Forums

A toy oscilloscope for droning?

Started by John Doe January 3, 2019
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.
On Friday, 4 January 2019 03:22:57 UTC, John Doe  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.
There's a wide range of frequency & prices, starting at IIRC under 20 notes for DSO138 that does 1 megasample and about 200kHz. NT
On Fri, 4 Jan 2019 03:22:54 -0000 (UTC), John Doe
<always.look@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. -- Jeff Liebermann jeffl@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 <jeffl@cruzio.com> wrote:

> John Doe > <always.look@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.
On 1/4/2019 12:31 PM, John Doe wrote:
> Jeff Liebermann <jeffl@cruzio.com> wrote: > >> John Doe >> <always.look@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.
On Friday, January 4, 2019 at 3:31:51 PM UTC-5, John Doe wrote:
> Jeff Liebermann <jeffl@cruzio.com> wrote: > > > John Doe > > <always.look@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.
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@cruzio.com> wrote: > > > John Doe > > > <always.look@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
On Fri, 4 Jan 2019 20:31:48 -0000 (UTC), John Doe
<always.look@message.header> wrote:

>Jeff Liebermann <jeffl@cruzio.com> wrote: > >> John Doe >> <always.look@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@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Saturday, 5 January 2019 01:03:38 UTC, Jeff Liebermann  wrote:
> On Fri, 4 Jan 2019 20:31:48 -0000 (UTC), John Doe > <always.look@message.header> wrote: > >Jeff Liebermann <jeffl@cruzio.com> wrote: > >> John Doe > >> <always.look@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
Jeff Liebermann <jeffl@cruzio.com> wrote in 
news:g6vv2e9bm218nv8edh16g9sbidujctg3mc@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.