The appearent conflict here is in the definition of real time.
For the video capture application we only need to keep up with the
average data rate and if the system stops reading data for a few tens
of milliseconds and lets it buffer in the capture hardware then it is
OK because nothing is lost.
SDR isn't as taxing as you think. I'm running 4 of those rtlsdr type dongles on
an A8-cortex. Granted under linux, but this is a single core Arm.
The multimedia versions of linux don't get much press these days since the
kernel itself now is rather low latency. But if you google linux
albertson.ch...@gmail.com said:
For the video capture application we only need to keep up with the average
data rate and if the system stops reading data for a few tens of
milliseconds and lets it buffer in the capture hardware then it is OK
because nothing is lost. The only criteria for
Good explanation. I guessed, since the list is time nuts I assumed
real time in reference to an OS would be understood. :) My bad.
Because windows is not a real time operating system (RTOS), I lack
seeing the purpose in getting the windows clock synchronized to within
microseconds or
The timing/logging of events can benefit from precise time, even if the
processing of such data is not real time. MLAT/TDOA for example. But I believe
stock trading uses precise timing in order to queue orders.
On my list of sdr hacks is a radio interferometer. Precise event timing there
would
On Wed, Mar 27, 2013 at 9:46 AM, Dan Kemppainen d...@irtelemetrics.comwrote:
As for timing things on windows, check out how to read the performance
counters in windows. I believe these are QueryPerformanceCounter and
QueryPerformanceFrequency in kernel32. In most modern systems these should
orin.e...@gmail.com said:
Then all bets are off if you have a CPU that runs at variable speed if you
want the result to be actual time.
I think that got fixed on newer CPU chips. I don't know when.
Another interesting problem in that area is that the temperature changes with
the CPU load.
On 3/27/2013 2:54 PM, time-nuts-requ...@febo.com wrote:
Then all bets are off if you have a CPU that runs at variable speed if you
want the result to be actual time.
I think that got fixed on newer CPU chips. I don't know when.
Another interesting problem in that area is that the temperature
Well, I can come up with something topical, read on. :)
I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of
course, I had to buy it.
What I got was the yaw-rate gyro package from a Northwest Airlines DC-10
that was stripped for parts around 2000. The gyro included the pull tag
How about one of those 2kw car stereo amps with a 555 input tone ?
--- On Wed, 3/27/13, Bill Ezell w...@quackers.net wrote:
From: Bill Ezell w...@quackers.net
Subject: [time-nuts] OT - DC-10 gyros
To: time-nuts@febo.com
Date: Wednesday, March 27, 2013, 1:40 PM
Well, I can come up with
Watch eBay for a small static inverter. I got an Abbott one for under $50.
It takes 28 VDC and puts out 115VAC 400 Hz.
-John
===
How about one of those 2kw car stereo amps with a 555 input tone ?
--- On Wed, 3/27/13, Bill Ezell w...@quackers.net wrote:
From: Bill Ezell
Great to know there's someone around who loves complex electro-mechanical
systems! I thought the population had dropped to zero!
Regards,
Lee
- Original Message -
From: Bill Ezell w...@quackers.net
To: time-nuts@febo.com
Sent: Wednesday, March 27, 2013 2:40 PM
Subject: [time-nuts]
For thumbsized gyros, the power-drain is probably very slight.
A class-D may or may not be a good idea, I'd worry about the
stability faced with a weird load like motors.
That said, I have been toturing one of these to no end, and
not managed to kill it yet:
Hi
The first question is how much 400 Hz power do I need?. Without knowing if
it's tens of amps (no, it's not…) or a tenth of an amp, it's a bit though to
decide how much to spend on the solution.
Eight ohms at 28 volts would be just a bit under 4 amps. It's also right at 100
watts. I'd be
Good points, Bob. At 400 Hz and low power, I'd think a decent LC low-pass
filter would be feasible for cleaning up any trash on the inverter output.
LC to minimize the series losses and provide a bit of peaking at 400 Hz.
Tom Holmes, N8ZM
Tipp City, OH
EM79
-Original Message-
From:
I neglected to mention that. The DC resistance of the motor windings is
roughly 200 ohms. I estimate the power draw is 2 watts. Haven't
measured the inductance.
