Introduction: SciChair (Balancing Electric Chair)

Picture of SciChair (Balancing Electric Chair)
One day whilst at work we decided we would build something cool so we went to the Instructables website for ideas! Our criteria was that it had to be driven by an Arduino! After searching through the vast amounts of really cool projects, we found XenonJohn's Balancing Electric Skateboard  

We thought we should build a stand-on Balancing scooter but then decided that we needed to make something original. What about a Balancing chair my boss said. Now that's cool!

We happened to have a cool looking Carbon Fibre Racing chair just sitting around not being used so we started with that. We previously ordered a couple of geared down 250W scooter motors and some wheels to suit.

Now to order the electronics! Reinventing the wheel is a waste of time, and XenonJohn had already developed the code and worked out which hardware to use so we ordered exactly what he recommended.

Power came from some Makita drill batteries. These are used for most of our travelling exhibits as they are easy to get, to charge and we have a few batteries laying around for just such a purpose.

Here is a short video of the chair being driven around. Note the 3rd build Balancing scooter too doing a drive through.

















Step 1: Description of the Build

Picture of Description of the Build

The description of this build a little bit in reverse as we built the chair fairly quickly and forgot to take build photos.

There is little or no detail about the balancing software or how it works as XenonJohn has already described this so well.
There will be details on how we built our SciChair and what you will need to do to build your own.

The electronics is nearly exactly what XenonJohn used on his skateboard but I have removed the resistors he used for the switches so therefore, the code is different. See attached code for button steer and proportional steer.

Step 2: Parts

Picture of Parts
Parts Needed:
  • Chair - Any type will do. Something comfortable that you can lay back into.
  • Arduino UNO - Check your local suppliers or eBay.
  • Sabertooth 2x52 Motor Controller- www.dimensionengineering.com or a local supplier.
  • 5 DOF accelometer www.ebay.com/itm/181004141876?sPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
  • 2 scooter motors - I would recommend 200w and up. www.oatleyelectronics.com or eBay. Have a look around your area.
  • Batteries - SLA batteries are good and cheap, Power drills can be quite inexpensive too.
  • Wheels - Larger wheels are better for bumps. Get one with the same sprocket chain type as the motors if possible.
  • We got our wheels from www.oatleyelectronics.com
  • Shielded multi-core cable for the accelerometer and heavy power cable for the motors
  • Deadman switch
  • Toggle switch for turning. A joystick is good for this.
  • Toggle switch for adjusting balance position.
  • DC connector for Arduino.
  • DIL pins to suit Arduino
  • Double sides tape
  • Screws etc 
  • Metal tubing for the frame

 







Step 3: Tools

Picture of Tools
Basic tools are required.
Also,  you will need someone with the equipment and skills to weld the frame.

Other tools you will need:
  • Drill and drill bits
  • Soldering iron and solder
  • Wire cutter and wire strippers
  • Heat shrink and hot air gun to shrink it

Step 4: Building the Frame

Picture of Building the Frame

The design of the frame is quite basic (see photos).

There is a U-shaped tube over each wheel to bolt the wheel to and to hold the motors, and a bar between these as the main member. At first we didn't have the gussets in place (triangular shaped pieces) but the bottom bar started bending. Make sure that the main member is heavy duty and have reinforcing to the wheel U shape.

Then add a central tube for the two removable skids. Skids are recommended because they stop a lot of breakages and accidents. We made the seat mounts adjustable for a balance point but this is not needed. Just mount your seat in the middle.

We used a Carbon Fibre Racing Chair we just had sitting around, but most people don't. Try a school seat, car seat or whatever you can find that's comfortable and has a long back with head rest, if possible.



Step 5: Motors

Picture of Motors

The motors we used are geared 250W 24V brushed motors from www.oatleyelectronics.com
Motor RPM is about 320 RPM.

The wheels were purchased from the same place.
The fine tooth gear was removed from the wheel and a BMX gear was fitted on the thread.
The pitch of the BMX gear was the same as the motor 12.7mm.

Although this works okay, there is a bit of chain stretch and the key way on the motor gear will wear out eventually.
It is better to use toothed belts here, if possible but the cost does go up when using these!

A plate was made to hold the motors and it bolts to a piece of metal welded to the frame. The piece of metal has two slots cut into it to allow the motor to slide up/down to take up the chain slack. There are different ways of doing this. Something like how a car alternator mounts might be another way. Open the bonnet of your car and see how it's done.


 

Step 6: Electronics

Picture of Electronics
The electronics section involve three things: Mount the motor controller and ardunio somewhere where they won't get damaged when you crash! Yes you will crash!!!!!!!!!

