Sharing some information.

Greetings to all, I built my first laminar water nozzles in 2003 and have refind them in two dozen variations since. I would like to share with anyone instrested how I created a "Knocker". I use a device called a transducer more specifically a audio transducer. A speaker is a audio transducer but, is not as efficient or ease of use as a tactile transducer. These devices are more commonly called a "Bass Shaker" you can google that and find a plethora of information. By simply attenuating the frequency supplied the effect can be subtle to dynamic and attenuated to music. PQN Audio makes a great marine waterproof audio transducer, retail is $99 and wholesale $60 US, but they are not all that hard to make. Put a couple of these in your pool and have some underwater ambient music or tell the kids to get out when there ignoring you buy staying under. I'm soon to construct another pair for the fountain I just finished at my business and will post some pictures and video of the nozzles, cutters, knockers, light and the microcontroller to run it all in action.

P4H

I've enjoyed touring this forum the skill and creativness of you all.

Hello!

Could you explain further how you make the knocker, it seems very interesting. Where do you place the shaker, inside the water? How do you drive the shaker, with a square wave of a certain frequency?

Thanks!

Hello Scarfy,

I would be glad to. Mounting the tactile is through experimentation, the variables being the size of the nozzle and the material it is constructed from. My 8" nozzles around my pool required the transducer to be placed 3/4"s of the way to the top to achieve the results I wanted " to pulse to the beat of music ". Where the very small 3" nozzles in my mothers garden required the transducers to be place on the bottom of the nozzle. Most important is to make sure the transducer is coupled to the nozzle very well to insure a good transfer of energy. Unless you have a marine grade transducer you will have to protect it from moisture, the problem with doing so is tactile transducers are not very efficient, the result when used for long continuous periods is heat, where a marine grade tactile can be cooled by the water itself. The trade-off is price, $25.00 for a decent tactile, $90.00 " Retail US " for a marine grade.
Driving the transducers can be straight forward or complex depending on what you want to achieve, I've done both. To start I built a Class D amplifier to drive the transducers only 50 watts @ 2 ohms, Class D because the are very efficient especially at lower frequencies and are very forgiving of impedance floating. On the pulse to the music side the signal starts at my pre-amp for the pools theater system then runs into input 1 of a pre-amp equalizer " little more on that in a minute " then to the class D amp. For the special effects side, that starts at the micro-controller for the special effects. I spent a weekend using my function generator, playing with different frequencies, changing there amplitude, attenuation and the symmetry of the wave form to find the most interesting dynamic effects. Once I had what i liked, I encoded them into a mp3 format and placed them on a WIG-09715 " I think that's the part # " mp3 Trigger which is tied into my Arduino micro-controller setup. I can choice from different pre-programmed effects using a wireless controller, the micro-controller then tells the LED drivers to start one of the programs and also triggers the corresponding mp3 file, that file is sent to the pre-amp EQ input 2 then to the class D amp. I use a EQ because unlike a speaker tactile transducers can have very strong resonant peaks and valleys, which causes a spreading of energy " a transducers form of distortion " causing the effect to be slow or weak, having the EQ can fix or smooth out these problems.

Think this was a little long winded but I hope it help you understand the process a little better Scarfy. Anymore Questions please feel free to ask.

P4H

Thanks for your reply!

I have some questions.
- If I understood correctly, the Transducer is mounted outside the nozzle, not inside.
- How do you make a normal transducer moisture resistant? Could I encapsulate the transducer with epoxy, leaving the moving part next to the nozzle epoxy free?
- Would it be possible to drive the Transducer with an H bridge and a square wave around 20-30hz? Or do I have to send a sin waveform?
- I believe the transducers are long lasting, am I correct?
- Could you post some pictures of the stream while under the effect of the transducer? I'm curious to see the results achieves with this creative technique.

Thank you P4H!

Any time, talking tech is yet another hobby.

-Your correct, I've never tried mounting one inside the nozzle. As the nozzle it's self is being used as the coupling device to transfer the energy it wouldn't matter if it where inside or out, out being just the most convenient.
On a budget nozzle I did, I used a old Tupperware bowl trimmed it to the curve of the nozzle and placed it over the the transducer, used industrial silicone to seal and glue it in place and have not had a problem in the 3 years it has been running.
-Audio Transducers still use a voice coil to operate, so AC current capable of a trigonometric sine function with respect to time is required to operate. They do make digital transducers but you could purchase a good car for what they cost. You could make one using very high speed stepper motor but must be balanced and made with precision, that means CNC machinery. But your limited to single frequencies and fixed phases. You can't believe most of the ratings given to most of the non-professional transducers, I have a couple under my sofa for my theater system and the lowest they can reach according to my spectrum analyser is 29.43Hz. A 6dB down sine sweep from 45Hz to 80Hz does some very cool things to the stream without disrupting it just watch the power.
-I've tried pictures they don't do a great job of showing the effect, but I will try some HD video. Picking the daughter up from college then off to vacation for the week, I'll give it a go when I get back.

P4H