Rudimentary PC USB oscilloscope?

My main question is about PC USB-based oscilloscopes. The rest of this is specific to my problem(s) and may be overlooked.

I'm using cordless drills to power electric bicycles. I have one built. It works but is underpowered. I am building a better one using a DeWalt DCD995. Some nice electronics included in that drill, a stout (very tight turning) brushless motor with a controller.

It has a few inputs from the speed switch and clutch.

It has 5 data/signal outputs from the controller to the motor. One wire is purple, the other four wires are black.

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It also has three heavy-duty wires going to the motor. I've been told that the drill uses AC, so maybe that's what the extra power wire is for, I dunno.

I desperately need to disable some of the motor's functions, so I need to know what the various wires do. Since it's probably a DeWalt specific motor, looking for data would be a waste of time?

The three heavy-duty wires... Do you guess they control any of the functions or are they simply for supplying power?

Thanks.

Reply to
John Doe
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Not sure can be of much help but that motor and pinion is $54 from Dewalt. They have exploded view but little else. Would have to unpot the controller and go from there I guess. Unless you can come up with some numbers to search for.

Reply to
Ron M.

Thanks to the replies.

FWIW... My interest in this might be waning even though I already bought one DCD995 impact driver and dissected it, besides making one electric bike already. Now I'm thinking an impact wrench instead. Apparently impact wrenches are meant for torque in the reverse direction. That should mean they can be efficiently placed on the left side of the bicycle bottom bracket, opposite the sprocket. And of course disabling the impact function. DeWalt sells variable speed models geared even lower than my DCD995.

Reply to
John Doe

On Wed, 2 Sep 2015 22:28:23 +0000 (UTC), John Doe Gave us:

Here....

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Look at the rest of the page too. There are even controllers.

Think "slot cars" for a mindset.

Reply to
DecadentLinuxUserNumeroUno

On Thu, 03 Sep 2015 02:07:27 -0400, DecadentLinuxUserNumeroUno Gave us:

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Reply to
DecadentLinuxUserNumeroUno

If you have built an electric bike, I'd like to see it. I have been doing this for a long time and I'm familiar with most methods. Hub motors are still pretty expensive.

If it were cheap or easy to build a robust electric bike, the fast ones wouldn't be selling for $10,000 US.

I just ordered a DeWalt DCF899 for $209 (total). It's a massive impact wrench that goes with the batteries and charger I have. It should make building this thing much less difficult than any other way. And super power. Good efficiency. Ultra durable. And other things. Time will tell. If and when completed, I'll probably post it on my YouTube page (pqxxedf).

This is way off topic, at least for this thread, so I'll see you later.

Reply to
John Doe

You can use any sound card, including USB sound devices, as a scope input. HOWEVER, note that all sound cards are AC coupled (even the ones that claim otherwise, it appears), though that may not be an issue for you if the motor really uses AC.

Also note that sound card inputs are typically good for only

1-2 V before clipping, so you'll need an input limiter and/or voltage divider. A simple circuit to do both is at .

Best regards,

Bob Masta DAQARTA v8.00 Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, Pitch Track, Pitch-to-MIDI FREE 8-channel Signal Generator, DaqMusiq generator Science with your sound card!

Reply to
Bob Masta

On Thu, 3 Sep 2015 08:20:50 +0000 (UTC), John Doe Gave us:

And would build you a ten mph bike.

The hub motors you so swiftly dismissed were only a hundred dollars more, and take your bike to 30 mph, and they have front wheel versions too.

Reply to
DecadentLinuxUserNumeroUno

On Thu, 3 Sep 2015 08:20:50 +0000 (UTC), John Doe Gave us:

The hub motor is a bolt on accessory.. It comes with the wheel, ya dope. They had the wheel, tire battery pack, and controller and some even had a disc brake with them. Sheesh.

Reply to
DecadentLinuxUserNumeroUno

Yeah, I did that once. As I recall, it didn't work very well because (for one reason) the input impedance wasn't very high.

Reply to
John Doe

Two of the wires are GND and supply for the hall sensors. The remaining three are signals from the hall sensor inside the motor to the speed controller.

The motor is a three phase motor, so it needs three wires. The controller switches the battery voltage so that the motor will get the proper AC power. The hall sensors allow the controller to figure out which phases it must send current through to get the motor to go in the correct direction with maximum torque.

