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A toy oscilloscope for droning?

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John Doe
Guest

Fri Jan 04, 2019 4:45 am   



Less than $100 US. For people who are familiar with current low end
prices. I suppose they're crap to an engineer, but bear with me.

Any recommendation for either a handheld or a PC/USB oscilloscope that
might be fun to use with consumer drones? I see some are for automotive
use, is there something in that? In the measly selection of less than
$100 oscilloscopes, what qualities should I look for? Any specific
recommendation?

Does viewing multiple motors or motor drivers at the same time benefit
anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.


Guest

Fri Jan 04, 2019 2:45 pm   



On Friday, 4 January 2019 03:22:57 UTC, John Doe wrote:
Quote:
Less than $100 US. For people who are familiar with current low end
prices. I suppose they're crap to an engineer, but bear with me.

Any recommendation for either a handheld or a PC/USB oscilloscope that
might be fun to use with consumer drones? I see some are for automotive
use, is there something in that? In the measly selection of less than
$100 oscilloscopes, what qualities should I look for? Any specific
recommendation?

Does viewing multiple motors or motor drivers at the same time benefit
anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.


There's a wide range of frequency & prices, starting at IIRC under 20 notes for DSO138 that does 1 megasample and about 200kHz.


NT

John Doe
Guest

Fri Jan 04, 2019 9:45 pm   



Jeff Liebermann <jeffl_at_cruzio.com> wrote:

Quote:
John Doe
always.look_at_message.header> wrote:

Less than $100 US. For people who are familiar with current low
end prices. I suppose they're crap to an engineer, but bear with
me.

Any recommendation for either a handheld or a PC/USB oscilloscope
that might be fun to use with consumer drones? I see some are for
automotive use, is there something in that? In the measly
selection of less than $100 oscilloscopes, what qualities should I
look for? Any specific recommendation?

Does viewing multiple motors or motor drivers at the same time
benefit anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.

How does zero dollars sound? If you have a computah with a sound
card, try a software based oscilloscope. I use these:
http://www.sillanumsoft.org/prod01.htm
http://www.daqarta.com
Bandwidth depends on the sound card. You'll find 192KHz sampling
rate sound cards all over eBay:
https://www.ebay.com/sch/i.html?_nkw=192khz+sound+card> I suggest
the USB flavor. That will let you see up to about half the
192KHz. However, since your motor drivers produce square waves,
you'll only see half of that again, unless you can live with
looking at sine waves. Find the RPM that your unspecified drone
delivers and calculate the maximum frequency. Since you'll be
looking at something resembling a square wave, you'll need at
least twice that number for your scope bandwidth.


I tried that, long ago. Seems the input impedance was not nearly high
enough to do anything remotely useful.

Jeff Liebermann
Guest

Fri Jan 04, 2019 9:45 pm   



On Fri, 4 Jan 2019 03:22:54 -0000 (UTC), John Doe
<always.look_at_message.header> wrote:

Quote:
Less than $100 US. For people who are familiar with current low end
prices. I suppose they're crap to an engineer, but bear with me.

Any recommendation for either a handheld or a PC/USB oscilloscope that
might be fun to use with consumer drones? I see some are for automotive
use, is there something in that? In the measly selection of less than
$100 oscilloscopes, what qualities should I look for? Any specific
recommendation?

Does viewing multiple motors or motor drivers at the same time benefit
anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.


How does zero dollars sound? If you have a computah with a sound
card, try a software based oscilloscope. I use these:
<http://www.sillanumsoft.org/prod01.htm>
<http://www.daqarta.com>
Bandwidth depends on the sound card. You'll find 192KHz sampling rate
sound cards all over eBay:
<https://www.ebay.com/sch/i.html?_nkw=192khz+sound+card>
I suggest the USB flavor. That will let you see up to about half the
192KHz. However, since your motor drivers produce square waves,
you'll only see half of that again, unless you can live with looking
at sine waves. Find the RPM that your unspecified drone delivers and
calculate the maximum frequency. Since you'll be looking at something
resembling a square wave, you'll need at least twice that number for
your scope bandwidth.

--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

George Herold
Guest

Fri Jan 04, 2019 10:45 pm   



On Friday, January 4, 2019 at 3:31:51 PM UTC-5, John Doe wrote:
Quote:
Jeff Liebermann <jeffl_at_cruzio.com> wrote:

John Doe
always.look_at_message.header> wrote:

Less than $100 US. For people who are familiar with current low
end prices. I suppose they're crap to an engineer, but bear with
me.

