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

On 27 Oct 2019 12:09:10 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

jlarkin@highlandsniptechnology.com wrote...

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.

I assume the regulator takes care of that. As speed increases, the
open-circuit voltage of the alternator goes up, maybe way up. But the
alternator is largely inductive, so above some modest speed it becomes
a variable-frequency constant-current source. I need to sort of
approximate that, and certainly current limit.





--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Sun, 27 Oct 2019 08:50:50 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Sun, 27 Oct 2019 01:30:55 -0400) it happened bitrex
user@example.net> wrote in <jY9tF.82882$hB2.34075@fx42.iad>:

On 10/26/19 11:42 AM, jlarkin@highlandsniptechnology.com wrote:
On Sat, 26 Oct 2019 03:15:19 -0700 (PDT), blocher@columbus.rr.com
wrote:

My latest assignment requires me to evaluate a power supply design that operates off of 400Hz ac power. To validate the
design I have to apply lots of signal fluctuations. These fluctuations include frequency sweeps and various voltage ramps up and
down. Abrupt frequency changes are also required. 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)

I have a gradient amplifier which is a high power op amp that is DC coupled. 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 problem I have come to think of
it as driving the unit with high power audio.

As an aside, the audio amp cannot achieve the voltages I need , but I have found a 150W transformer (2.5:1) that is good at
the frequencies I need.

Anyhow, I have matlab with simulink and using I/Q modulation against a freeruning audio source I can run my base frequency
and apply various signal 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.

I ran into one small problem....my audio output was not good. There was probably 3dB of variation in a sweep from 400-800
Hz. On a lark, I bought one of these for 10$:

https://www.amazon.com/gp/product/B07L56C28R/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

And guess what.... flat as a pancake. Absolutely perfect response (at lease where I need it).

You can use matlab and simulink as a very powerful laboratory waveform generator.

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.

https://www.dropbox.com/s/pnghjixvnxy0f3m/DSC04171.JPG?raw=1

https://www.dropbox.com/s/gz6hux8y55gs37x/DSC04173.JPG?raw=1

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

https://www.dropbox.com/s/411d7sg06s6vs62/Visio-P900_Box_6.pdf?raw=1

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.




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

https://en.audiofanzine.com/synth-rack/access-music/Virus-Rack-XL/

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

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

We have a couple of products that generate programmable sine waves in
real time, in software. A bit of periodic IRQ code runs a DDS with
sine lookup, driving an on-chip DAC. LPC1768 toy ARM.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Winfield Hill]

jlarkin@highlandsniptechnology.com wrote...

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.


--
Thanks,
- Win

 

[piglet]

On 27/10/2019 16:51, bitrex wrote:
> I hope it used like 500 LM324s.

Possibly LM124s but definitely no LM324s.

I saw early 1970s airborne controllers use many JANTX uA748 (derivative
of uA741) - you got something against old IC op-amps?

piglet

 

[bitrex]

On 10/27/19 5:34 PM, piglet wrote:

On 27/10/2019 16:51, bitrex wrote:
I hope it used like 500 LM324s.

Possibly LM124s but definitely no LM324s.

I saw early 1970s airborne controllers use many JANTX uA748 (derivative
of uA741) - you got something against old IC op-amps?

piglet

Nah! the LM324 is probably one of the most useful
if-it-aint-broke-don't-fix-it quad op amp ever made. For an analog
computer where you're working with frequencies in the 100s of Hz why not?

 

[Jan Panteltje]

On a sunny day (Sun, 27 Oct 2019 12:10:00 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in

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

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

We have a couple of products that generate programmable sine waves in
real time, in software. A bit of periodic IRQ code runs a DDS with
sine lookup, driving an on-chip DAC. LPC1768 toy ARM.

Exactly, the way to go!
Long time ago I wrote some Verilog for my Xilinx FPGA board to send user defined waveforms
8 bits analog video R2R DAC test patterns.

I was thinking for this application I would not even use .wav format
but just use raw,
Most Linux audio utilities can play that if you specify sample-rate and format,
specifically look up
play and sox
aplay

And then use 'cat' to put together pieces of signal you made in C.
cat 100Hz transient 110Hz 100Hz_amplitude_drop > test_signal.raw

Example bash code that uses aplay to play raw format read from rtl_sdr :
rtl_fm -d 0 -N -f $frequency -p 46.000000 -r 24k -l $squelch -g 49.599998 | aplay -t raw -r 24000 -f S16_LE --buffer-size 10240 -c 1 -D default -
So there is a whole NBFM VHF radio receiver in one line...


so then
cat test_signal.raw | aplay -t raw -r 24000 -f S16_LE --buffer-size 10240 -c 1 -D default -

Or shorter in one go ;-)
cat 100Hz transient 110Hz 100Hz_amplitude_drop | aplay -t raw -r 24000 -f S16_LE --buffer-size 10240 -c 1 -D default -

Example OK!
But then I am .. sometimes I edit video with 'dd', successive approximation is your friend.
Takes a few minutes.. just to get start and end or get rid of commercials from movies recorded from satellite.

If you are a microsoft purist and must use wav plenty of simple Linux utilities for that, some written by me ..

But wave format sucks for this sort of thing as it requires a header,
not needed if you know hat you are doing, and then you can also play with the speed etc.
And microsoft is now a security risk in the EU.

