Electric Kart using arduino uno ?

Projects General Guidance
1

Hello everyone,

I'm new in the world of arduino, electronics and mechanics, and I have a school project in which i have to control an electric kart with bluetooth and with a real joystick ( so 2 modes of control ). I have a few question about the feasibility of my project that i'm going to ask you :

About the motors :

I have two 350 W DC motors taken from a segway and the batteries that goes with each one. To control them, i'll obviously need a motor shield and i found one from polulu : VNH5019 2*12A
( http://www.gotronic.fr/art-shield-moteur-vnh5019-2-x-12-a-21710.htm)
It says that it can control 2 DC motors one way or another and separately, but i'm not sure about the amperage and I don't really know much about this, so do you think this shield will be okay to use for my project ?

About the shields :
If i understood it well, I will have to add two shields to my arduino uno, one for the bluetooth ( i already have the seeedstudio v2.0 bluetooth shield wich i'm working on) and one for the motors, is that right ?
Will my arduino uno be able to bear those two shields ( i think so but i'm not totally sure ) and if so, how does it works for the power supply ?

About the arduino :

Is a arduino uno "strong" enough to lead such a project, or should i move to arduino mega, knowing that the only thing that could be added to the 2 motors and the joysticks would be some LEDS ?

I hope i'm on right section for this post, tell me if not and i'll rewrite my post in the right section.
Also, don't hesitate to tell me if some parts of my post are unclear, i'm french and new to the electronics world so i may not be always using the rights words to express myself.

Anyway thanks in advance for your time and have a great day :slight_smile:

2

but i'm not sure about the amperage

I don't know what voltage the Segway operates on, but let's say 12 volts.
350W / 12 V is as close to 30 amps as makes very little difference.

3

I don't really know how i can find the voltage for the segway since it's not written anywhere, but on the batteries it's written :
Battery : Li-Ion NMC CApacity 36V 4.4Ah

So if i'm not sure about this calculation but does that mean that the motors works on 350/36 ~ 10 A ?
If so, this shield will be adequate right ?

4

Hi,

Before we go any further, what is your electronics, programming, arduino, hardware experience?

Thanks.. Tom.. :slight_smile:

5

Darzang:
I don't really know how i can find the voltage for the segway since it's not written anywhere, but on the batteries it's written :
Battery : Li-Ion NMC CApacity 36V 4.4Ah

So if i'm not sure about this calculation but does that mean that the motors works on 350/36 ~ 10 A ?
If so, this shield will be adequate right ?

A little reading tells me that the Segway runs on 72V. (Two 36V in series.) Some use a pair of 36V Ni-MH batts and some use Li-Ion batteries.

So the current is no problem at 350W/72V, but the motor shield you linked appears to only be able to handle 24V.

There's some more basic info on the Segway here:- Segway

6

For TomGeorge :

I'm learning about electronics since only a month or so, so i don't know much at the moment but i'm learning everyday
I'm using the C and C++ langages for over a year now so i'm kinda used to it, and i don't think it's this part that will cause me troubles.
That's my first project on arduino, but I understand the basics of input/outputs etc so i understand how this thing works, roughly, i'm just terrible about the power supplies :slight_smile:
What do you mean by hardware experience ? Like if i have already done project like that ? If so the answer is no, sadly :confused:

For OldSteve :

The batteries are 2*36V in series as you said, I don't know if it changes anything but my segway is not the type with a handle but like this one :

Also, i don't understand your calculation, if i have 2*350 W motors, shouldn't it be 700W/72V ?
In any ways, with 350/72 or 700/72, i still find an amperage below 10 A, and my shield is supposed to be able to control 2 motors to max 12 A ( that's how i understood it, i may be wrong here), so i don't really understand what you mean by " but the motor shield you linked appears to only be able to handle 24V. "

Thanks for you answers and your time :slight_smile:

7

Darzang:
For OldSteve :

The batteries are 2*36V in series as you said, I don't know if it changes anything but my segway is not the type with a handle but like this one :

Right. They're usually known as a "Hoverboard" here, not just as a "Segway".

Also, i don't understand your calculation, if i have 2*350 W motors, shouldn't it be 700W/72V ?

Total power dissipation would be 700W, but from the point of view of the controller it's two channels of 350W. (One per motor) they're driven separately. The motor shield has 2 x 12A channels rated at 5.5V to 24V.

In any ways, with 350/72 or 700/72, i still find an amperage below 10 A, and my shield is supposed to be able to control 2 motors to max 12 A ( that's how i understood it, i may be wrong here), so i don't really understand what you mean by " but the motor shield you linked appears to only be able to handle 24V. "

Look closely at the ratings for the shield that you linked. The maximum voltage that it can switch is 24V, as I said. If you connect 72V to it, you will destroy it!
Pololu Dual VNH5019 Motor Driver Shield for Arduino
Shield moteur VNH5019 2 x 12 A

8

I don't understand the part with " rated at 5.5V to 24V ", in my mind the batteries are used to power the motors and the shield is powered by a 9V battery, i don't understand why it would destroy it if they're not connected to each other ? I think i have a huge misunderstanding here :slight_smile:

I looked on the website of polulu for some other shields, and i found this one, which " supports a wide 6.5 V to 40 V voltage range and is efficient enough to deliver a continuous 21 A without a heat sink "
Would the voltage range be enough for one motor, or i need a shield that supports ~70V ?