Any recommendation for either a handheld or a PC/USB oscilloscope
that might be fun to use with consumer drones? I see some are for
automotive use, is there something in that? In the measly
selection of less than $100 oscilloscopes, what qualities should I
look for? Any specific recommendation?

Does viewing multiple motors or motor drivers at the same time
benefit anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.

How does zero dollars sound? If you have a computah with a sound
card, try a software based oscilloscope. I use these:
http://www.sillanumsoft.org/prod01.htm
http://www.daqarta.com
Bandwidth depends on the sound card. You'll find 192KHz sampling
rate sound cards all over eBay:
https://www.ebay.com/sch/i.html?_nkw=192khz+sound+card> I suggest
the USB flavor. That will let you see up to about half the
192KHz. However, since your motor drivers produce square waves,
you'll only see half of that again, unless you can live with
looking at sine waves. Find the RPM that your unspecified drone
delivers and calculate the maximum frequency. Since you'll be
looking at something resembling a square wave, you'll need at
least twice that number for your scope bandwidth.

I tried that, long ago. Seems the input impedance was not nearly high
enough to do anything remotely useful.


The low end Rigol is now only $260
https://www.rigolna.com/products/digital-oscilloscopes/1000/

George H.

Mike
Guest

Fri Jan 04, 2019 10:45 pm   



On 1/4/2019 12:31 PM, John Doe wrote:
Quote:
Jeff Liebermann <jeffl_at_cruzio.com> wrote:

John Doe
always.look_at_message.header> wrote:

Less than $100 US. For people who are familiar with current low
end prices. I suppose they're crap to an engineer, but bear with
me.

Any recommendation for either a handheld or a PC/USB oscilloscope
that might be fun to use with consumer drones? I see some are for
automotive use, is there something in that? In the measly
selection of less than $100 oscilloscopes, what qualities should I
look for? Any specific recommendation?

Does viewing multiple motors or motor drivers at the same time
benefit anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.

How does zero dollars sound? If you have a computah with a sound
card, try a software based oscilloscope. I use these:
http://www.sillanumsoft.org/prod01.htm
http://www.daqarta.com
Bandwidth depends on the sound card. You'll find 192KHz sampling
rate sound cards all over eBay:
https://www.ebay.com/sch/i.html?_nkw=192khz+sound+card> I suggest
the USB flavor. That will let you see up to about half the
192KHz. However, since your motor drivers produce square waves,
you'll only see half of that again, unless you can live with
looking at sine waves. Find the RPM that your unspecified drone
delivers and calculate the maximum frequency. Since you'll be
looking at something resembling a square wave, you'll need at
least twice that number for your scope bandwidth.

I tried that, long ago. Seems the input impedance was not nearly high
enough to do anything remotely useful.


That sounds off...
Sure, you can come up with many situations that require very high impedance.
But there's lotsa stuff that will work just fine.
The big problem is making sure you have enough series resistance
and clamp diodes so you don't blow up your sound card when you probe
the wrong place.


Guest

Fri Jan 04, 2019 11:45 pm   



On Friday, 4 January 2019 21:38:31 UTC, George Herold wrote:
Quote:
On Friday, January 4, 2019 at 3:31:51 PM UTC-5, John Doe wrote:
Jeff Liebermann <jeffl_at_cruzio.com> wrote:
John Doe
always.look_at_message.header> wrote:

How does zero dollars sound? If you have a computah with a sound
card, try a software based oscilloscope. I use these:
http://www.sillanumsoft.org/prod01.htm
http://www.daqarta.com
Bandwidth depends on the sound card. You'll find 192KHz sampling
rate sound cards all over eBay:
https://www.ebay.com/sch/i.html?_nkw=192khz+sound+card> I suggest
the USB flavor. That will let you see up to about half the
192KHz. However, since your motor drivers produce square waves,
you'll only see half of that again, unless you can live with
looking at sine waves. Find the RPM that your unspecified drone
delivers and calculate the maximum frequency. Since you'll be
looking at something resembling a square wave, you'll need at
least twice that number for your scope bandwidth.

I tried that, long ago. Seems the input impedance was not nearly high
enough to do anything remotely useful.

The low end Rigol is now only $260
https://www.rigolna.com/products/digital-oscilloscopes/1000/

George H.


