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1Instructables133,612Views71CommentsBristol, UKJoined August 29th, 2016
Do you want to build your own cutting-edge devices? Directly from the research lab. Ultrasonics, Electromagnetism and more. Researcher at Bristol University interesting in Ultrasound and in general any effects that waves can produce.

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10K+ Views Earned a bronze medal
Contest Winner First Prize in the Arduino Contest 2016
Contest Winner Second Prize in the First Time Authors Contest 2016
Contest Winner First Prize in the Sci-Fi Contest 2016
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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam6 days ago
    Acoustic Tractor Beam

    Thanks to you Fred, that looks amazing.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam1 week ago
    Acoustic Tractor Beam

    Hi. The STL for the bowl is designed to support 16mm diameter transducers. Most of the transducers that I have seen are either 16mm or 10mm diameter. perhaps the easiest way is to scale down the bowl to fit the transducers.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam2 weeks ago
    Acoustic Tractor Beam

    Sounds like a strange behaviour. Could you try to bypass the button pad (the problem may be in it) and directly connect GND to D2 (down), D3 (up) or D4 (reset) with a jumper wire to check if it works properly. Best Regards, Asier.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam3 weeks ago
    Acoustic Tractor Beam

    It is hard to say. The size and power seem ok but the problem may be the phase deviation, especially between the emitter and receiver. Put all the Ts in one half and all the Rs in the other.Best regards. Asier.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 weeks ago
    Acoustic Tractor Beam

    Hi Andrea, if there is no load at the output, it is common to see those spikes in the amplified signal. There should also be some spikes on the top but the scope may cap at 20Volts.Also, in theory sinusoidal waves instead of half-square should be used for feeding the transducers but in practice the transducers are so narrow band that the output is still sinusoidal.The important part is the output of the transducers. You can connect a transducer to the scope's probe and check the sound output.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam1 month ago
    Acoustic Tractor Beam

    Hi Mayank, it could be hard to modify the arduino code without affecting the output frequency. What I would recommend is to reduce the variable BUTTON_SENS until the reponse is as fast as you need and use another arduino to control the D2 or D3 pins as needed (ground to activate them and 1 as default, remember that they are pulled-down to avoid accidental activation by noise).

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam1 month ago
    Acoustic Tractor Beam

    Hi evil_scientist, that is very good work, glad that you enjoy acoustic levitation. You are right for the other arrangements a phased array is required with at least 64 channel, I made a driver board based on arduino that we use for some of our current experiments. Of course, I am planning to release it but it will take some time to put it together. But in a couple of months we want to release a single-axis levitator capable of levitating liquids and ants, as well as a directional speaker. All these projects are based pretty much in the same hardware so I guess that you will enjoy it. Best, Asier.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam1 month ago
    Acoustic Tractor Beam

    Hi Cole,The noises should only be there when you move the bead. Getting popping noise could because not enough current can be provided or one the connections is a little bit loose, do the LEDs also blink with the noise?High pitch sounds are because something is touching the pistons of the transducers, that happens a lot when beads get inside or if you are using metallic grid transducers, the grid is in contact with the piston. You can use a thin tweezer to pull the grid outwards.I see three types of scaling:- distance: a bigger bowl with more transducers.- bigger objects: only way is using less frequency. Which is not feasible since 25kHz transducers are massively expensive.- more dense materials (like liquids): I would suggest to go for a standing wave levitator. I am putting an instru...see more »Hi Cole,The noises should only be there when you move the bead. Getting popping noise could because not enough current can be provided or one the connections is a little bit loose, do the LEDs also blink with the noise?High pitch sounds are because something is touching the pistons of the transducers, that happens a lot when beads get inside or if you are using metallic grid transducers, the grid is in contact with the piston. You can use a thin tweezer to pull the grid outwards.I see three types of scaling:- distance: a bigger bowl with more transducers.- bigger objects: only way is using less frequency. Which is not feasible since 25kHz transducers are massively expensive.- more dense materials (like liquids): I would suggest to go for a standing wave levitator. I am putting an instructables on this one, it can leviate liquids, ants and other interesting samples.Best regards.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam1 month ago
    Acoustic Tractor Beam

