Mar 17, 2025
Doing more development on the non-linear music genrator
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Doing more development on the non-linear music genrator
How to Hide a Profound secret Camera
How toward Leather a Secret Telephoto lens <\p>
The video register machine, also know as the spy burning glass, is a good device; admitting that its functioning is additionally its inefficacy. Each camera is lens dependent, in order to pick up visual information, more the powerful lens higher the program of action quality, so what happen if the lens someway turn into conciliate? A camera nictitating membrane perhaps wrecked, enclosed or all right be in an mistimed position to capture the requisite exertion. Think how numerous times we have attempt to take an clear still image or video only to have somebody or something wend into frame and rest the shot? Imagine this irksome happenstance happening when grueling to capture activity which might give sustaining or grave proof in a prosecution case and it's not a clear image. Add to this mode the recoil of capturing stuff as constituent of a unobserved operation i.e. floored filming with secret cameras; one is fit to clearly recognize a miserable popular belief with both the expert and amateur rummager.<\p>
Camera dugout best place<\p>
On publicity respecting lens hindrance, an incomplete or blanked out screenshot is owning by to no without generous supporting confirmation, for monition, that gave by a sound recorder. This absence on reinforcement exhibit could conceivably enlist about the misfortune of fertile and costly asset or even lose a once-just chance headed for catch ranking knowledge. The Camera's innate mark for cash is expanded exponentially when it incorporates a pipe roll apparatus. When all is voiceful in done, this is since a vital sound or voice tin-whistle keeps on operating absolutely when the visual viability of the machine has been traded off. This can bring about the substantial weaving apropos of authoritarian lip proof. Even out of a pessimistic mental outlook, question markers throne give signs into ranges with regard to further examination, along these lines benevolentness a no mean balustrade. Historic point cases drop been carried to court and won, on a reckoning of of the UK unaffected respect at last tolerating sound recordings as legitimized confirmation. Criminal feelings and barely sufficient sentences have emulated and this raises the worth of the viva voce basset oboe as a crucial bit relative to spyware pack. <\p>
Putting it for authentic recording <\p>
Whatever pretense the creek recorder comes in, today's dream-built sound catch engineering can for the most part be depended upon to spine sensible sound tracks. Where rend goodly generation is obliged, close consideration ought so as to persist paid to the specialized picayune of items. Watchful examination make a bequest help to distinguish the convenient devices for the work under control and obviously, at whatever time used picking your allied varying media or sound justice of assize is lifetime well not new. Azygous relate pregnant trip with your new supplies could see your take chances gave type lice a hundredfold or more.<\p>
Sound Generation is Effective Silo Cleaning Method
Based in Malvern, Pennsylvania, Airmatic Inc. is a woman-owned distributor of industrial machinery and equipment. Among other services, Airmatic Inc. provides silo cleaning throughout the Mid-Atlantic states and New England. The company offers several silo cleaning options, including sound generation. For one client, a power generation station, the company had originally anticipating mechanically scrubbing three silos that had caked material clinging to their walls. However, the silo’s location and roof configurations made mechanical cleaning difficult and less effective. Instead, the company used high-energy sonic horns to generate sounds that shook particles loose from silo walls. After dislodging the build-up, the company used gravity feed to extract multiple tons of material from each silo. When silo cleaning becomes necessary, sonic horns offer the advantage of efficient cleanout without requiring personnel to enter the silos. Companies would benefit from consulting with silo cleaning experts to learn if sound generation is the right choice for their needs. In addition, sound generation can be used to clean other types of vessels, including bins, bunkers, chimneys, and rail cars.
PWM + Sound Generation Conversation III
So the goal of the discussion was really to figure out how to use PWM and an RC filter to get waveforms such as sawtooth, triangle, and even sine.
So I asked a few things for clarification:
To bring code PWM into a wave - would it be like you'd code to ramp up duty cycle to a certain peak, then ramp down duty cycle over a period of time for triangle waveform? Or for sinewave it'd be a constant ramping up then ramping down at the same rate.
Mgburr: The sawtooth can be done the same way, but the difference would be the sine has an even back pressure on the vessels, where the sawtooth has a level to reach and then breaches. Here's a fairly simple look at how PWM is created, you have a defined frequency(repetition time) and a modulating value mixed together. fab.cba.mit.edu/classes/MIT/961.04/topics/pwm.pdf
And then I ask for more clarification: To code a triangle - assuming one cycle is 2seconds...I'd write something like....ramp dutycycle from 0 to 2 seconds over 1 second....then ramp duty cycle from 2 to 0 over 3 seconds?
I think this might mean I need to learn how to code the four typical waveforms involved in sound generation.