Mechanically, the motor is probably application specific, but otherwise, it looks like it is a perfectly normal brushless motor with position sensors. The remote control hobbyists call it a sensored motor, as opposed to a sensorless motor.

The two motor types are used for different applications. A sensorless motor has very poor starting torque, while a sensored motor has full torque at zero speed. If the motor is driving a propeller or a helicopter rotor, starting torque is not important, so sensorless motors are used. For cars or servos, on the other hand, sensored motors are used, since acceleration is important in those applications.

The motor itself has no other functions than to turn one way or the other. Any other functionality is provided by the controller. If you want it to behave differently, you would have to modify or replace the controller. I would not be surprised if this motor would work perfectly if hooked up to a standard RC controller.

--
RoRo
Reply to
Robert Roland

Strangely enough, impact wrenches don't work the way most tools do. In the case of the multiple speed Dewalt DCF899 monster impact wrench, low "gear" isn't actually a gear and actually provides less power than high "gear". Because speed is controlled by the controller and not by gearing.

I find out that after ordering one. Arg.

Reply to
John Doe

That's very interesting. I just ordered a monster impact wrench (DeWalt DCF899). Then found out low gear wasn't a gear, but instead the speed was a controller function. Torque is actually less at low maximum RPM. But seems they won't cancel the order.

But hopefully it's the sensored motor you describe.

Torque is really all that matters (yeah, right). If the thing is set on high RPM where it has maximum torque, as long as it has full torque (that is, the greater torque per the higher RPM setting) regardless of the RPM, I can apply throttle until it gets me to the desired speed. As long as bogging down at low RPM per maximum RPM isn't hurting the motor. I would think that a fancy controller would prevent overcurrent. And as long as the acceleration isn't too much. Maybe a spring coupling would be useful. Or I can put it on a scooter with very small wheels, har har har.

Reply to
John Doe

On Thu, 3 Sep 2015 16:18:42 +0000 (UTC), John Doe Gave us:

There are some pretty nice actual "USB oscilloscopes" out there.

Reply to
DecadentLinuxUserNumeroUno

You usually get a better, and cheaper, scope by buying a real oscilloscope. The Rigols are fine.

Reply to
John Larkin

On Thu, 03 Sep 2015 14:19:09 -0700, John Larkin Gave us:

No shit. I was simply telling him about his USB endeavors.

I bought 3 Tektronix scopes in the last week, and even a nice analog unit last month. As well as two network analyzers, and two signal generators.

Bought a cheap chinese sig gen last month. It is nowhere near as useful as the HP. The USB scope is pretty much a cursory baseline thing which barely does what it claims to do.

It is a Virtin's Technology Multi-instrument.

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Reply to
DecadentLinuxUserNumeroUno

The claim that standalone units are cheaper for the same functionality sounds like BS to me. I did scope them out yesterday... Lots of comments on the PC USB scopes by people who have actually bought them suggest otherwise.

But I'm not interested in entertaining trolls on this contentious issue. Have fun.

Reply to
John Doe

I picked up a low end Hantek MSO a few months ago. I don't know how well it can work because I never got the software to install properly. The seller gave me my money back because the shipper lost all tracking info. Easier than arguing over the perceived value of a device I can't get to work.

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Rick
Reply to
rickman

I would expect a USB scope to be cheaper if nothing else, because there is no display and control hardware. But it doesn't seem to pan out that way.

I want a USB scope so I can put it in my computer bag and capture screens on the laptop. I want to have it all portable in one bag with the PC.

But then it looks like I may need a new PC. The only thing I can access on the Internet is newsgroup access. I wonder if any laptops come with a built in oscope yet?

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Rick
Reply to
rickman

I'd rather have the low-end 100 MHz Rigol. The Rigol samples at 1 GHz, but the Virtin samples at 100 MHz in 2-channel mode. The Rigol is cheaper, although it doesn't include the ARB.

It clearly can't be a dual-channel 80 MHz scope, sampling at 100 MHz. It's marginal in single-channel mode.

Connecting a laptop, and installing all that software and stuff, sounds like a nuisance to me, too.

The Virtin sort of thing might be useful in automated test sets.

Reply to
John Larkin

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