# Output from a sound card

Hi,

I’m a student in electrical engineering and working at the Notre-Dame Hospital (CHUM). I’m working on a device that will stimulate the fingertips so that the patient can receive mechanical stimulis, with which fMRI (imaging of the brain’s function to help the doctor operates without touching the functionnal area).

What we’ve come up with so far is using piezoelectrical transducer and use the sofware to send wav files to the piezo transducer. but the problem is that those piezo needs huge amount of voltage to produce small (Âµm) displacement. So what I would like to know from you guys is the normal output of a PC sound card… is it Â±600mV, 0-600mV, Â±5V,… I would need this to be able to build an amplifier that will get the voltage to around 400V or more. I know I could go check it out of my PC, but for now I’m designing the circuit, so I need a baseline since their’s SOOOOOOOO much to think about and I can’t find this info nowhere.

A huge thank you

Hi and Welcome!

for the output levels of a sound card, see here: http://en.wikipedia.org/wiki/Line_(electrical_engineering).
Since this is “Line” signal, it could be amplified using ordinary audio amplifiers.

Michael

That sounds like an interesting project. What’s the nature of the transducer that they require so much voltage (I’m assuming very little current)? Piezo tweeters are fairly common in HiFi speakers and they only use tens of volts. What is the frequency range you’re trying to use these Piezos at?

Thank you for your input mciahel for the link, it was what I wanted to know.

The piezo I was looking at when I wrote the thread where top notch piezo transducer (wayyyy overkill) and they where made for high voltage, for higher displacement. The piezo’s vibration amplitude is linear to the voltage induced… the piezo I was looking for where able to sustand huge amount of voltage so the displacement was much bigger with good amount of force.

The frequency range of mechanical sensor go from 0.3Hz to 500Hz. Pass that point you won’t feel the difference. Much like sound with which pass a certain frequency you can’t hear it.

Today I was looking at different piezo transducer and found what you’re talking about, piezo in the 30V or less… and way much cheaper (less than 1\$ vs 40\$)… but I still need to test those to see if the force applied is enough to trigger brain activity, also if they contain magnetic material, which can’t happen in a MRI room.

btw, if you want to see the power of piezo http://www.physikinstrumente.com/en/news/fullnews.php?newsid=106

with the application of mechanical design you can build a lot of things from this… nanorobot I think will use this kind of technology… it’s so simple to trigger a movement with so few elements