400Hz 115V ac power testing - Matlab/simulink to the rescue

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Crown M600s were never sold as audio amps, cos it's mono

- so always a lab thing.

... Phil

Those are exactly what I am using. It is an incredible unit. We had always used it for our DC testing.

We have a rackmount Peavey 800 watt amp and some transformers to generate 120/240 VAC and high current/low voltages (to drive CTs) at various frequencies. Works fine. The Peavey had a lot of phase shift at 60 Hz, so we beefed up some coupling caps.

I'm now designing a 3-phase AC power source to simulate aircraft power. We're using 500 watt TI h-bridge chips and custom toroidal transfomers.

We were talking here about cooling the class-D chips. I think we'll put them on the bottom of the board, with a heat sink and a fan real close.

My mechanical designer is on vacation in the Azores, so I had to hack the box layout in Visio.

Visio is terrible for things like this. I'm going to force myself to learn Fusion.

You have made me think about hanging some DRAM on the FPGA and allowing complex waveforms to be stored and generated, not just sine waves. Premium ver$ion.

I think I'll just tie-wrap the fan to the board and solder its leads to a couple of vias.

If it's just for the audio band you could also use a digital synthesizer. Like the kind for making music with. like:

the digital units are accurate to fractions of a Hz and you can define your own tunings and tone sequences. A lot of modern pop music is all "frequency sweeps" and "abrupt frequency changes" anyway.

Matlab/Simulink is over 2 grand for a commercial license, that rack box above cost about 500 bucks second-hand probably

On a sunny day (Sun, 27 Oct 2019 01:30:55 -0400) it happened bitrex wrote in :

It is not so hard to write some C code and write samples to a wave file.

operates off of 400Hz ac power. To validate the design I have to apply lot s of signal fluctuations. These fluctuations include frequency sweeps and various voltage ramps up and down. Abrupt frequency changes are also requi red. Most of these waveforms are not available on function generators and are not even realizable on arbitrary waveform generators (at least I could not figure out how to easily create them)

led. It turns out this is a high powered audio amp that is dc coupled (it was made by crown audio and relabeled by picker ). After rethinking this p roblem I have come to think of it as driving the unit with high power audio .

ve found a 150W transformer (2.5:1) that is good at the frequencies I need.

freeruning audio source I can run my base frequency and apply various signa l transformations and create nearly every specified waveform. I then play them out of the audio port of the computer and into a simple op amp then to my gradient amplifier.

probably 3dB of variation in a sweep from 400-800 Hz. On a lark, I bought one of these for 10$:

e_o03_s00?ie=UTF8&psc=1

ease where I need it).

enerator.

Are you designing a 3 phase supply that can also impose the various DO-160 perturbations on the signal?

t operates off of 400Hz ac power. To validate the design I have to apply l ots of signal fluctuations. These fluctuations include frequency sweeps an d various voltage ramps up and down. Abrupt frequency changes are also req uired. Most of these waveforms are not available on function generators an d are not even realizable on arbitrary waveform generators (at least I coul d not figure out how to easily create them)

upled. It turns out this is a high powered audio amp that is dc coupled (i t was made by crown audio and relabeled by picker ). After rethinking this problem I have come to think of it as driving the unit with high power aud io.

have found a 150W transformer (2.5:1) that is good at the frequencies I nee d.

a freeruning audio source I can run my base frequency and apply various sig nal transformations and create nearly every specified waveform. I then pla y them out of the audio port of the computer and into a simple op amp then to my gradient amplifier.

as probably 3dB of variation in a sweep from 400-800 Hz. On a lark, I boug ht one of these for 10$:

lease where I need it).

generator.

Here is an example of a signal to generate: The signal free runs at 360Hz. at a moment of you choosing the signal ramp s down to zero volts in 20 msec and stays at 0V for 80 msec. The signal th en ramps up to 115V in 20 msec at 800 Hz. Afterwords the signal continues to play at 800 Hz. wave files can sort of work but you do not get to time when to introduce the transient, which is much better.

On a sunny day (Sun, 27 Oct 2019 02:59:44 -0700 (PDT)) it happened snipped-for-privacy@columbus.rr.com wrote in :

Bull, you can switch amplitude at 1/fsample.