I probably could just use some FETs and build a simple class-B amp. The
sine wave doesn't have to be absolutely pure. Frequency
Yeah I'd join a gyro-nuts group. I have a shelf full of weird gyros, a stable
platform, other gyro stuff. I made a little power supply to make 28 volts 3
phase 400 Hz, found it in an app note, for running a set of three tiny rate
gyros I picked up. I'll go dig it out and let you know.
An appropriate (but small) Group already exists:
http://tech.groups.yahoo.com/group/Aerospace_Hardware_Collectors_Group/
-John
===
Yeah I'd join a gyro-nuts group. I have a shelf full of weird gyros, a
stable
platform, other gyro stuff. I made a little power supply to
Hi
For that kind of power, I'd dig out an audio transformer and drive it with
something like an LM-380.
Bob
On Mar 27, 2013, at 6:59 PM, Bill Ezell w...@quackers.net wrote:
I neglected to mention that. The DC resistance of the motor windings is
roughly 200 ohms. I estimate the power draw
The circuit I built used a ULN3751Z (TO-220) amplifier chip and some capacitors
to create the phase shifts for making 3 phase. Very simple oscillator circuit.
Haven't found the docs yet but found the unit itself.
On 3/27/2013 6:59 PM, Bill Ezell wrote:
I neglected to mention that. The DC
Orin writes:
If you use those, you have to lock the thread you are timing to one
CPU/Core as the performance counters are per CPU/Core and can get
out of step. Or you can force your thread onto one CPU for the
QueryPerformanceCounter call. This seems to be a bad idea to me as
it would add an
Is this part of an HSI (horizontal situation indicator), ADI (attitude
director indicator), INS (inertial navigation system), or autopilot? Are
the bearings dust?
Sounds like fun to play with though. What do you plan to do with it?
Joe
-Original Message-
From:
Bill Ezell;
Your Gyro may require 3 phase, 400 cps, 28 vac, Sine wave.
A simple Buffered Phase Shift Oscillator for 400 cps can create the Sine Wave.
https://www.circuitlab.com/circuit/h6v28g/buffered-phase-shift-oscillator/https://www.circuitlab.com/circuit/bakd83/phase-shift-oscillator-ii/You
Hi
If three phase is actually needed, I'd suggest something like a cheap PIC with
three PWM outputs. Fairly simple R/C's on the outputs should be plenty good
enough to filter out any crud. Good frequency stability / accurate phase shift
/ cheap. What's not to like ….
Bob
On Mar 27, 2013, at
I have a little dynamotor somewhere which makes 3 phase 400 Hz. Tiny little
thing! Only puts out like 15 VA, and not very noisy either. IIRC is was called
an Instrument inverter
On 3/27/2013 9:55 PM, Bob Camp wrote:
Hi
If three phase is actually needed, I'd suggest something like a cheap
On 3/27/13 3:20 PM, Bob Camp wrote:
Eight ohms at 28 volts would be just a bit under 4 amps. It's also
right at 100 watts. I'd be very surprised it you need anywhere near
that much current. You probably want a pure sine wave to keep
everything happy. A lot of the simple inverters are sort of
It was almost certainly for powering a WWII vintage fluxgate compass system.
-John
==
I have a little dynamotor somewhere which makes 3 phase 400 Hz. Tiny
little
thing! Only puts out like 15 VA, and not very noisy either. IIRC is was
called
an Instrument inverter
On
On Mar 27, 2013, at 22:54, Jim Lux jim...@earthlink.net wrote:
On 3/27/13 3:20 PM, Bob Camp wrote:
Of course, for the more mechanically inclined.. what about a big flywheel
driving an alternator. You might be able to rejigger a car alternator. I
don't recall how many poles they
If you need good 3 phase 400 Hz you can get a VFD which goes up that high and
program it to just sit there making 400 Hz.
On 3/27/2013 11:16 PM, bownes wrote:
On Mar 27, 2013, at 22:54, Jim Lux jim...@earthlink.net wrote:
On 3/27/13 3:20 PM, Bob Camp wrote:
Of course, for the more
Crikey - an alternator?
Automotive alternators typically have 6 poles, which delivers
60 Hz at 1200 RPM. You would need to go to 8000 RPM to get 400
Hz, or a bit more than 133 revs per second. That's really
humming along.
When I was younger, and found a tank gyro about 3 in diameter,
it needed
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