases where
I have volume is not controllable.

[sugarf...@gmail.com]

We have 16 sensors in 3 groups. Each group now has a voltage divider and the output is a simple piezo buzzer. The buzzer volume proportionately changes with pressure.

So, I'm not sure what you mean by 'reading the pressure', but that is our crude system right now.

[Chris Weiss]

could you use a digital pot to adjust the voltage divider to affect
the sensitivity? arduino's don't have a DAC, only PWM output, so they
can turn a buzzer on an off really fast, but it's not the same. you
might be able to add a SPI or i2c DAC, but some other other audio
system that has volume control is likely better suited.

[sugarf...@gmail.com]

Would the digital pot allow for a software routine to adjust sensitivity?

Can you tell me what an SPI is?

Thanks!

[Chris Weiss]

SPI is a type if serial protocol.

a digitial pot will allow you to adjust analog resistance from an
arduino, but they aren't able to carry much current.