Motorboard project

[Stielz]

Thanks Marc.

I have never seen a flexboard before, your design looks good though. I will be interested to see how your project turns out.

As for your suggestion about the one way clutch bearings, I have considered having something like that. the problem there is that I wont be able to do the braking through the motor (or go in reverse) so I decided to just leave it as it is.

Cheers

[Stielz]

Thanks for the reply and tips. Much appreciated.

Now one final question. Would using an motor like yours be recomended (RC engine) or should I look for motors meant to drive a persons weight like a scooter motor? Mainly hoping that the engine is not overworked due to the weight of the rider.

I would definitely recommend using an RC type motor over a scooter or other motor. These big RC motors are easily capable of driving a persons weight. My motor barely gets warm at all when running on 18.5V and I don't think it will get too hot when running on 37V either unless maybe if I was riding up a long hill. You would only have problems with overheating if you are running the motor at max power for a long period of time.

Also I found that RC motors are more powerful, smaller, lighter, and less expensive than specially built EV motors (unless you can get second hand ones).

You will want one with a low kv value which is why most people use outrunner motors for EV projects. A low kv value means you can do all the gearing in a single chain or belt drive.

[Stielz]

I have just come across this ESC on hobbyking http://www.hobbyking.com/hobbyking/stor ... OPTO_.html

looks very impressive, however it says it is not suitable for mountain boards or other similar EVs. I was wondering if anyone has tried using this ESC with a electric bike or skateboard or other EV?

[Lebowski]

I'm wondering whether this is because it's a sensorless controller. There's a good change the forced startup commutation
(before it switches to true sensorless) cannot be performed correctly when a vehicle is attached to the motor. A prop can
easily be spun on startup.... Maybe this type of controller would be OK if your motor had a clutch somewhere.

What IC where you using in your home-made controller ?

[Stielz]

I think you are right there. Im wondering how fast the motor would have to be going for it to switch to sensorless operation.. like if someone were to give a little push off before giving it some throttle would that be enough to get it straight into sensorless commutation?

Im just wondering because this would be ideal for high power electric skateboards if only it was a sensored ESC.

The IC on the board is a 3 phase gate driver IC (HIP4086), it takes care of stepping up the voltage from the micro controller for the gates of the FETs and also boosting the voltage to above the control battery voltage(12V) for driving the high side N-MOSFETs

[walls99]

Im wondering how fast the motor would have to be going for it to switch to sensorless operation.. like if someone were to give a little push off before giving it some throttle would that be enough to get it straight into sensorless commutation?

This is actually the best way to start a small EV with a brushless motor and a sensorless controller! The minimum speed depends on the Kv of the motor (the lower the better) and the sensitivity of the zero-crossing detection circuit but 10% of the maximum speed should be more than enough. I have actually implemented this starting strategy in my controller http://endless-sphere.com/forums/viewtopic.php?f=35&t=27538 and 1% of the max speed is enough to synchronise the motor (I called it the "Windmill" strategy if you look in the code)

I am just having problems with my home made motor controller when I run it on the 10S lipo pack as it keeps blowing transistors. I have just had my fist go on it today just running it on 5S and it goes well, not overly fast but it has plenty of torque and acceleration.

They are many many ways to blow transistors, so you need to 1st find what is the trigger. Can you observe voltage or current or temperature peak? it is the same transistors on your board? Do you compensate for hall sensor timing delay with the speed of the motor? what transistors are you using?

Obviously the best braking method is regenerative braking as it is the only method that doesnt just convert the kinetic energy into heat in the motor and the controller. However I need a second method of braking for when the battery is fully charged so that I dont have my $250 (NZD) battery pack go up in smoke when the lipo batteries get over charged.

The only way this could be a problem is if you start from the top of a high hill with a freshly fully charged battery pack and continuously brake in regen mode. In real life, regen braking recovers much less energy than what it was required to start moving in the fist place, so you won't overcharge.

[AAAkings]

Thanks. I plan on doing a 2wd one then instead with two seperate motors. I know lower KV is recomended but when comparing the following two engines, which one would be prefered? (Haven't picked batteries or a controller yet)
http://www.hobbyking.com/hobbyking/stor ... Motor.html
http://www.hobbyking.com/hobbyking/stor ... 5240_.html

One final question would be could anyone help recomenend a quality controller for either one of these motors? I read on HumboldtRC's threads that he had issues of them burning up as well as many searches through these forums state that you shouldn't skimp on the controller. (Prefer engine brakeing but it not possible, could try and mount disk brakes instead).