50MHz 2 channel for $259 is poor compared to something used on ebay. You can get analogue storage too for less than that. Telequipments are relatively good deals for folks that don't need Tek specs.

192kHz sampling might let you see that 96kHz is present, but to see the waveform you need way more samples, bringing f_max down to around 20kHz at best.


NT

Jeff Liebermann
Guest

Sat Jan 05, 2019 2:45 am   



On Fri, 4 Jan 2019 20:31:48 -0000 (UTC), John Doe
<always.look_at_message.header> wrote:

Quote:
Jeff Liebermann <jeffl_at_cruzio.com> wrote:

John Doe
always.look_at_message.header> wrote:

Less than $100 US. For people who are familiar with current low
end prices. I suppose they're crap to an engineer, but bear with
me.

Any recommendation for either a handheld or a PC/USB oscilloscope
that might be fun to use with consumer drones? I see some are for
automotive use, is there something in that? In the measly
selection of less than $100 oscilloscopes, what qualities should I
look for? Any specific recommendation?

Does viewing multiple motors or motor drivers at the same time
benefit anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.

How does zero dollars sound? If you have a computah with a sound
card, try a software based oscilloscope. I use these:
http://www.sillanumsoft.org/prod01.htm
http://www.daqarta.com
Bandwidth depends on the sound card. You'll find 192KHz sampling
rate sound cards all over eBay:
https://www.ebay.com/sch/i.html?_nkw=192khz+sound+card> I suggest
the USB flavor. That will let you see up to about half the
192KHz. However, since your motor drivers produce square waves,
you'll only see half of that again, unless you can live with
looking at sine waves. Find the RPM that your unspecified drone
delivers and calculate the maximum frequency. Since you'll be
looking at something resembling a square wave, you'll need at
least twice that number for your scope bandwidth.

I tried that, long ago. Seems the input impedance was not nearly high
enough to do anything remotely useful.


No numbers (again). No model number (again). No clue as to the maker
and model number of the brushless motors so I can calculate the
required scope bandwidth. Numbers are a good thing to have.

What input impedance to your scope would you like to see? For your
stepper motor, you're looking at some very low H bridge output
impedances. Typical will be 5V and 1A drive. That's 5 ohms output
impedance. Just about any scope input impedance from 50 ohms and up
will read correctly without loading a 5 ohms source.

Last time I played with a cheap USB sound dongle, the input impedance
was about 10K ohms. Not great, but useful. Want more? Just add some
series resistance and maybe a real X10 scope probe.

Sound Card Input Impedance
<http://www.daqarta.com/dw_0azz.htm>

A more serious problem is that the sound card input only tolerates a
+/- 2.5V swing. You can overdrive it a little without blowing
something up, but unless you install an input attenuator and/or
limiter to keep the input swing within reasonable limits, you're going
to blow up the card.

"Sound Card Input Range and Limiter Circuits"
<http://www.daqarta.com/dw_0all.htm>

However, reading between your lines, I suspect that you want a ready
to run solution and not an engineering project consisting of adding
about 6 resistors, 4 diodes, and 2 scope probes. Therefore I suggest
you buy a used Tektronix scope on eBay. There are a few available for
under $100, but with shipping costs at around $50, methinks you'll
need to raise your target price. Also, I can't offer a specific
suggestion without knowing your performance requirements.

Good luck.



--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


Guest

Sat Jan 05, 2019 2:45 am   



On Saturday, 5 January 2019 01:03:38 UTC, Jeff Liebermann wrote:
Quote:
On Fri, 4 Jan 2019 20:31:48 -0000 (UTC), John Doe
always.look_at_message.header> wrote:
Jeff Liebermann <jeffl_at_cruzio.com> wrote:
John Doe
always.look_at_message.header> wrote:

Less than $100 US. For people who are familiar with current low
end prices. I suppose they're crap to an engineer, but bear with
me.

Any recommendation for either a handheld or a PC/USB oscilloscope
that might be fun to use with consumer drones? I see some are for
automotive use, is there something in that? In the measly
selection of less than $100 oscilloscopes, what qualities should I
look for? Any specific recommendation?

Does viewing multiple motors or motor drivers at the same time
benefit anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.