The immediate application is simulating a 3-phase PM alternator that powers a FADEC. If I can make the box more general, I should, and maybe sell some more. The key to simulating the alternator is to be able to program complex impedances as well as voltage and frequency.

I don't think we'll try to do the full DO-160 thing, with transients and such.

We plan to do polyphase DDS waveform generation in an FPGA. We have done that many times before and this will be routine. The analog outputs will be from a quad 16-bit SPI DAC. Again routine.

Most of our problems here are mechanical/packaging/cooling. And getting the customer to give us the info we need, which is why this is going so slow.

This air flow looks pretty good, small fans tie-wrapped to the bottoms of the amp boards and one overall inlet fan on the side.

When my SolidWorks guy gets back, he can make it all work.

Yeah that's not hard to do. WAV-file writing though is one of those exercises that proves a point about C or perhaps coding in general - Ask any average programmer to write a C program that can write some arbitrary data in an array to a .wav format file in C it's a less-than-one-afternoon job.

however ask a programmer to write an API that opens _all_ common .wav file formats (the data can be e.g. floating point or signed int, mono or stereo, interleaved or not, 16 bit, 24 bit, etc.), allows the sample data to be easily dumped to an appropriately-sized array or arrays in memory for manipulating, and then easily allows arbitrary edited data to be written out to a new file of the same format you started with, or perhaps a different format. And performs this task correctly with any .wav file you throw at it in the usual they often come in.

This isn't an unreasonable task to want to do, and superficially the .wav file format isn't particularly complex it's just a text header and some formatted PCM data afterwards, it's not even compressed. If you wanted to even say start to write an audio-editing application in C and didn't have a library to do this off-the-shelf you'd have to do it yourself.

How long would you estimate that job would take and make sure the result is bug-free, in C, for the "average programmer"?

Can you show a screencap of how that's set up in Simulink?

It could likely be done with some kind of audio production hardware/software, or a .wav editing suite, but from your description it does sound like it's faster to put together the test suite in Simulink than either of those. Surely than writing C code oneself to do it!

I watched a few videos about FADEC, fascinating! John, I will say this, you are having entirely too much fun.

"Full authority analogue control was used in the 1960s and introduced as a component of the Rolls-Royce/Snecma Olympus 593 engine of the supersonic transport aircraft Concorde."

I hope it used like 500 LM324s.

On a sunny day (Sun, 27 Oct 2019 11:30:12 -0400) it happened bitrex wrote in :

Most programming is not a less than 1 afternoon job. As I have done all that stuff in C and soem of it is actually on my website and then I am also going back to the eighties about doing it. I do not see the problem. The problem arises when you start tinkering with a lot of bloated libraries that may or may not do what you want and shield you from basic hardware. I did sound for the IBM PC when most never even heard about an IBM PC. Was part of my job (announcement system, spoke from wave tables). Even worse some did it in X86 asm.

You do know that 'hello world' in asm is only a few bytes?

To isolate so called programmers from the hardware is evil, leads to bloat, and avoids them understanding what really happens. The total learning time of all the bloated programs and libraries is then greater than you reading up on the wave format and writing some simple code to do whatyouwannado.

That said I have been coding 12 hours a day at least for the last few days rewriting Raspberry Pi4 code now I have a media system, satellite receiver, new desktop, networked video, several browsers, extra storage etc.. its is hard work in a way, but also rewarding one it all works.

The man wants signals to his amplifier to test things. Stay with what is needed and get it done. Write it in any language you want, but C is the best for those things IMO.

FAAEC ?

Both of us are fortunate to be electronic dilettantes. We get to play with all sorts of science and technology for a while, see wild stuff and design electronics for it and be heroes, and move on in a few months without making any of that our careers.

My customer is threatening to send me a FADEC, which I have no use for. What I really want is an alternator. I want to chuck it into a milling machine and spin it up and measure things. I have tried to buy a used/junker alternator from aircraft repair companies, no luck so far. The ones on small planes are usually modified excited-field car types.

The FADECs initially power up off aircraft 24 volts DC. Once the engine fires up, they get their power off a private PM alternator geared to one of the fans.

Alternators are often shunt regulated, ie shorted, so my source has to tolerate that, and present about the right impedances and load line.

You also must make sure your source can't damage the FADEC.