I really hope this doesn't come accross as thread-jacking as there was no intent, I just figured the people reading this forum might have personal experience and recomendations.

Thanks once again!

[addicted2climbing]

Thanks. I plan on doing a 2wd one then instead with two seperate motors. I know lower KV is recomended but when comparing the following two engines, which one would be prefered? (Haven't picked batteries or a controller yet)
http://www.hobbyking.com/hobbyking/stor ... Motor.html
http://www.hobbyking.com/hobbyking/stor ... 5240_.html

One final question would be could anyone help recomenend a quality controller for either one of these motors? I read on HumboldtRC's threads that he had issues of them burning up as well as many searches through these forums state that you shouldn't skimp on the controller. (Prefer engine brakeing but it not possible, could try and mount disk brakes instead).

I really hope this doesn't come accross as thread-jacking as there was no intent, I just figured the people reading this forum might have personal experience and recomendations.

Thanks once again!

Hey AAA Kings,

You might want to start your own thread and ask these questions since this is Stielz Build log... Anyhow, I may be able to answer some of your questions. First off your lucky enough to be starting now after the new SK3 motors have been released and after they actualy have some in stock. I gave up waiting and bought my motors elsewhere and they may not be as good as the SK3 motors are "Supposed" to be; Time will tell on both. The 6364 is a good choice and was the motor I wanted to use, but only had room for a 6354 so thats is what I have. If you have room for the 6374 then you may as well go with that if it is in stock. People have been waiting for the SK3 motors for a while, so you may want to settle on your motor now and get it in order while they have it. All the other items come and go in stock more often and are easier to get. One other bit of HK advice is dont order anything that they dont have in stock otherwise your entire order will be stalled and not ship until they can fill your order complete...

As for controller it will depend on if you want wireless control or not. I am intending to use the HK 150 amp ESC's sice it has a sensor imput and I am adding sensors to my motors. I dont have the electronics skills Stielz has so I am relegated to using off the shelf stuff.

As for batteries, 6S 5000 packs in Parallel seem to be the most widley used if your using an R/C controller. If you use somethign else then you can up the voltage. Maybe we both can convince Stielz to sell us one of his controllers once he has the bugs out...

Anyhow, I have my build log on here as well under "flexboard" and your welcome to look at it as well. Also if you intend to head this route, you may as well start your own as its a great place to ask questions... Do you have your bord yet? If not drop me a PM as I have one I was intending to electrify but have not yet.

Take care,

Marc

[bigmoose]

Show me the bottom of your FET board. I think you have significant layout issues that may be impossible to rectify. Please tell me that the TOP fets are not on one side of the board and the BOTTOM fets (of the H bridge) on the other side!

WIRE (Wicked Infitesimal Resistance Element) or in your case PCB trace material, has impedance, and I believe even moderate dI/dt is creating huge voltage spikes in your layout.

As a rule you want the TOP and BOTTOM FETs of the Hbridge so close together you think they are married.

You also appear to be missing good, low ESR bus capacitance TOP Drain to BOTTOM Source right at the married Hbridge pair of FETs.

[Stielz]

Yes, unfortunately I was unaware of the problems surrounding PCB trace inductance at the time I designed the board. The upper FETs are on one side and the lower FETs are on the other.
I have designed the layout such that it will be easy to put a heat sink on it.

You are quite right, originally I had no low ESR caps and was having huge voltage spikes. I have now added a bunch of small ceramic caps which have made a big improvement, I am now getting voltage spikes of just a few volts.

I have also slowed the switching time to around 2 us n an attempt to reduce di/dt

Since making these changes I have had it running OK on 35V (the limit of the power supply I was using). Still not confident enough in it to try running on my 10s lipo battey pack (42V when fully charged)

Thank you for your help, any advice is much appreciated

PCB bottom

CIMG0136.JPG (138.67 KiB) Viewed 585 times

[amberwolf]

I have also slowed the switching time to around 2 us n an attempt to reduce di/dt

Remember that when using slower switching times, you spend longer in the linear region of the MOSFETs' RDSon curve, and internal heating increases. How significant that is compared to other issues depends on that particular FET's characteristics, and your cooling solutions.

