Amplifier for portable transducer speaker

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bsg2113
 
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Amplifier for portable transducer speaker

Post by bsg2113 »

Hi crew!

I am a building novis and want to start out with a project to build something that I would want to use. I want to build a portable transducer speaker so that I can easily turn any surface into a speaker.

I saw that the medium surface transducer requires an amplifier to get the signal strong enough. The options I am looking at for the amplifier are the Stereo 2.3 or 3.7 W Class D amps, or the stereo 20W class D.

Do the first two options require an arduino to control them/their output or could they function autonomously? I like their form factor, but want to make sure that I understand their requirements.

Thank you. And I would love any suggestions people have!!

Cheers,
Ben

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adafruit_support_mike
 
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Re: Amplifier for portable transducer speaker

Post by adafruit_support_mike »

The 2.8W and 3.7W amplifiers are standalone devices.. the only thing a microcontroller could do is toggle the 'shutdown' pins. The 20W amp also works as a standalone unit, but you can set the volume digitally too.

Overall, the 3.7W unit seems like the best match for the transducer, which is rated as 4 ohms and 3 Watts. The 2.8W amplifier isn't quite strong enough, and the 20W amp is overkill.

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Gibsonjs
 
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Re: Amplifier for portable transducer speaker

Post by Gibsonjs »

As with the previous users post, I could use some help understanding what I'd need for a project that I'd like to do.

Background:
I'd like to use the medium (or tiny - which I can't find online at the moment from your store) surface transducer to vibrate a variety of plant surfaces. Currently all our outputs are in voltage (obviously) but we record and calibrate these playback transducers through the use of laser Doppler vibrometer, which measures velocity. We calibrate the output of these transducers in velocity using DAQ's from National Instruments (NI) controlled through custom MatLab programs. The NI DAQ is limited to a + or - 10V range and we sometimes have issues reaching velocities higher then 8mm/s in that range. Thus, we'd like to add an amplifier to the system to achieve higher velocities.

Since experimental designs can be complicated and take up a lot of space (cables, etc.) we'd like the amplifier solution to be small and compact and if possible right inline with the surface transducer. I have no experience with the small amplifiers you offer but from everything I've seen commercially available your solutions seem much more inline with what we'd like to accomplish. What we need to do something like: NI DAQ output, to amplifier, to surface transducer? What items would I have to order?

Any suggestions would be much appreciated - Cheers,

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adafruit_support_mike
 
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Re: Amplifier for portable transducer speaker

Post by adafruit_support_mike »

8mm/s isn't very fast, especially for a transducer being driven by a 10v supply.

How much current does your DAQ put out? That may be your limiting factor.

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Gibsonjs
 
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Re: Amplifier for portable transducer speaker

Post by Gibsonjs »

Thanks for the reply, The DAQ puts out + or - 10V / channel. We are eventually going to have 16 transducers connected the DAQ and we would like to have a velocity range from ~1mm/s up to around 30mm/s. Thoughts?

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adafruit_support_mike
 
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Re: Amplifier for portable transducer speaker

Post by adafruit_support_mike »

We are eventually going to have 16 transducers connected the DAQ and we would like to have a velocity range from ~1mm/s up to around 30mm/s. Thoughts?
That's awfully slow for audio frequencies.

If we assume a speaker cone moves 1mm between its extreme positions (which is a fairly short throw), playing a 1kHz sine wave would move the cone through a total distance of 2000mm per second, and the peak velocity of the cone would be around 6.3m/s.

For the speeds you want, a servo or stepper motor would probably give you better performance.

How much throw do you need?

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Gibsonjs
 
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Re: Amplifier for portable transducer speaker

Post by Gibsonjs »

Thank you for the response.

I'm not sure what you mean by throw, but I am going to guess you are referring to what we are trying to move with the transducer. For this current project we are attaching very light leaves to the transducer. With the medium surface transducer we were able to get a range of 1mm/s up to 9mm/s BANNED (peak not RMS) before we'd hit the cap of our DAQ which is + or - 10V. Hence we thought that by adding an amplifier we could push the transducer beyond 9mm/s. In actuality it is likely we'd never need to go above 9mm/s, but "never" is a dangerous word in biology. Thoughts?

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adafruit_support_bill
 
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Re: Amplifier for portable transducer speaker

Post by adafruit_support_bill »

I'm not sure what you mean by throw
By "throw", he means the total distance moved by the transducer. I'm assuming that the distance you need to move is fairly short since these transducers have a fairly limited range of motion.

We don't know the specifications for your DAC, but most are not designed to source a lot of current. An amplifier would likely be able to provide more current to the voice-coil and achieve faster motion.

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Gibsonjs
 
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Re: Amplifier for portable transducer speaker

Post by Gibsonjs »

Correct, the total distances are very small (in micrometers).

I envision a custom built box with an Input and output (RJ58 - 50Ohm connectors), with either one channel/box, or with all 16 channels in one box. Do you have any suggestions on an AMP(s) we can use for the Medium Surface Transducer for this application?

Thanks...

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adafruit_support_bill
 
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Re: Amplifier for portable transducer speaker

Post by adafruit_support_bill »

Making the assumption that the your performance now is limited by the current sourcing capabilities of your existing DAC, you probably don't need too much additional amplification. These little mono amp modules would probably do the job.: https://www.adafruit.com/products/2130

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