Easy build self balancing electric skateboard

Step 47 Full code (potentiometer steering)

This version of the code is almost the same as previous one except we are now using a 10K potentiometer to steer and another to fine-tune the balance point insted of the rocker switches described in this instructable.
It is attached as a text file to copy and paste into a new arduino sketch, compile and save.

Open this sketch. We need to adjust the value of 338 to fine tune the balance point as before:
How to do this:
As when we tweaked the IMU tester: alter the value of 338 (if you need to) in this line of code in for the value you wrote down for accsum when running IMU tester and holding your board level: x_accdeg = (float)((accsum - 338) * 0.862);

Recompile the balance code with this new value in and you are now ready to try it out.
NOTE:
Updated February 25th 2012.
It works with Arduino V22. They have now released a newer version (V1.0) with a new softserial library with slightly different softserial commands so it might not work with very latest version of Arduino.





If you open up a proper Nintenso Wii Nunchuck (with special 3 lobed "Nintendo" screwdriver you have to buy on ebay) you will see that under thumb joystick is catually just 2 x 16 k potentiometers, one for side to side movement (steering) and another for forward/back (fine tune balance point). If you have a Chinese copy the potentiometer is about 3.5K, you can tell difference by the price as they look identical. You can actually solder wires onto the 3 pins of each potentiometer if you are careful and also 2 wires to one of the end buttons to use as a the deadman switch. Good thing about these potentiometers is that they self-centre at about 5-7 K Ohms.

Use multicore cable and run it back to your arduino board and you have a neat hand controller.
You may possibly have to alter values slightly in the code for the readings on analog ports on a scale from 0 - 1023

Comments

[aniles jr]

In this code dose it have to highest the motors can go is 50%?


dreniles

thank you

[XenonJohn]

The code can be altered so the motor speed is limited to 50 percent. Buzzer can be added to give warning when power reaches any value you want to set.

I have done all these things with my own projects. However, purpose of this instructable was to keep thiings fairly simple, more complexity means more things to go wrong.

You have to get it balancing first, then you add in clever features afterwards.

John

[aniles jr]

thank you how long do you thing it will take me to get it to balence

[XenonJohn]

Took me 3 sleepless months first time around. I have saved you so much hassle.
If you follow instructable sometimes people get the IMU back to front and things like that. Should be pretty quick so long as no faulty components or dry solder joints, misaligned drive chains and so on.

The IMU tester and motor tester software examples are there to help spot some of these basic problems before you get to the first self-balance test.

[aniles jr]

i appercatie all your help john i cant thank you enough i did the motor test and the IMU test and it worked perfect. but when i let go of the kill bottom it stops hard when it post to go to the next % this is how it went 10.00 20.00 30.00 40.00 50.00 40.00( let go of the kill switch) and then finish with the 40.00 then is stops hard when you let go of the kill switch is it post to stop keep balancing?




Thank you very much

[XenonJohn]

In the motor tester sketch motor power goes up to 50% in 10% steps, it seemed safer that way.

In main code for balancing machine, it can go up to 100%.

[aniles jr]

For the main code can i limit it to 50%. and when im useing the POT to steer do i turn the POT to the middle and then turn left to right?

[aniles jr]

and how do i wire the pot's

[tracer11lb]

Hi,

I know its been awhile since the last comment but I was just wondering if I can use a motor with built in motor controller? thanks

[XenonJohn]

Hi,

Motor with a built in controller could be used if arduino can talk to the controller OK.
Remember it has to be able to go from forward to reverse with no delays or problems. Also need high torque ideally.
However the motor web page you gave me the link to shows brushless servo motors with integrated encoders (position encoders). These tell an external brushless motor controller how to turn the motor.
I could not see one there with a built in motor controller.

I have stuck to brushed motors with robot H-bridge controllers for now as brushless controllers seem more complex to get control of with an Arduino board.

If anyone knows how to reliably control an affordable hubless motor controller with an Arduino I would like to know as then I will get a 1000Watt Chinese e-bike wheel with brushless pancake hub motor and build a self-balancing unicycle!

John

[bschulth]

Has anyone updated this program to work with the UNmodified Wii nunchuck? I am about 2 weeks of stuff away from attempting it myself, but I'm still working on some other fabricating. I'd like to be able to control the steering by using the accelerometers in the nunchuck but the other (excellently written) instructable is set up to export the accel readout as a varible voltage to feed to another microporcessor instead of directly into the code to the motor controller. Didn't want to reinvent the wheel if it wasn't needed.

BTW, Thanks to all for all the support so far. It's funny that the more DIY stuff I do the more I feel the support comes from so many others. I a very big way, none of us do anything entirely on their own :)