The Accelerometer needs to be mounted preferably at axle height and vertical. The four holes on the circuit board should be facing down and the chip side to the back.

We used double sided tape as it's a good insulator and sticky!!!!!!! Make sure it's in a nice waterproof area and maybe even heat shrink it water tight. A glue coated heatshrink is good for this. We used shield cable for the wiring as it will stop any added noise getting into the system.

Make sure it is held on tight. If not you will have a bucking bull chair! Believe me I know about this!

The unit has a few switches to add.
  1. The dead man switch. The big red button that has to be held at all times to make the unit work.
  2. Main Power. Cuts power to everything. Ours was built into the battery holder.
  3. Joystick. Allows you to turn left/right and drive forward in up coming code.
  4. Tilt Adjustment. Allows you to adjust your balance point

Find a good safe, easy to use spot to mount these. Connect all units together and wire these up as per the wiring diagram.
The wiring is pretty much the same as Xenonjohn's Skateboard but without the resistors.
See our circuit diagram below.

Once it is all wired and the code has been uploaded, it's time to test. Puts ome bricks underneath it to lift the wheels off the ground. Tilt it forward and turn the main switch on. Wait your four seconds for the Acceleromoter to calibrate and hold down the deadman switch. The wheels shouldn't start yet.

Slowly tilt the unit back until the Accelerometer is vertical. The motors should start up and you should be able to slowly move it back and forward to slow and speed them up. Check the rotation to make sure that the wheels are going the right way. If not, then power the unit down and swap the polarity for that motor.

Now, you should be ready to drive the unit around.
 

Step 7: The Code

Picture of The Code

The main code used is XenonJohns code for his skateboard. I used the rocker steering but we removed the resistors.

So here is the code for toggle button steering but still using your tilt for forward/backward movement.

**************************************************
Code bug updated on the 24th Feb 2012.
Issue with timing routine.
**************************************************

Step 8: Videos

The SciChair in action!

Step 9: New Features (Pot Steer and Code)

Picture of New Features (Pot Steer and Code)

************************************** New features added 24 August 2012********************************************

Well, we finally have some new features.

We have fitted a potentiometer joystick with proportional steering.
Also the forward/backward movement is still done by Joystick control too.

We have added two Li-Ion batterys instead of the single battery.

We added a status light for the gyro startup period.

And BLING. We added a strip of blue LED's underneath to make it look cheaper.
Nothing better than adding a blue LED to something to make it look cheap!

THE CIRCUIT:
We have removed all the resistors and used software pullups for ease of building.
See the circuit diagram in the pictures above.

THE CODE:
I have also posted the Code below for proportional steering but uses lean to move. The deadman switch has a lock-out, so if you release the button then you need to completely power the unit down and go through the whole start-up procedure again. (For Safety reasons)
It also has a light that flashes when you turn power on until the gyro locks on (about 4 seconds).

FUTURE CHANGES:
We will be changing the chain drive to timing belt drive. (See the expanding collets in the picture above)

Pictures coming soon!

Comments

ScitechWA (author)2012-02-13

Hi Everybody.
Thanks for your patients waiting for the code.
Well it's finally here!
Both the switch steer and the resistor pot steer.
Wiring is quite easy. I have a simple diagram to show what goes where.
Enjoy and let me know if there is anything missing or questions.

XenonJohn (author)2016-08-26

Have you noticed this has now been copied (too) in China?

It is one of those hoverboards with a seat stuck on top essentially. Described as self-balancing so the nose wheel is just for starting and "landing" I assume. The levers twist each half of the hoverboard instead of doing it with your feet.

TruongT9 (author)2016-02-14

How i do it work with 6DOF Digital IMU MPU 6050 (

http://42bots.com/tutorials/arduino-uno-and-the-invensense-mpu-6050-6dof-imu/ )

EricD56 (author)2015-12-11

they are out of the 5DOF accelometer. will a 6 DOF work with the same code??

dbulat (author)2015-04-18

hello sir can i ask u in the diagram 12v battery working for 1 motor or both?? coz im using 1 12v 7.5ah SLA battery since in malaysia its the cheapest i can get..and can i know will it working when the IMU im using is 3dof ADXL345 thx

syedtanzeem (author)2015-02-17

Will this work without the 5 dof accelerometer? I will be implementing 3 wheels so self balancing is not required.. Should I make any changes in the codes?? Please help.. Thanks..

syedtanzeem (author)2015-02-17

Hi I'd like to implement this idea in my project viz basically an automatic wheelchair. I can exclude the gyro sensors and only implement the motors, driver and the joy stick right ? help is appreciated thanks :)

Caterg (author)2014-11-14

Hello, ScitechWA, I do not understand electronic and 5dof for Brazil is impossible to achieve. Would it be possible to post the code for the 6DOF IMU Gyro 6050? Thank you for your attention. As you can see in the photos, positioned inside the engine, and I'm using a larger wheel.

jake.penney.7 (author)2014-09-08

hi guys.

i build the scichair but when i go to program the arduino it says that 'the keyword BYTE IS no longer supported'

how do i fix this ?

it is in the code line

SaberSerial.print(0, BYTE); //kill motors when first switched on

}

ScitechWA (author)jake.penney.72014-09-08

Download the earlier version of arduino program Version 0023

Maksvl (author)jake.penney.72014-09-08

You are faced with the same problem as me.