    This instructables is not easy: you will need soldering skills, medium knowledge of electronics and sound.However, lot of people managed to build it when they can get the correct transducers. From undergrads to parents working with their kids.I think it is a nice project to get into ultrasonics and acoustic levitation. There will be other coming soon.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam1 month ago
    Acoustic Tractor Beam

    Hi John, whether the marked legs are pointing inwards or outwards is not relevant. What it is really important is to have all in the same way.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam1 month ago
    Acoustic Tractor Beam

    This project uses 16mm, I was using 10mm transducers for the levitator and directional speaker but I will try to put two versions: one for 10mm and another for 16mm.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam2 months ago
    Acoustic Tractor Beam

    Dear SwatBio,Unfortunately, the tractor beam will not be very useful.I am working in a simple single-axis levitator that would easily levitate small droplets of urine. As long as you inject them with a pipette or syringe. It would be complicated to catch them in mid-air.Is that a research work for an university or research center. I am quite use to collaborate with them. I would be very willing to help you.Best regards,Asier.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam2 months ago
    Acoustic Tractor Beam

    Could you check the model of the DC-DC converter? There step-ups and step-down.

    Do not be to hard on him, it is a common mistake. Hope that everything goes alright and if you enjoy the project, stay in touch. I have some more similar projects coming: a directional speaker and a single-axis levitator capable of levitating water and live insects.

    Would there be any possibility of powering the device from a regulated DC just to check how much current it is consuming.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam2 months ago
    Acoustic Tractor Beam

    Some shortcut with the buttons. If they are not pressed the transducers should not click. Do any of the lights blink?

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam2 months ago
    Acoustic Tractor Beam

    yeah 20AWG should be fine. The device takes around 1A or so. Actually now for these kind of devices I use 24AWG. It works fine and it is much easier to handle.

    Could you put a picture of the signals that you see?

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam2 months ago
    Acoustic Tractor Beam

    Sometimes the transducers are very poorly manufactured and have a lot of phase deviation between them. However, only one should not hinder the rest of the device. What is the amplitude of the received signal?

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam2 months ago
    Acoustic Tractor Beam

    The water levitator uses 72 and the directional speaker around 150 I think.

    It should be possible to control the phase change through Bluetooth, I have done it with serial and the functioning is the same. If you have problems just use another Nano that read the bluetooth and puts ground into the pins of the other arduino.Transducers for the upcoming levitator that can levitate liquids (and also for the directional speaker) and that are any of these:Manorshi Black 10mm - 0.34$ - MSO-P1040H07TNingbo Black 10mm - 0.38$ - FBULS1007P-TMurata Black 10mm - 1$- manorshi https://manorshi.en.alibaba.com/- ningbo https://bestgroup.en.alibaba.com/product/987365133-800848321/dog_repeller_ultrasonic_transducer_40khz_black_plastic_ultrasonic_sensor_ultrasonic_depth_sensor.html?spm=a2700.7803228.1998738836.187.TSqSlZ- Murata provider http://www.hklihengic.com/english

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam2 months ago
    Acoustic Tractor Beam

    They seem legit. Do you have a scope or a multimeter to do some tests?Can you test to drive it from a DC adaptor? (anything from 9V to 12V 1A will do)Cheers,Asier.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam3 months ago
    Acoustic Tractor Beam

    Yeah some transducers have phase deviations (I guess because of imperfections in the manufacturing process). In any case, the system will tolerate some deviations. Have you tried putting the bead from the top with a metallic grid (or paper teabag)? https://youtu.be/6YV0lou4L4c?t=7m57s

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam3 months ago
    Acoustic Tractor Beam

    The ones that you link seem alright (and both emitters and receivers will work) but it is hard to say if they will have a big phase deviation.The best I have found so far (value for money) are these: https://manorshi.en.alibaba.com/product/60175991283-800165597/Long_Range_15Meter_Aluminum_Plastic_Ultrasonic_Sensor_Detector_110dB_Sensor.html?spm=a2700.7803228.1998738836.186.LYgvHK

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam3 months ago
    Acoustic Tractor Beam

    1) That is a secondary trap created above the primary Twin trap. It could be a focal point or a bottle trap. We have seen similar stuff before: http://www.nature.com/article-assets/npg/ncomms/20... Supplementary Figure 1.2) In magnetic levitation the object can only be pushed or pulled so you need to use PWM to balance the forces with gravity or an opposite magnet. The control may not be as fast as it should and it is harder. In acoustic traps the forces are naturally converging towards the trapping point. Also the particles are very very light, when we levitate water droplets they are more wobbly.3) I will post a more detailed version of the code, which is a simplification of a 64 channels board that we will publish soon.Cheers,Asier.

