Ultrasonic flying spot scanner NBTV

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Ultrasonic flying spot scanner NBTV

Postby Harry Dalek » Fri Aug 16, 2013 12:21 pm

Another crazy idea perhaps might work ? How about a normal Nipkow with a ultrasonic transducer transmitter used instead of the and led array ?
Perhaps the high frequency sound might pass the scanning holes and scan a 3d object and use a receiver transducer as in a flying spot scanner idea to pick up the sound bouncing off the 3d object and processing the signal as per norm ?

I suppose it might cause vibrations in the disk if turned up to high and not sure if the reflected sound off the disk would cause a problem it wasn't that much a problem on the first flying spot scanner with the wasted light and head amp .

I haven't really looked into how ultra sound imaging is done but i don't think they use a nipkow :wink:
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby Panrock » Fri Aug 16, 2013 5:33 pm

Sonar imaging. Great! :D

I think, if using standard 40KHz transducers, you might find the 8mm wavelength a little long for effective directional control by small Nipkow holes. And unless you used a disc made of sound absorbing 'carpet', most of the sound would be reflected straight back.

Where ultrasound could come into its own is 'broadcasting' the NBTV signal across a room. Your signal would be inaudible but I recently experimented with audible modulated hf sound for tinnitus suppression. However it proved a blind alley for this and sounded rather like the 'chirruping' line timebase on a 405-line set running off-sync.

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Postby Harry Dalek » Fri Aug 16, 2013 7:25 pm

Hi Steve

Panrock wrote:Sonar imaging. Great! :D


I was thinking about it as i have a few transducers i got off ebay a while back . it would be interesting if any sound would pass the tiny hole as in light i would expect a large drop in signal ...may be it shouldn't be a hole but a tiny membrane to revibrate the air infront of the nipkow .

I think, if using standard 40KHz transducers, you might find the 8mm wavelength a little long for effective directional control by small Nipkow holes. And unless you used a disc made of sound absorbing 'carpet', most of the sound would be reflected straight back.


I was thinking there would have to be some change in the standard nipkow if tried where as in a light one we want it thin as perhaps a sound one a nice thick one or as you say foamy thing layer behind the disk infront of the transducer .

Perhaps it would be no good for close up 3d objects but better at stuff at distance ? but seeing ultra sound imaging it is possible just as you say would a nipkow of some form do the trick would be interesting to try and see what happens.

Where ultrasound could come into its own is 'broadcasting' the NBTV signal across a room. Your signal would be inaudible but I recently experimented with audible modulated hf sound for tinnitus suppression. However it proved a blind alley for this and sounded rather like the 'chirruping' line timebase on a 405-line set running off-sync.

Steve O


http://reviseomatic.org/help/x-ultrasou ... ceiver.php

This guy did it with slow scan television it would be no problem to do it with NBTV the transmitter and receiver are shown circuits here but would just need a unmodulated 40khz transmitter for a camera idea for any experimenting .

I have never really ever played around with them but when get around to make a transmitter receiver i would try out shooting the signal at a tiny hole to know.

May be the 2 rotating shapes reflecting for sound scanning might be another idea but as you again think perhaps the wavelength is to large for the small amount of lines ...may be it would work but there would be a large lack of detail ...may be good for shapes still looking at ultra sound imaging it has me wondering.
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this ultra sound image looks like its at NBTV standard lines
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Postby Panrock » Fri Aug 16, 2013 10:18 pm



Interesting site!

Here's an ultrasonic receiver I built up from a Maplin kit some years ago. It's tunable between 20 and 160 KHz !

Steve O
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Postby Harry Dalek » Fri Aug 16, 2013 11:23 pm

Panrock wrote:


Interesting site!

Here's an ultrasonic receiver I built up from a Maplin kit some years ago. It's tunable between 20 and 160 KHz !

Steve O



Thats nice range ! i didn't know they could go up that high ,so you must be able to transmit to that frequency too.
Did you have a transmitter as well ? that would be good for NBTV sound wave transmitting .

Yes thats a nice site and simple circuits wonder why he didn't just modulate to pin 5 of the 555 timer its simple but i think you can simple it down more .
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Postby Harry Dalek » Tue Aug 20, 2013 11:07 pm

Had a bit of time to knock this together haven't tested it yet ,I like the idea of having a U.S transmitter and receiver .
http://www3.telus.net/chemelec/Projects ... onic-1.htm

I hope it works, i changed the the transistors for common BC548 seemed to me to be the best replacement i had for 2n5088s....i also changed the opamp
for a TDA2822 see how that gos, i also replaced the R1 and R2 fixed resistor switched with a pot that seemed a better idea .

Might be good for NBTV experiments like transmitting or a ultrasonic encoder idea ,always wanted to see if i could do some laser experiments using the vibrations so might be a useful for the NBTVER.

The transmitter i am still working on they seem a lot simpler than the receiver .
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Postby Harry Dalek » Sun Aug 25, 2013 5:17 pm

Been thinking a bit more on the ultra sonic side of things ,i finished my receiver and transmitter .

I changed the receiver design ,i made a mistake shorting out the transducer in the schematic from the last post which i didn't find till i ripped all the transistors resistors off the board...arrrrrrrr :oops:

Any case i used a few ideas and made this frankenstein ultrasonic receiver which seems to work well.

