Show HN: Hacking an ultrasound probe with a Raspberry Pi and low-cost hardware (opens in new tab)

Ah, that makes a lot of sense - I was trying to find information on how ultrasound machines worked awhile ago, and most of the information I found just said that a ceramic piezo is used to emit the sound and measure the time until it returned. I could not fathom at the time what kind of math must be required to get a 2D image out of a single data point like that, and I couldn't find much elaboration on the subject.

But if it's just a few hundred piezos in an array, now THAT makes a lot more sense.

> in the end, it's a matter of life and death

But also if you can't afford one.

Am I allowed to built an ultrasonic probe the way I want if I don't use it on anybody else but me ?

Another potential issue is that ultrasound machines send out an impulse instead of a single frequency. So maybe the quartz crystal oscillators aren't good at producing a short high-bandwidth signal?

That being said, there's a type of radar system called "stepped frequency continuous wave" radar that uses a bunch of single frequency transmissions instead of an impulse transmission. The basic idea is that instead of using a high-bandwidth transceiver to send and receive the impulse, you can use a low-bandwidth transceiver to send and receive tones, and then hop this transceiver over the large bandwidth to get a high-resolution image (the tradeoff being that it takes longer to acquire an image). Since ultrasound is basically radar, I'd imagine this technique could be used for ultrasound too.

Thanks for that explanation. What would happen with the quartz crystal. Would it just not emit the sound or would it crack under the vibrations?

And if it can't withstand the vibrations it generates, how far off would it be from the required energy (many orders of magnitude?)

Actually I fear 5s is far too slow to develop a sense-like feel for it :/

But thank you for the offer to discuss more :)