 

[Jan Panteltje]

On a sunny day (Sun, 27 Oct 2019 15:39:23 -0400) it happened bitrex
<user@example.net> wrote in <LnmtF.52868$Ku2.3302@fx41.iad>:

An 8 bit AVR or PIC one guy can fully understand. A modern x86 processor
system is too complex for any one person to understand all of, not even
the teams that built them.

Strange.. its is just an other processor to me
In those olden days we programmed the 386 in asm, my boss at that time was really into that
would sit next to me an we coded.
One day I started designing using 8051 and what was it 8047 with build in EPROM
I think it was, embedded and in asm, that was too much and he then required everybody to learn C
So we got C lessons from some programmer, exactly 3 hours IIR
I have Kernighan and Ritchie..
But a lot of C programming tricks I learned from a magazine: Dr Dobbs.

A data structure that wraps a dynamic array like a std::vector sure
makes life easier.

Sounds like Cplushplush, a crime against humanity!

For the rest:
See my reply to John Larkin


Look up the code for this newsreader I wrote and use now, been using it since the late 1990ties;
http://panteltje.com/panteltje/newsflex/index.html
it is K&R C with linked lists.

And it has a database that goes all the way back..
whatever one wrote that was interesting enough to me to click 'lock' is in it,
including what I wrote.. From many many Usenet groups...

Just a few hundred kbytes size, GUI,,,, ;-)
No bloat.

 

On Mon, 28 Oct 2019 08:04:58 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Sun, 27 Oct 2019 15:39:23 -0400) it happened bitrex
user@example.net> wrote in <LnmtF.52868$Ku2.3302@fx41.iad>:

An 8 bit AVR or PIC one guy can fully understand. A modern x86 processor
system is too complex for any one person to understand all of, not even
the teams that built them.

Strange.. its is just an other processor to me
In those olden days we programmed the 386 in asm, my boss at that time was really into that
would sit next to me an we coded.
One day I started designing using 8051 and what was it 8047 with build in EPROM
I think it was, embedded and in asm, that was too much and he then required everybody to learn C
So we got C lessons from some programmer, exactly 3 hours IIR
I have Kernighan and Ritchie..
But a lot of C programming tricks I learned from a magazine: Dr Dobbs.

A data structure that wraps a dynamic array like a std::vector sure
makes life easier.

Sounds like Cplushplush, a crime against humanity!

Why do anything in plain sight, when you can hide it behind a few
levels of abstraction?



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[bitrex]

On 10/28/19 11:36 AM, jlarkin@highlandsniptechnology.com wrote:

On Mon, 28 Oct 2019 08:04:58 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Sun, 27 Oct 2019 15:39:23 -0400) it happened bitrex
user@example.net> wrote in <LnmtF.52868$Ku2.3302@fx41.iad>:

An 8 bit AVR or PIC one guy can fully understand. A modern x86 processor
system is too complex for any one person to understand all of, not even
the teams that built them.

Strange.. its is just an other processor to me
In those olden days we programmed the 386 in asm, my boss at that time was really into that
would sit next to me an we coded.
One day I started designing using 8051 and what was it 8047 with build in EPROM
I think it was, embedded and in asm, that was too much and he then required everybody to learn C
So we got C lessons from some programmer, exactly 3 hours IIR
I have Kernighan and Ritchie..
But a lot of C programming tricks I learned from a magazine: Dr Dobbs.

A data structure that wraps a dynamic array like a std::vector sure
makes life easier.

Sounds like Cplushplush, a crime against humanity!

Why do anything in plain sight, when you can hide it behind a few
levels of abstraction?

why use ICs when you could build everything from discrete transistors,
or harvest sand from the beach and manufacture your own vacuum tube
envelopes with a kiln

 

[Jan Panteltje]

On a sunny day (Mon, 28 Oct 2019 12:16:45 -0400) it happened bitrex
<user@example.net> wrote in <NvEtF.27902$kV2.12798@fx22.iad>:

On 10/28/19 11:36 AM, jlarkin@highlandsniptechnology.com wrote:
On Mon, 28 Oct 2019 08:04:58 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Sun, 27 Oct 2019 15:39:23 -0400) it happened bitrex
user@example.net> wrote in <LnmtF.52868$Ku2.3302@fx41.iad>:

An 8 bit AVR or PIC one guy can fully understand. A modern x86 processor
system is too complex for any one person to understand all of, not even
the teams that built them.

Strange.. its is just an other processor to me
In those olden days we programmed the 386 in asm, my boss at that time was really into that
would sit next to me an we coded.
One day I started designing using 8051 and what was it 8047 with build in EPROM
I think it was, embedded and in asm, that was too much and he then required everybody to learn C
So we got C lessons from some programmer, exactly 3 hours IIR
I have Kernighan and Ritchie..
But a lot of C programming tricks I learned from a magazine: Dr Dobbs.

A data structure that wraps a dynamic array like a std::vector sure
makes life easier.

Sounds like Cplushplush, a crime against humanity!

Why do anything in plain sight, when you can hide it behind a few
levels of abstraction?




why use ICs when you could build everything from discrete transistors,
or harvest sand from the beach and manufacture your own vacuum tube
envelopes with a kiln

That is what you do by typing :: a trillion times for no reason at all.
And computers do not work with 'objects' but work sequential.