Oh and there are some really nice examples in here as well: http://www.wpi.edu/Pubs/E-project/Available/E-project-042711-190851/unrestricted/PWM_Techniques_final.pdf
@atdiy/@tymkrs
PWM + Sound Generation Conversation II
So here're some basic definitions I think need to be covered (which we have in previous posts, but let's do it again for posterity's sake).
Duty Cycle = Ratio of time on to overall time
RC Filter = This is a low pass filter made with a resistor and capacitor. Depending on what you choose for these components it allows for charging of the capacitor and discharging of the capacitor. When the PWM signal from your MCU goes through this filter, you get an analog wave on the other side.
Notes on the RC Filter courtesy of mgburr and raivisr:
So before the RC filter, no matter the frequency of the pulse widths (how often pwm signal repeats), duty cycle determines the effective voltage. That is to say, 90% voltage from 1 second out to 10 years is still 90% of voltage.
Once you put them THROUGH the RC filter, then the rate of charge and discharge in this filter determines how much is let through. If you set up the charge/discharge to be longer than the pulses, then it's slower to build up and slower to reduce. If the charge/discharge is less than the smallest duty cycle, then you get the straight effective voltage through.
The only time the number of repetitive cycles comes into play is if the charge/discharge time is slow enough to not completely discharge before the next pulse starts. The effective voltage out will still never be more than the input source.
So in a 0-5v pulse, @90% duty is still only 4.5 and after the 4.5 is reached, the rate of charging to 5v is much slower. It may take 20 cycles to reach the 4.5 but 4.5-5v could take 80-90 cycles. Which is why it's important to know what the RC time is, in order to properly gauge what pulse widths will give you the best shape.
Varying the PW is like taking the DC power source and slowly changing the output voltage on the dial up and down. The RC circuit takes those changes and smooths them out to form a more even sine wave.
And an example:
The simple on/off PWM signal modulating a carrier wave:
After putting this signal through a low pass filter (RC circuit):
You see the wave superimposed on the original PWM signal.
And next, some of my thoughts/clarifications.
@atdiy/@tymkrs
PWM + Sound Generation Conversation I
Alright. So again, this was a topic discussed in the most recent First Spin and it was how using PWM would allow for sound generation. Somehow you can code little ons and offs to become different types of waves. Thanks to @Rednaxela @insurgent @raivisr and @mgburr for their immense help and time in explaining this to me as well as to the original explainers @RoyEltham and @whixr.
Rednaxela: As far as the PWM for sound goes, all the PWM is used for is creating an analog voltage level. After that, it can be considered essentially no different than having an analog output and outputting a waveform
RaivisR: Atdiy, think of sound wave as having value on y axis from 0 to say 255 in case of 8 bit resolution and pwm having time from 0 to 255
Atdiy: So the way my brain is imagining PWM and sound waves is like calculus. And using a lot of boxes along the wave to form the sound wave (whether sawtooth or sine). http://www2.math-4-u.com/child/biseki/graph2.gif <-- like that
Rednaxela: Well, all of the 'boxes' are the same height with a pwm signal. It's the density of them that defines the analog level after the filter. Also if you plot the waveform you want, scaled so the y axis is from 0 to 1... the y axis value is the duty cycle you want at that moment in time.
RaivisR: or in simplistic terms, the longer on pulse is, the higher voltage the cap charges. The on pulse is converted to voltage by the rc circuit. Think of sine wave plotted on x and y axis and now divide it in regular intervals on x axis. Then measure y value for each of those points. And then, to reconstruct your sine, you need to output the same values at the same rate you just divided your x axis.
insurgent: The filters after the PWM determine the way that the spiky digital signal is "integrated" into some desired analog signal.
mgburr: Atdiy, try to imagine it like this: A heart beat has a defined repetition time. if you change the length of the valve openings during that time to increase, then the heart pushes more blood(power). If you shorten the valve times, and increase the gap between the next start you reduce blood flow. It's like having the heart on a pacemaker that gives a clockwork start time, you have to know what pressure you will be up against(RC) time. and vary the on times accordingly.
A few months ago we talked about effective voltage for the power supply. The increased duty cycle (longer time on) results in the "effective voltage" being higher. Lower duty cycle (shorter time on) lower effective voltage. So if you have 5ms on, 5 ms off, duty cycle is 50%. If you have 5v it would have an effective voltage of 2.5. 7ms on, 3 ms off would be closer to 3.5 because duty cycle would be about 75%.
Rednaxela: If you plot the waveform you want, scaled so the y axis is from 0 to 1... the y axis value is the duty cycle you want at that moment in time.
Next - some more conversation!
@atdiy/@tymkrs
LIQUID~DO. Sound generation from chemical process.