    For marking the transducers use the method described in the text (not the one in the video). If you can use exposed wire to connect the transducers to save some time since you will not need to strip them. If you have a scope check the signals at different stages of the constructions to check if things are going as they should. Good luck.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam3 months ago
    Acoustic Tractor Beam

    It overheats? I have been driving these guys for hours and they work like a charm. I do not think there is anything cheaper&better.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam3 months ago
    Acoustic Tractor Beam

    Either some shortcut or flaky connection.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    With a UNO would be pretty much the same. But MEGA has different pin mappings, so it will be quite complex. Anyhow, you can get Nanos for just 2 pounds so no worth the effort.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    Good work Andrea, I have some future projects upcoming such as directional speaker or a simple standing wave levitator that easily levitates liquids and heavy stuff.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    Yeah, poking with a wire could do. All the transducer should have the same polarity since we invert the phase in the Arduino software. Could you double check that A0->In1, A1->In2... One way of testing is to connect the bowl point towards a tray with water (leave 2 or 3 cm gap) and check that the deformation that see in the surface looks (D) like http://www.nature.com/articles/ncomms9661/figures/3 if you get only a spot it means that you are getting a focal point instead of a twin trap and that a half of the array may be reserved.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    Hard to say without a picture but the specs seem alright.

    I think I can see one Jumper missing in the L298N. The jumpers that are the sides of the input signals should be connected (they are the enables), if they are not there that pair of signals will not emit. Apart from that everything seems ok.

    If you have a scope and two spare transducers follow the steps in the https://youtu.be/6YV0lou4L4c?t=6m53s video where you check what each transducer is emitting and be sure that same halves are in phase and opposite ones are out of phase . What is the peak-to-peak of the waves that you read?

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    25kHz transducers are rather pricey and in a tractor beam configuration they are not going to be that useful. But if you want to try a standing wave you may be able to levitate big particles.I was preparing an optimized standing wave setup for levitating liquids and other heavy objects.If you do not want to move the particle around, this code is much easier to select arbitrary frequencies:#include <avr/sleep.h>#include <avr/power.h>//byte pattern = 0b00000000; //all the ports will output the same signalbyte pattern = 0b10101010; //consecutive ports will have an opposite signalvoid setup(){ DDRC = 0b11111111; //set pins A0 to A7 as outputs PORTC = 0b00000000; //output low signal in all of them // initialize timer1 noInterrupts(); // disable all interrupts TCCR1A...see more »25kHz transducers are rather pricey and in a tractor beam configuration they are not going to be that useful. But if you want to try a standing wave you may be able to levitate big particles.I was preparing an optimized standing wave setup for levitating liquids and other heavy objects.If you do not want to move the particle around, this code is much easier to select arbitrary frequencies:#include <avr/sleep.h>#include <avr/power.h>//byte pattern = 0b00000000; //all the ports will output the same signalbyte pattern = 0b10101010; //consecutive ports will have an opposite signalvoid setup(){ DDRC = 0b11111111; //set pins A0 to A7 as outputs PORTC = 0b00000000; //output low signal in all of them // initialize timer1 noInterrupts(); // disable all interrupts TCCR1A = 0; TCCR1B = 0; TCNT1 = 0; OCR1A = 319; // compare match register 16MHz / 319 = changes every 50kHz -> 25kHz half-square wave TCCR1B |= (1 << WGM12); // CTC mode TCCR1B |= (1 << CS10); // 1 prescaler, no prescaling TIMSK1 |= (1 << OCIE1A); // enable timer compare interrupt interrupts(); // enable all interrupts // disable ADC ADCSRA = 0; // turn off everything we can power_adc_disable (); power_spi_disable(); power_twi_disable(); power_timer0_disable(); power_usart0_disable(); while(true); //avoid entering into the loop}ISR(TIMER1_COMPA_vect) // timer compare interrupt service routine{ PORTC = pattern; //output portDV into ports A0 to A7 pattern = ~pattern; //invert all the bits}void loop(){}