How does zero dollars sound? If you have a computah with a sound
card, try a software based oscilloscope. I use these:
http://www.sillanumsoft.org/prod01.htm
http://www.daqarta.com
Bandwidth depends on the sound card. You'll find 192KHz sampling
rate sound cards all over eBay:
https://www.ebay.com/sch/i.html?_nkw=192khz+sound+card> I suggest
the USB flavor. That will let you see up to about half the
192KHz. However, since your motor drivers produce square waves,
you'll only see half of that again, unless you can live with
looking at sine waves. Find the RPM that your unspecified drone
delivers and calculate the maximum frequency. Since you'll be
looking at something resembling a square wave, you'll need at
least twice that number for your scope bandwidth.

I tried that, long ago. Seems the input impedance was not nearly high
enough to do anything remotely useful.

No numbers (again). No model number (again). No clue as to the maker
and model number of the brushless motors so I can calculate the
required scope bandwidth. Numbers are a good thing to have.

What input impedance to your scope would you like to see? For your
stepper motor, you're looking at some very low H bridge output
impedances. Typical will be 5V and 1A drive. That's 5 ohms output
impedance. Just about any scope input impedance from 50 ohms and up
will read correctly without loading a 5 ohms source.

Last time I played with a cheap USB sound dongle, the input impedance
was about 10K ohms. Not great, but useful. Want more? Just add some
series resistance and maybe a real X10 scope probe.

Sound Card Input Impedance
http://www.daqarta.com/dw_0azz.htm

A more serious problem is that the sound card input only tolerates a
+/- 2.5V swing. You can overdrive it a little without blowing
something up, but unless you install an input attenuator and/or
limiter to keep the input swing within reasonable limits, you're going
to blow up the card.

"Sound Card Input Range and Limiter Circuits"
http://www.daqarta.com/dw_0all.htm

However, reading between your lines, I suspect that you want a ready
to run solution and not an engineering project consisting of adding
about 6 resistors, 4 diodes, and 2 scope probes. Therefore I suggest
you buy a used Tektronix scope on eBay. There are a few available for
under $100, but with shipping costs at around $50, methinks you'll
need to raise your target price. Also, I can't offer a specific
suggestion without knowing your performance requirements.

Good luck.


A x10 probe on a 10k input will act as a lot more than x10. It will probably be unusable.

I've fixed TVs with a lot worse than a crappy scope when younger. Almost every tool has some use.


NT

DLUNU
Guest

Sat Jan 05, 2019 2:45 am   



Jeff Liebermann <jeffl_at_cruzio.com> wrote in
news:g6vv2e9bm218nv8edh16g9sbidujctg3mc_at_4ax.com:

Quote:
but unless you install an input attenuator and/or
limiter to keep the input swing within reasonable limits, you're going
to blow up the card.


Well... not neccessarily blow it up, but at the very least all the
input data will be clipped flat. At some point the voltage will be
enough to blow the input amp sections of the sound card.

Jeff Liebermann
Guest

Sat Jan 05, 2019 8:45 pm   



On Fri, 4 Jan 2019 17:08:15 -0800 (PST), tabbypurr_at_gmail.com wrote:

Quote:
A x10 probe on a 10k input will act as a lot more than x10.
It will probably be unusable.


Oops. The x10 passive probe uses a 9M input resistor and assumes a 1M
input impedance to the scope. With a 10K scope (sound card) input
impedance, that would be about a 900:1 probe. Yep, useless.

However, I could swear that I was using a x10 probe and getting decent
looking audio signals, but maybe not. Next time I visit my palatial
office, I'll check.

Yet another input protection circuit:
<http://homediyelectronics.com/projects/howtomakeafreesoundcardpcoscilloscope/?p=3>
<http://homediyelectronics.com/projects/howtomakeafreesoundcardpcoscilloscope/>

Quote:
I've fixed TVs with a lot worse than a crappy scope when younger.
Almost every tool has some use.


Same here. My signal source was 60Hz hummm from touching an input
with my finger. There was also the "signal tracer" for determining
where the signal disappeared.
<https://people.ohio.edu/postr/bapix/SigTrac1.htm>
<https://people.ohio.edu/postr/bapix/SigTrac2.htm>
However, I don't think those would be very useful with todays
electronics or for fixing drones.


--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann
Guest

Sat Jan 05, 2019 8:45 pm   



On Sat, 5 Jan 2019 01:14:10 +0000 (UTC), DLUNU
<DecadentLinuxUserNumeroUno_at_DLU.org> wrote:

Quote:
Jeff Liebermann <jeffl_at_cruzio.com> wrote in
news:g6vv2e9bm218nv8edh16g9sbidujctg3mc_at_4ax.com:

but unless you install an input attenuator and/or
limiter to keep the input swing within reasonable limits, you're going
to blow up the card.