9

Darzang:
I don't understand the part with " rated at 5.5V to 24V ", in my mind the batteries are used to power the motors and the shield is powered by a 9V battery, i don't understand why it would destroy it if they're not connected to each other ? I think i have a huge misunderstanding here :slight_smile:

You do. I've explained it twice already. I won't repeat myself again. I'm quite obviously wasting my time here.

10

Hi,
If you look at the page you link to you will find in the specs,

VIN

This is the main 6.5 V to 40 V (absolute max) motor power supply connection.

Vin is the supply for your motors, it is connected to the motor control PCB so that motor current will flow from the battery through the motor and controller and back to the battery.

The controller controls the current to control the motor speed, BUT the MOSFETS on the controller PCB can only have up to 40V across them when they are not conducting current, your battery assembly will put more than that across them, 72V, thus they will FAIL, BURN etcetc,.

You need a controller rated at more than 72Vdc and able to control the current you motors are rated at.

Hope this helps.. Tom... :slight_smile:

11

Hi,

Thanks for your explanation, it's getting more clear now :slight_smile:

So i looked for a shield which would support ~70V but i didn't find any, but i found the Pololu High-Power Motor Driver 36v15, which "supports a wide 5.5 to 50 V voltage range and is efficient enough to deliver a continuous 15 A without a heat sink."
link here :

I was wondering if it is possible to power each motor separately, so that i would have one 36V battery for one of this shield and one motor, this way my shields would be supporting enough voltage since it would be only one battery connected to it ?

Again, thank you for your time and have a great day :slight_smile:

12

Darzang:
Hi,

Thanks for your explanation, it's getting more clear now :slight_smile:

So i looked for a shield which would support ~70V but i didn't find any, but i found the Pololu High-Power Motor Driver 36v15, which "supports a wide 5.5 to 50 V voltage range and is efficient enough to deliver a continuous 15 A without a heat sink."
link here :
Pololu High-Power Motor Driver 36v15

I was wondering if it is possible to power each motor separately, so that i would have one 36V battery for one of this shield and one motor, this way my shields would be supporting enough voltage since it would be only one battery connected to it ?

Again, thank you for your time and have a great day :slight_smile:

A shield would power both motors separately, at 72V each. (Assuming they're the same motors as a Segway HT, and the batteries are really connected in series on the Hoverboard as you said.)

So, you pulled apart the Hoverboard for it's batteries and motors. What did it originally use for motor drivers?

N.B. Allowance must be made for freshly charged batteries, too, in which case the voltage of two batteries in series would be about 84V to 88V, not just 72V.
My electric bike's 36V 16Ah lithium-ion battery has an end-of-charge voltage of about 42V to 44V. (I forget exactly now.)

13

Thanks for your answer OldSteve,

On the description of the shield, it's written

" This discrete MOSFET H-bridge motor driver enables bidirectional control of one high-power DC brushed motor. "

So I don't understand why you said "A shield would power both motors separately" since it's only controlling one motor ? I know many shields are able to control 2 motors but i though this one was different, but i'm probably forgetting something here.

For the hoverboard, here's a couple of pictures i've taken during its disassembly :

First one here, where we can see that there is one card for each motor.

Second one with a close up look to the board :

And here's one showing how wires were connected to the board :

I hope those pics will help you and if not, tell me which kind of picture you want and i'll take them.

I'm also going to do some measures today in order to see what are the real values of amperage and voltage, do you think there is some other measures i should do ?

14

Darzang:
Thanks for your answer OldSteve,

On the description of the shield, it's written

" This discrete MOSFET H-bridge motor driver enables bidirectional control of one high-power DC brushed motor. "

So I don't understand why you said "A shield would power both motors separately" since it's only controlling one motor ? I know many shields are able to control 2 motors but i though this one was different, but i'm probably forgetting something here.

I was referring to a typical dual-motor shield, or a pair of drivers. All I meant was that the motors would be powered separately.

For the hoverboard, here's a couple of pictures i've taken during its disassembly :

First one here, where we can see that there is one card for each motor.

This is exactly what I meant.

Now, to what I was about to say:-
Despite the fact that the Segway HT page said they use 72V, and that you said the batteries for your Hoverboard were connected in series, I suspect that the Hoverboard batteres were really connected in parallel, and that the motor voltage is actually 36V.

I just found this, which if true, means you could use a driver rated for >=50V, (to allow for freshly-charged batteries), and 10A continuous.:- Balance Scooters

I typed the above before I saw your photos.
Now that I have seen them, it looks like the article I linked above is correct, and that the motor voltage is 36V. The red and black wires appear to be the power wires from each battery to it's respective motor controller/driver. To be sure, measure the voltage between the red and black wires where they connect to the board.