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  • Asier Marzo's entry Acoustic Tractor Beam is a winner in the Sci-Fi Contest 2016 contest 4 months ago
  • Asier Marzo's entry Acoustic Tractor Beam is a finalist in the Sci-Fi Contest 2016 contest 4 months ago
  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    You are welcome.It is hard to say, I have tested several models for power and phase deviation; and even when they look the same, they are quite diverse.I have a directional speaker coming and I will publish my comparisson of transducers, but the metal ones from Manroshi are the best I have tested so far.Yeah, more transducers and more voltage equals to denser objects. Although it is a little bit strange, the size does not matter, only the density of the object. Although so far the objects cannot be bigger than half of the wavelenght, we are working on surpassing that limit. But if you want to levitate denser objects I recommend to use a standing wave. We are working in a robot that can pick and process samples in mid-air of densities up to 1.2, so it can deal with water and most of the ...see more »You are welcome.It is hard to say, I have tested several models for power and phase deviation; and even when they look the same, they are quite diverse.I have a directional speaker coming and I will publish my comparisson of transducers, but the metal ones from Manroshi are the best I have tested so far.Yeah, more transducers and more voltage equals to denser objects. Although it is a little bit strange, the size does not matter, only the density of the object. Although so far the objects cannot be bigger than half of the wavelenght, we are working on surpassing that limit. But if you want to levitate denser objects I recommend to use a standing wave. We are working in a robot that can pick and process samples in mid-air of densities up to 1.2, so it can deal with water and most of the stuff.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    Dear Pedro. Could you check these steps and tell me where it fails?1- When you switch it on all the components have lights (L298N, Arduino, DCDC)2- What number do you see in the DCDC converter3- Can you check with a scope that the arduino is generating 40kHZ signals.4- Can you check with the scope that the L298N is outputing square signals?5- put another transducer in the scope probe and put the transducer face to face. Are you receiving a sinusoidal wave, what is the peak to peak voltage?In the video you will see these procedures and the expected results.

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  • Asier Marzo's entry Acoustic Tractor Beam is a winner in the Arduino Contest 2016 contest 4 months ago
  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    In step 33 there are some raw files.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    Dear EuclideanKraken, as you said the levitation will work independently of the bowl arrangement. However, the movement (with the buttons) may not work.I will try to upload a version of the bowl for the 10mm transducers soon. If possible a version that support both transducers.

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  • Asier Marzo's entry Acoustic Tractor Beam is a finalist in the Arduino Contest 2016 contest 4 months ago
  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam4 months ago
    Acoustic Tractor Beam

    They look legit, but it is always very hard to say. They may not be as powerful or the phase devitation could be high.

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  • Asier Marzo's entry Acoustic Tractor Beam is a winner in the First Time Authors Contest 2016 contest 5 months ago
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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    Dear Shlambda,The acoustic pressure may not be that strong but it will deform the surface of a balloon. In fact, if you point the tractor beam towards a container with water you will see the two focal of the Twin trap.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    Those Alibaba transducers work like a charm, they are more powerful and have less phase deviation. 500pcs + freight cost + bank fee should be (175+55+15)=245$ I am planing to release an Instructable about a directional speaker that use the same transducers. So they may come in handy later.Sorry guys, did not know that the shops would ran out of transducers.

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  • Asier Marzo's entry Acoustic Tractor Beam is a finalist in the First Time Authors Contest 2016 contest 5 months ago
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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    You are right, placing foam around the transducers could reduce secondary reflections, although in this configuration it is not a big deal.The design is optimum for 25 transducers. A larger sphere with more transducers would certainly add more power, but transducers are a little bit pricey and 25 is about the maximum that you can drive with one driver.Glad that you like the project, thanks for your comments.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    Tining the tips helps to put several wires in the same hole. Get a cable peeler otherwise it is a nightmare to do the wiring. Get a cheap oscilloscope to get the polarisation of the transducers and test the signals at each point. Good luck!!

    I have added them in the last step (They are inventor files).

    They look good, and good price also. I am still testing some Alibaba transducers that are 0.3$ units, if they work well I will put them in the description.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    They look alright, are they from Alibaba? I ordered some of those to test.

