pypilot store open again

[ironman]

Ive seen that project but not sure it will really work that well given the design choices.

As for 80cm,  is a challenge.  Especially if the transducer is at this depth and only a few cm from the bottom.

By the time the pulse is received, the transducer is still ringing from transmit, so it is hard  to measure.

My boat draft is 60cm, I will be trying also at shallow depths,  I think it might have to detect depth an adjust pulse length, perhaps use active dampening and so on.

Despite this other depth sounders I have used can measure below 1 meter depth so not sure exactly what you are doing.

Interested to here what design choices you have issues with? I run an open echo device on my yacht and it works perfectly (I have personally tested down to about 20m, I know others have seen down to 40+ but I have not been anywhere that deep recently). It even works with either of my on board transducers, a 1970s 150kHz and an early 2000s 192kHz, both of which are bonded to the hull.

My 150kHz has a very small ringdown, around 30cm at the voltage I am driving it at (~30V), so would work well for a shallow draft like yours I guess?

So you say the smaller the voltage, the smaller the ringdown, and the shallower the depths that can be measured?

[johnch]

Well this is great to hear from someone using open echo and get feedback as I had not seen much besides one youtube video.

Yes!  certainly the ringdown at only 30 volts is less time, and this is the right solution, if it detects the depth is shallow, then it can use less voltage and shorter pings to reduce ringdown time, so it can work adaptively.  I also intend to experiment with active dampening as well.

I think one of my main issues with open echo is it does not sweep frequency in a chirp.  So correct me if I am wrong, but what I am doing is also allowing a variable bandwidth, and the pulse is sent sweeping this bandwidth.  Some transducers have wider bandwidth than others.  The return is then computed a FFT, along with FFT of the chirp and these are convolved in frequency space then inverted with IFFT.    This mathematically produces a much sharper depth measurement, in fact it allows accuracy down to centimeters (the exact resolution depends on bandwidth)  while allowing the pulse energy to spread across several milliseconds which it is not possible with a simple ping,  this is the "chirp" sonar.

So this is my issue with the ti part the tuss4470, it has many limitations, and although it is much cheaper,  the electronics I have are still cheaper than the transducer itself.  Most transducers can handle higher voltages (up to 100 volts) which results in potentially (depending on unit again) both higher efficiency from much shorter pulse needed as well as better clarity and certainly more range, but this part limits driving to about 30 volts, probably designed for air not water??

If 30v works at 40 meters then this is less of a question, but probably at only 200khz or less though that is quite good to know.  Perhaps the analog receiving part is very good.  At higher frequencies like 800khz much more power might be needed and those higher frequencies have much better resolution and are desirable for mapping or imaging.

Eventually for a phased array with many elements, I dont think the TI part could ever be used as the channels would not be synchronized in time so no way to perform the beamforming computations.

If a cheaper transducer (< $20) can be found or reusing an existing one, then the open echo in absolute terms is much cheaper, especially to just get depth, and this is interesting and useful for that reason, but I am trying to produce higher resolution images with more user configurable variables, and the cost $30 or $40 more for the electronics.  What do you think?

Hmm, yes I think maybe you have somewhat different goals. OpenEcho was designed as a development platform to make basic sonar very easily accessible, and most users who have installed it as an echo sounder are generally (like me) reviving an old installed transducer at minimal cost, for which it is ideal - especially as most marine transducers found in older boats will be in the 150-200kHz range. 

I have seen people drive a 1MHz transducer with it, but the range was very limited due to the lack of power as no transformer was used. It is possible to add a transformer between the TUSS and the transducer to increase voltage further, but then you get into things like impedance matching which mean the setup becomes specific to one transducer, and since most users don't need more than the performance we are getting at 30V we haven't done a lot of testing with transformers.

I agree that if doing beamforming etc the TUSS is probably not the ideal hardware. I would encourage you to join the OpenEcho discord though, there is a good community of people there working on a number of related projects (some using OpenEcho, some not) and it would be great to add your voice and your project to those discussions!

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Ive seen that project but not sure it will really work that well given the design choices.

As for 80cm,  is a challenge.  Especially if the transducer is at this depth and only a few cm from the bottom.

By the time the pulse is received, the transducer is still ringing from transmit, so it is hard  to measure.

My boat draft is 60cm, I will be trying also at shallow depths,  I think it might have to detect depth an adjust pulse length, perhaps use active dampening and so on.

Despite this other depth sounders I have used can measure below 1 meter depth so not sure exactly what you are doing.

Interested to here what design choices you have issues with? I run an open echo device on my yacht and it works perfectly (I have personally tested down to about 20m, I know others have seen down to 40+ but I have not been anywhere that deep recently). It even works with either of my on board transducers, a 1970s 150kHz and an early 2000s 192kHz, both of which are bonded to the hull.

My 150kHz has a very small ringdown, around 30cm at the voltage I am driving it at (~30V), so would work well for a shallow draft like yours I guess?

So you say the smaller the voltage, the smaller the ringdown, and the shallower the depths that can be measured?

You have a few options for reducing ringdown - how you mount the transducer (if it's mounted well this shouldn't really be a factor, but poor bonding can increase ringdown), the voltage, and the number of pulses. But anything that reduces ringdown will likely also reduce the power output and therefore range, so there is a tradeoff there.