Rudimentary PC USB oscilloscope?

Den torsdag den 3. september 2015 kl. 00.30.18 UTC+2 skrev John Doe:

The brush-less motor is a three phase that's why it has three wires

The other wires are probably for hall sensors to detect the motor position for the micro controller that runs the motor driver

there is really nothing much you can do with it

-Lasse

That's how the controller controls the motor? Not with the signal wires?

That's not done inside the motor?

the signal wires tell the controller where the rotor in side the motor is and the controller drives the three "power" wires accordingly

the motor is just coils magnets and sensors to sense position

the stuff inside that potted controller is basically an electronic version of commutator and brushes, with a few more bells and whistles

-Lasse

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.

It would be a lot easier to use an ordinary d.c. brush motor, then control the speed with pulse-width modulation.

150w - 800w scooter motors of that kind are all over eBay & surplus market, pretty cheap.

HTH, James Arthur

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

Here....

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

Think "slot cars" for a mindset.

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

snip

I hobbied in electronics for a while, I'll always miss the power.

Yeah it's easy just talking about building an electric bike. But when you go to actually build it, things get hairy. Unbelievably hairy. You wouldn't believe how difficult actually building stuff can be. For example... In the motor you pointed to in another post, the sprocket is not going to work with a bicycle chain. And Yes, I know you can say but this and but that, but talking about it isn't the same as building it. Let's see your electric bike...

I just ordered a DeWalt DCF899. It's a massive impact wrench. It should make building this thing much less difficult than any other way. And super power. And other things. Time will tell.

--

I'm not going to reply to three different posts, so I put it all here.

Nevermind that. The posts were so close, I mistook them for the same author. But it more or less applies anyway.

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.

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

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!

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.

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.

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.

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

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.

using a drill/impactdriver for driving a bike is fine as a gimmick, but there is no way that it is going to last

-Lasse

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.

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

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