    The bowl could be the same since it is naturally focused. The code will need to change substantially: the timer1 adjusted for 25khz, the delays between OUTPUTS increased and the phases that are output changed. No worries I have plans to release more versatile boards. One easy way would be the use the code from the last steps that is much easier to change to generate 25khz.

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  • Asier Marzo's instructable Acoustic Tractor Beam's weekly stats: 5 months ago
    • Acoustic Tractor Beam
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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    Yeah, although usually the metallic ones do not work that well.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    Not at all, in fact a student is designing a handle where everything sits properly. We can upload the STL later. But I prefer the wooden since it is cheaper and faster.

    Sounds perfect, we have some related stuff. If you beam a sound wave into some sort of spiral it will rotate. Or directly Bessel beams will rotate disks of light materials.

    The previous prototypes had a signal for each transducer, so we could move the particle anywhere and even rotate it. But we wanted to simplify the project as much as possible, so having more than 4 signals would imply another driver.

    They will not work mainly because they seem designed for water, I think they are also weaker than the others, the frequency is a little bit higher and they will not fit the sockets. These ones may do the work although the metallic ones do not work as well as the plastic ones: http://www.ebay.in/itm/40KHz-Ultrasonic-Sensor-Pair-Transmitter-ZT40-Reciever-ZR40-1-Pair-/162333202789?hash=item25cbd01965:g:wc4AAOSwCGVX3PZ~

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    The shape of the bowl is kind of optimum but you are right you can get any bowl and it will work. In fact the first prototypes were made by cutting those big plastic spheres, if you can find one of about the same radious and cut it at the same hight, it should work like a charm.

    I just said 30 to have some spare ones. You can populate all the sockets to have a little bit more of strength, they will use the same signal as the row of 5 transducers on top.

    Sorry I missed the question. "why it doesn't move vertically (along the axis)." you are right looking at the twin trap or vortex is easy to see how it gets trapped laterally since particles moved from high-amplitude to low-amplitude, we call this the amplitude gradient. There is a another force that comes from velocity-gradients and that is what keeps the particle trapped vertically. If you check the Gorkov it is the second term which is as intuitive. Basically when the particle is between curved surfaces of high-itensity it will try to go to the narrowest point.

    Exactly, all the coils start at the same height and end at the same height, but they have different lengths. So when a simple planar wave enters the coils, the sound has exactly the same phase at each coil but when it exits there is the appropriate phase at each coil. Phase <=> Delay <=> Distance.

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  • Asier Marzo made the instructable Acoustic Tractor Beam5 months ago
  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    Indeed Nova, sound travels even better through water (or flesh). I am really keen on manipulating kidney stones from the exterior. But everything takes time.

    Sure, paper is free, it has some experiments and simulations http://aip.scitation.org/doi/full/10.1063/1.4972407 . In its suplemental there are also a couple of videos.

    This version can deal with expanded polystyrene, pieces of popcorn and Cheetos. If you crank it up to 30v, then small flies and similar insects. The problem is that tractor beams have pulling forces that are 30 time weaker than a traditional standing wave. You can make two of these devices place them face to face and feed the same signal into all the channels, that creates a standing wave that can levitate liquids. But no worries, we will keep releasing our different devices and software related to ultrasonics.

    Sometimes you can hear a little bit the harmonics, especially when you point it towards a non-linear material like foam. You can feel it if you modulate it to the frequency of our mechanoreceptors (200Hz I think), that is the principle behind lots of ultrasonic haptic technologies. We will try to release an instructables on that some day.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    Sorry about that, I have added some alternative links for US and UK. I will try to keep this up to date. For the lowest prices the best is to look on the internet for good offers.

    Most of the times transmitters and receivers are the same, just that receivers have a blob of silicone on the tip. You can give them a try but I remember that those metallic transducers do not work as well as the plastic ones. I think the cheapest option is to order them in Alibaba (0.3$ each) but the min order is usually 500.

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  • Asier Marzo commented on Asier Marzo's instructable Acoustic Tractor Beam5 months ago
    Acoustic Tractor Beam

    There are several transducers but they are all driven with the same signal. In the coils device it would be possible to use a single source but it is quite hard to get such a big and powerful planar source for air.

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  • Asier Marzo entered Acoustic Tractor Beam in the Sci-Fi Contest 2016 contest 5 months ago
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