[bigmoose]

You have done all the right things in modification! Congrats! Now if your case will allow it, try to find some inverter rated caps like Luke and I talk about in this thread and lay 4uF across each half bridge Drain to Source. http://endless-sphere.com/forums/viewtopic.php?f=30&t=22194&hilit=low+esr+capacitor

If this was your first controller you did very well! Very well indeed!

[Stielz]

Thanks for the support!

I have some low ESR caps on the way which I will put in place of the big slow caps that I have at the moment.

Another thing I have been wondering is whether most BLDC motor controllers PWM both the upper and lower FETs or do they usually just PWM the lower FET while holding the upper FET on for the entire commutation?

[Stielz]

Still having problems with my motor controller, it runs ok on 21 V but is far too unreliable on 42 V.

I believe much of the problems I am having are due to the layout of my PCB. I am planning to completely redesign a new PCB to hopefully make one that can reliably run on 10S lipo batteries.

Here is how it looks all put together anyway.

First prototype

I should be able to make the second motor controller much smaller than that because I will put the microcontroller directly on the PCB instead of using the development board

[sk8norcal]

very nice!!

would like see a video of it in action..

[uliray]

Awesome work, Any chance of multiple production for sale of the motor mount and axle?

[EBJ]

agreed... Lets see some video footage of this thing when you get a chance.
Looks like fun.

[Stielz]

agreed... Lets see some video footage of this thing when you get a chance.
Looks like fun.

I have been holding off posting a video until I get it running at its full potential.. Its not overly impressive on 18.5V. Plus its out of action at the moment, Im having issues with the motor controller and dont want to sink any more money into buying more transistors that will inevitably blow.

Now that I know a thing or two about motor controllers I am confident that I will be able to make one that works reliably at the full voltage to get some serious power through the motor. I am half way through designing this second Motor controller so hopefully in a week or so I will have that done, then I'll make some videos.

Awesome work, Any chance of multiple production for sale of the motor mount and axle?

Unfortunately I have finished up at uni last week so I no longer have access to the workshops to make more mechanical parts sorry

[uliray]

Well, hope you solve controller issue, and i'm telling you that you'll have a big market for that too if you decide to mass produce.

[addicted2climbing]

Well, hope you solve controller issue, and i'm telling you that you'll have a big market for that too if you decide to mass produce.

Hey Stielz,

Your mtn board looks great. I cant wait to get my flexboard done. I am getting quite close. Anyhow as uliray mentioned above, if you decide to sell your controller board I would be very interested. There are not too many option in the lower voltge range needed for Mtn Boards and I am unsure if the R/C controllers I plan to use will last. I added an optical board to my motors for motor timing and am curious if your board has any imputs for comutation timing?

Take care and please post some videos when you have a chance?

Marc

[Stielz]

Thanks Marc, I will look into the idea of making a few more motor controller boards to sell. However it does need much more development to get it to a stage where it is 100% relaible and rubust.

It does have inputs for commutation timing. I have been using hall sensors but I think optical sensors will work just the same. My ptototype circuit board actually has inputs for 2 sets of motor position sensors. I have been playing around with having one set for neutral timing for low speeds then switching to a second set that are positioned for advanced timing at high speeds.

I am also keen to build a controller that uses sensored timing for start up and then switching to senserless when the motor back EMF is great enough to be used to determine the motor position. The reason I want to try this is because I know it is quite difficult to get the hall or optical sensors positioned perfectly which makes the motor run inefficiently.

I agree with you about the RC car controllers, you deffinitely need a sensored controller for this kind of application. A sensorless one will very quickly blow during start up. There are not many sensored RC controllers available that are powerful enough to run these large outrunner motors.

Anyway, I will make some videos when I get my new controller finished

[Lebowski]

I've been busy with my own controller build and reached some conclusions, things to think about for your
motorboard controller:

- hall sensor or back-emf timing will never give perfect timing
- 2 sets of hall sensors, same thing.

it's generally known here that you need to advance the timing to compensate for the delay
between the voltages from the controller and the actual currents going through the motor
(due to the delay from the motor inductance).
What I think people don't realize is that the amount of necessart advance is dependent on
more things than just motor speed and that you need some heavy duty calculations
to get it correct.... Assuming you know what 'correct' is (opinions vary , FOC in my
opinion is not correct )

[kfong]

I like your motor mount design. I might do something similiar to mine if I get the chance. Currently it's a dedicated ice board.