A few posts below, I also asked about it, the reason is the version, this code only works with version 0023.

if you want ispolzovat recent version 1.0 and above you will have to spend a recoding, I now work with version 1.5

here everything is clear described https://decibel.ni.com/content/thread/11196?tstart=0

Maksvl (author)2014-09-08

Good afternoon. Collected on your grand project, there are several issues.

Why and when the authorization gyroscope impossible immediately command the movement or rotation of a joystick. Joystick it starts listening only after a small inclination.

And why the team to retain the balance comes slightly inert (in my opinion), although it is perhaps because I put on a very experiments and a small prototype. And hold the balance or does not work. I tried already to increase value to 1 (float aa = 0.005; // this means 0.5% of the accelerometer reading is fed into angle of tilt calculation with every loop of program (to correct the gyro)) but rvno balance is not maintained.

Thanks in advance for your answers.

ScitechWA (author)Maksvl2014-09-08

Hi,
Thankyou for your comments.
All code is an "as is" basis.
We copied the code from another project. "Balancing skate board."
So we did not write the code. We did some changes.

The code works for us fine.

Check your gear ratio. Too high will not allow you to balance.

Maksvl (author)2014-06-04

Produces here such errors

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp: In member function 'void SoftwareSerial::begin(long int)':

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp:396: error: 'PCICR' was not declared in this scope

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp:399: error: 'PCMSK2' was not declared in this scope

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp:399: error: 'PCMSK0' was not declared in this scope

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp:399: error: 'PCMSK1' was not declared in this scope

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp: In member function 'void SoftwareSerial::end()':

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp:414: error: 'PCMSK2' was not declared in this scope

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp:414: error: 'PCMSK0' was not declared in this scope

C:\arduino-1.0.2\libraries\SoftwareSerial\SoftwareSerial.cpp:414: error: 'PCMSK1' was not declared in this scope

ScitechWA (author)Maksvl2014-06-05

Use version arduino-0023.
That will fix those errors.

Maksvl (author)ScitechWA2014-06-05

Sorry for my English is not clear.

Thank you very much, I tried running without errors.

What do you think the account conversion here this way?

https://decibel.ni.com/content/thread/11196?tstart...

ScitechWA (author)Maksvl2014-06-05

Yes if you convert those codes it should work.

Just as easy to download the old version.

Maksvl (author)2014-06-04

Which version of the Arduino sketch written? When compiling an error.

This one will be right for a gyro? http://www.ebay.com/itm/5DOF-module-accelerometer-and-dual-axis-gyro-instrument-IDG650-ADXL335-/261488421936?pt=LH_DefaultDomain_0&hash=item3ce1ecac30

austiny6 (author)2014-02-17

Hi. I am building my own SitWay and I think your components and codes are great.

The IMU link you provided is a blue accelerometer that is way more expensive than the red one you have in the image which is around 15US. Should I order the red one? In addition, I have a Triple Axis Accelerometer & Gyro Breakout SEN-11028

do you think I can use your code directly for that?

I am a high school student and am very eager to finish this project in time. Thank you

ScitechWA (author)austiny62014-04-16

This IMU will not work with the code.
It's a digital IMU and the code is for an analog one.

heath_kerr (author)2013-12-23

Making life easy,ha

_Rommel_ (author)2013-10-03

Hello, how much RPM for my motors is recommend?

Maksvl (author)_Rommel_2013-10-09

The specification is specified as 320 revolutions per minute

Maksvl (author)2013-10-07

The documentation pdf file is not correctly specified the polarity of the battery.
You wrote about the blue LED that blinks for about 4 sec gyro calibration. But I did not find it on a map.

Maksvl (author)2013-10-06

I apologize for the error - I write through a translator.
Maybe someone else is looking for an analog gyroscope.
Here's the link itself today already ordered a 2 piece
http://www.aliexpress.com/item/5DOF-axis-analog-gyro-sensors-module-IDG500-IDG655-IDG650-ADXL335-module/578668074.html

ScitechWA (author)Maksvl2013-10-06

nice find

Maksvl (author)Maksvl2013-10-06

Why then the link does not want to be inserted
aliexpress.com/item/5DOF-axis-analog-gyro-sensors-module-IDG500-IDG655-IDG650-ADXL335-module/578668074.html

_Rommel_ (author)2013-09-27

Yesterday i ordered all parts for my self-balancing scooter project, but the code i think to get from here and the joystick function as well. Sometimes when i dont want to tilt forward/back ill use the joystick.