The heterodyning is optional and can be feed to either the second stereo amp of the Tda 2822 then you could switch between the 2 with or with out heterodyning that tda 2822 is a stereo amp i ripped out of a little b/w tv just had it handy .

I finished the transmitter as well, i will post the schematic but i have to do some transmitting tests i want to hook up that old i phone i showed in off topic with the NBTV wave files and transmit those via the ultrasonic transmitter and hook the receiver up to my laptop and see if i and view any thing with Garys viewer.

If its got the bandwidth and i would like to go on to other experiments and see if i can scan the ultra sonic signal , rethinking the scanning idea i think a rotating sold polygon to do the line scan and a rotating Square for the frame.....might be a better less lossy idea for the signal.

I am not sure about the focusing part if it would need a ultra sonic version of a optical lens .

Just see how it gos if its worth going on with.
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby Harry Dalek » Sun Aug 25, 2013 11:17 pm

Well did a Quick transmit of nbtv i can hear it in the receiver i just need to plug it into the laptop to see what Garys software makes of it .

This is interesting

http://www2.warwick.ac.uk/fac/sci/eng/r ... /focussed/

They don't say how the raster scanning is done but wonder if you could do raster air scanning with just speakers noise and all.
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Postby Harry Dalek » Sat Aug 31, 2013 7:55 pm

Well i have had a week of frustration so far trying to receive NBTV via transducers , what does work fine is voice and Slow scan television both work great in fact Slow scan is easy peasy ...

Nbtv i am finding pretty hard i tried 2 different transmitters the one above and a PWM version....which i have used with laser works now for slow scan via a transducer so i know it has the bandwidth.

I think i will have to brake the transmitting down and see whats up perhaps a good start would be to check my 400hz sync is making it across to the other transducer i think this might be the problem perhaps also i should do a frequency sweep test .
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Postby gary » Sat Aug 31, 2013 8:20 pm

You should do a sweep - do you have the means of doing so? Just a wave file played out of your PC/laptop will do. If you can't create a wave file I can post one.
Perfecting an NBTV system is like trying to slam a revolving door...
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Postby Harry Dalek » Sat Aug 31, 2013 8:47 pm

gary wrote:You should do a sweep - do you have the means of doing so? Just a wave file played out of your PC/laptop will do. If you can't create a wave file I can post one.



Yes Gary i can do it live but thinking about it i need a wave file of it ...i am using that old i phone as my wav file player so i need to copy the wav file to that .

So yes please :)

I was getting some results the other day but i think from tests today it was just Rf pick up ...has any one done ultra sonic NBTV transmitting you may have seen in a news letter ?
I am sort of thinking its a sync problem as i was getting better results with speakers a while back perhaps its the transducer problem...need to do some tests .
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Postby gary » Sat Aug 31, 2013 9:43 pm

Here is a 1Hz - 10kHz sweep Harry
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Postby Harry Dalek » Sat Aug 31, 2013 10:19 pm

gary wrote:Here is a 1Hz - 10kHz sweep Harry


Thanks Gary

I just put on my iphone i should be able to do a test tomorrow afternoon.
Once again nbtv has to wait a bit ..:?
Also want to see if i can find a better player app for this phone it will only repeat play on manual bit of a pain on short wav files.

These are the transducers i am using

Thesetransducers are very useful in making various sensors for detecting obstaclesand measuring distances

Applications

1. Obstacle detection

2. Liquid level measurement

3. Obstacle avoidance robot

Features

· Use for motion or distance sensing

· Frequency: 40kHz ±1.0kHz

· Aluminum case

· Capacitance: 2000Pf ±20%

· Transmitter: bandwidth 5.0kHz/100Db,sound pressure level 112Db/40 ±1.0kHz

· Receiver: bandwidth 5.0 kHz @ -75Db, min.sensitivity 67Db/40 ±1.0kHz (0Db vs. 1V µbar) R=3.9k.

Lead length/spacing: 0.28”
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby gary » Sat Aug 31, 2013 11:33 pm

I am afraid I can't have any sympathy with regards your iPhone Harry - I am not rich enough to have one... at least not rich enough to waste money on them. ;-)

You should us a Raspberry Pi! :-)

BTW, given that your transmitter is, I think?, an FM modulator - how is your receiver demodulating it?
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Postby Klaas Robers » Sun Sep 01, 2013 6:14 am

In principle you should use a signal centered around 40 kHz. That is the optimum working frequency of these transducers.

So you should use a modulated carrier of 40 kHz, but then the bandwidth gives the next limitation. It is ± 1 kHz for these transducers, while NBTV needs a base band bandwidth of 10 kHz, that is ± 10kHz if you use AM (Amplitude modulation). For FM you need even more bandwidth.

Then you run into the next difficulty: reflections! With a sound frequency of 40 kHz all walls of a room and all furniture will reflect the sound. And as adjacent dots in an NBTV picture are travelling in the sound wave at a distance of just 1.5 cm apart, all reflections will mix up your received signal. Only abroad this may work, as there are no reflecting subjects, at least if you do your experiments in a desert or at the beach.

Good luck! You will need it.
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