Edit: Another thing to consider - are the motors DC brush motors, or brushless? -> I just found the answer to that in the article I linked. The motors: DC high-torque brushless servo motors. A normal DC motor driver won't drive them. You'll need two brushless ESCs.
Edit2:Just looking at your photos again. Are the three wires in your bottom photo going from the board to the motor? If so, that' s a very good indication that the motor is indeed a 3-phase brushless DC motor.

15

In short, you need to use all of the electronics in the original machine.

When you think about it, this makes total sense.

16

I'd be interested to know how a Hoverboard is steered. Is it a matter of weight distribution?

@Darzang, if you use one motor on each side of your kart, with your own drivers, how do you plan to balance their speeds so that they share the load evenly?

17

Hello guys,

For OldSteve :

"Edit2:Just looking at your photos again. Are the three wires in your bottom photo going from the board to the motor? If so, that' s a very good indication that the motor is indeed a 3-phase brushless DC motor."

Yes, those wires are connected from the board to the motor
My teacher told me it couldn't be a 3'phases motor since it's working with low tension, also i think i forgot to mention that there is some little wires connected from the board to the motor too, here they are :

My opinion is that the 3 "big" wires are used to control the motor, one for the direction ( forward/backward) one for the speed, and one for the brakes or something like that.
The little wires would be some kind of data coming back from the motor ?
I won't be able to make any measures until next monday, so i will know more about that next week.

About the steering, there is two sensors for each motors, i'll try to show you the best i can with the pictures i've already taken :

The blue arrows shows where are the sensors, so under our feet, the arrow in the middle just indicates that there is no sensors underneath it, but if you press it, it is the same as if you press the top pad.

Here's one picture with all the components, the sensor are going back to their place with a little spring ( I don't know if you can see it on the picture, i'll try to take another one next week if needed)

Here is the other side of the hoverboard :

No pressure:

With pressure :

Hope it will be useful :slight_smile:

For Paul___B :

I understand why you say that I need to use all of the electronics in the original machine, and that does make sense. But i don't want to use all the pieces ( like LEDS, speaker ), i only want to keep the batteries and the motors.

I'm kinda lost with what i must add to my arduino, if i've understand it well there is either a choice with a motor shield, a motor driver ( which like a shield but for only one motor ? i'd need a precision on what is a motor driver and a motor controller compare to a motor shield ), or an electronic speed controler, is that right ?

Again, thank you for your time and have a great day :slight_smile:

18

Hi,
I think everybody had better go back and read your first post, you don't want to rebuild one of these machines, you want to make an electric cart, using the bits from the hoverboard.

Take look here;

It doesn't look like your model, but there must be a teardown for it.

There is so much out there on what is inside your hoverboard and motor, I suggest you google google google.

Tom... :slight_smile:

19

Hi,
Looking at various youtubes, the motor is in the wheel and is a BLDC type , the control board for it is unique.
You can see the PCBs in the wheel that must hold the opto or magnetic interrupters that provide the position feedback for the motor control.

Tom.... :slight_smile:

20

Darzang:
My teacher told me it couldn't be a 3'phases motor since it's working with low tension,

So you are telling us that the teacher knows nothing more about it than you do. It's called "the blind leading the blind"! :astonished:

Darzang:
My opinion is that the 3 "big" wires are used to control the motor, one for the direction ( forward/backward) one for the speed, and one for the brakes or something like that.

Well, your opinion is wrong then. It is in fact a three-phase or "brushless" motor.

Darzang:
The little wires would be some kind of data coming back from the motor ?

That much is correct.

Darzang:
About the steering, there is two sensors for each motors, I'll try to show you the best I can with the pictures I've already taken :

These are not steering, these are the safety interlocks that enable the machine to switch on - only when all four are sensing that your feet are correctly placed. Steering happens somewhat similarly to a Segway - the motor speed depends on how far you tilt that side of the machine. It uses tilt sensors.

Darzang:
I understand why you say that I need to use all of the electronics in the original machine, and that does make sense. But i don't want to use all the pieces ( like LEDS, speaker ), I only want to keep the batteries and the motors.

You do not have any choice. You need the controller board as well as the batteries and the motors. There is no equivalent Arduino "shield". These controllers are called "ESC"s, but will be quite different from those used in model aircraft and drones and as you have determined, require feedback from the sensors inside the motors, so you simply cannot duplicate them any other way.

Darzang:
I'm kinda lost with what i must add to my Arduino, if I've understand it well there is either a choice with a motor shield, a motor driver ( which like a shield but for only one motor ? I'd need a precision on what is a motor driver and a motor controller compare to a motor shield ), or an electronic speed controller, is that right?

You need to reverse-engineer the control boards to determine what the control inputs are and determine how to connect into these with the Arduino. Not easy, but an extremely good exercise in electronic engineering.