ScitechWA (author)_Rommel_2013-09-30

Yes the code can be used by leaning forward/backwards or using the joystick.

fredbana (author)2013-08-19

thank you sir for quick respond

fredbana (author)2013-08-18

are you useing 5k pot? for steering?

ScitechWA (author)fredbana2013-08-18

5k or 10k It's used as a voltage divider.

TheVenueManager (author)2013-04-29

Hi ScitechWA,
Well my boys and I are embarking on a build based on your SciChair...we have purchased all the items including the 5 DOF accelometer (linked to in the parts list) and can't seem to work out how to wire this in to the circuit based on the different board layout. Can you provide some guidance on this...

We live in Adelaide and hope to have our self-balancing "cockpit" up and running in a few months...we would also love to send some photos and perhaps video when we finally get things sorted.

Thank you for all the info in your instructable, it seems pretty straight forward and gave us the confidence to embark on our journey :)

I'll have to draw up a new diagram for the new IMU.
But in the mean while if you look at the old sparkfun IMU and connect the same names as the new IMU.
The buttons on the joystick should connect to the tilt adjust mechanism.
I'll check it!

Can wait to see a video.

Also as a follow up question...I have had a look at the code and there does not seem to be anything addressing the forward and backward buttons of the joystick???

fozz18 (author)2013-04-19

is the code set to go slower than the segway-clone code you used?

ScitechWA (author)fozz182013-04-21

no it should be the same. Is thee an issue?

fozz18 (author)2013-03-28

how do I change the balance point? the annotations are not clear to me

ScitechWA (author)fozz182013-04-02

Do a search through the code for the value 350.
This value is in the annotation as 350 but the value I used in the code is 340.
Change it up/down by about 5 and this will change the tip start position.

ScitechWA (author)2013-03-26

Yep that's great. Works the same as the one we used but smaller.
The only issue is that bumps move your hand and the joystick more.

fozz18 (author)2013-03-25

got everything working tonight without changing your code. it was a loose wire causing my problem. What value potentiometer do you recommend the steering is super sensitive. I'm using 10k ones.

ScitechWA (author)fozz182013-03-26

That's awesome. I'll put the link up for that IMU.
We used a joystick that doesn't give full left or full right for the movement.
It's a 100k we are using but that doesn't matter as you put 5volts across the terminals and read the voltage from the wiper.
If you disconnect the gnd and 5volt lines and fit a 2k resistor inline between the gnd side and the 5volt side.
This means the reading will never reach 0volt or 5volts.
That should fix your issue.

fozz18 (author)2013-03-24

sorry to bother you but I have 5DOF module that I got from eBay and cant seem to get it working with your code any help would be appreciated I'm at a stand still here
http://www.ebay.com/itm/181004141876?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

ScitechWA (author)fozz182013-03-25

That's right that one won't work as it uses a different chip to the one we used.
We will be writting code for the 6DOF digital version soon.
John has written code for that IMU which it sound like you have.
https://www.instructables.com/id/Easy-build-self-balancing-skateboardrobotsegway-/step53/Code-for-use-with-new-6dof-DIGITAL-IMU-from-Sparkf/

Test it out and let us know how it goes.

gttipsgsegwayteam (author)2013-03-10

greetings sir,
what the value of potentiometer is used in the steering??

ScitechWA (author)2013-03-06

That's right the analog versions were nice and easy to read.
John who wrote the code we are using has done some code to use the IMU you have.
https://www.instructables.com/id/Easy-build-self-balancing-skateboardrobotsegway-/step53/Code-for-use-with-new-6dof-DIGITAL-IMU-from-Sparkf/

Let us know how it works.

bgoldberg1 (author)2013-02-20

Very cool looking! :)

It looks almost like a wheelchair for a disabled person, except for the smallish wheels.

Can it go up a curb from street to sidewalk?

ScitechWA (author)bgoldberg12013-02-20

lol. Except they don't use Carbon Fibre racing chairs. lol.
Nope won't go up curbs unless it's ramped.

bcamaro (author)2013-02-17

Please explain Why TORQUE = 9

ScitechWA (author)bcamaro2013-02-17

You might want to ask John that question.
He wrote the code.
https://www.instructables.com/id/Easy-build-self-balancing-skateboardrobotsegway-/

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