Well... not neccessarily blow it up, but at the very least all the
input data will be clipped flat. At some point the voltage will be
enough to blow the input amp sections of the sound card.


I blew up the left channel input on 3 of this type of sound card
dongle before I realized what was happening:
<https://www.ebay.com/itm/142191444372>
I think I was feeding it a -10V to +10V square wave. I don't know if
it was over voltage, running the input below ground, or both that blew
up the input.

Note: I use such cheap external USB sound card dongles because I
really don't like replacing the sound chips on my laptop motherboard.


--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jasen Betts
Guest

Sat Jan 05, 2019 9:45 pm   



On 2019-01-05, Jeff Liebermann <jeffl_at_cruzio.com> wrote:
Quote:
On Fri, 4 Jan 2019 17:08:15 -0800 (PST), tabbypurr_at_gmail.com wrote:

A x10 probe on a 10k input will act as a lot more than x10.
It will probably be unusable.

Oops. The x10 passive probe uses a 9M input resistor and assumes a 1M
input impedance to the scope. With a 10K scope (sound card) input
impedance, that would be about a 900:1 probe. Yep, useless.

However, I could swear that I was using a x10 probe and getting decent
looking audio signals, but maybe not. Next time I visit my palatial
office, I'll check.


the 16-bit DAC will compensate somewhat for the lost amplitude, and a
~50:1 "mic boost" option could help too.

--
When I tried casting out nines I made a hash of it.

John Larkin
Guest

Sat Jan 05, 2019 9:45 pm   



On Fri, 4 Jan 2019 14:38:49 -0800 (PST), tabbypurr_at_gmail.com wrote:

Quote:
On Friday, 4 January 2019 21:38:31 UTC, George Herold wrote:
On Friday, January 4, 2019 at 3:31:51 PM UTC-5, John Doe wrote:
Jeff Liebermann <jeffl_at_cruzio.com> wrote:
John Doe
always.look_at_message.header> wrote:

How does zero dollars sound? If you have a computah with a sound
card, try a software based oscilloscope. I use these:
http://www.sillanumsoft.org/prod01.htm
http://www.daqarta.com
Bandwidth depends on the sound card. You'll find 192KHz sampling
rate sound cards all over eBay:
https://www.ebay.com/sch/i.html?_nkw=192khz+sound+card> I suggest
the USB flavor. That will let you see up to about half the
192KHz. However, since your motor drivers produce square waves,
you'll only see half of that again, unless you can live with
looking at sine waves. Find the RPM that your unspecified drone
delivers and calculate the maximum frequency. Since you'll be
looking at something resembling a square wave, you'll need at
least twice that number for your scope bandwidth.

I tried that, long ago. Seems the input impedance was not nearly high
enough to do anything remotely useful.

The low end Rigol is now only $260
https://www.rigolna.com/products/digital-oscilloscopes/1000/

George H.

50MHz 2 channel for $259 is poor compared to something used on ebay. You can get analogue storage too for less than that. Telequipments are relatively good deals for folks that don't need Tek specs.

192kHz sampling might let you see that 96kHz is present, but to see the waveform you need way more samples, bringing f_max down to around 20kHz at best.


NT


The Rigols are small, light, cool, reliable, and have color displays,
and usually come with probes. You get perfect storage, signal
averaging, RMS, FFTs, measurement cursors, trigger tricks, and it's a
pretty good frequency counter.

I had a Telequipment once. Hated it.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

speff
Guest

Sat Jan 05, 2019 10:45 pm   



On Thursday, 3 January 2019 22:22:57 UTC-5, John Doe wrote:
Quote:
Less than $100 US. For people who are familiar with current low end
prices. I suppose they're crap to an engineer, but bear with me.

Any recommendation for either a handheld or a PC/USB oscilloscope that
might be fun to use with consumer drones? I see some are for automotive
use, is there something in that? In the measly selection of less than
$100 oscilloscopes, what qualities should I look for? Any specific
recommendation?

Does viewing multiple motors or motor drivers at the same time benefit
anything? Or is a single channel enough?

Of course I want it to be useful, but it's as much for amusement.


Those little LCD ARM based things are basically junk and are expensive for what functionality they offer.

Save your pennies for a Rigol or Owon. You will not regret it.

--Spehro Pefhany

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