Picture of Balancing Robot
Robot 3.JPG
Robot 2.JPG
Robot 1.JPG
This is a very simple robot that uses a simple switch as a sensor and stands on only two wheels with inverted pendulum mechanism.
When the robot is going to fall the motor starts and moves the robot to the direction it is going to fall, so the motor torque about the center of gravity that is higher than the motor makes the robot balanced.

Step 1: Things you need

To make this robot you need following parts and tools:
small electric motor
some gears
(or a motor with gearbox)
a shaft
two wheels
some sheets of plastic to make bearings and the robot neck
two battery holders
4 AA batteries
one button cell
one SPDT (single pole double throw) switch with a metal lever
one toggle switch for the on/off switchs
one nail
some wire
soldering iron
some glue
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bolanka1 month ago

Thanks.. I made it.

Arthak7 months ago
how can I make that switch
vahid_you2004 (author)  Arthak7 months ago
You can buy a switch with lever or find some without lever in a dead computer mouse and attach it a lever.
Arthak7 months ago
best use of brain
maker_studio9 months ago

The easiest Arduino UNO based self-balancing robot, controllable by Smart Phone, RC and more!


The problem isn't the center of gravity, it's stability. The switch will work as a measurement device so long as the robot is VERY close to vertical. If you get much past that narrow threshold, the robot doesn't add more torque to the motor to compensate. If you want it to be more stable, you'll have to use some analog device to measure the tilt-angle and another circuit to control motor torque through input voltage. A simple sensor would be a multi-turn potentiometer.
Another possibility for variable torque control, more in the spirit of the author's design, would be to add two additional switches (one for each possible direction of fall), arranged to turn on only when the robot gets closer to the horizontal on that side. Each of these switches would add an additional battery into the circuit in series. Then the robot would be carrying six or even eight batteries. As a bonus, the additional weight of the batteries might actually help it work more smoothly.
vahid_you2004 (author)  ERockDesigns5 years ago
You're right.

High CG object has high moment of inertia, so it needs more moment to move and has more stabillity. Because of these you must choose the longest robot and consider your motor power.

The more complex controlling system, the more stabillity. but the most important feature of this robot is that it is simple (according to the the others comments)
dratman1 year ago
This is a wonderful, excellent project. The approach is exactly what one wants from a first build of any new device: the simplest possible implementation, with the loosest possible tolerances and the most room for experimentation to make the device work, and then to improve it.
jestela1 year ago
good day buddy! can I use this experiment for our science investigatory project? please, I'll give a credit in return. Please :/
vahid_you2004 (author)  jestela1 year ago
Yes, of course you can.
wcallag2 years ago
I've been trying to find those gears!!! Where did you get them??
vahid_you2004 (author)  wcallag2 years ago
nmvb2 years ago
why is the switch in between the battery packs instead of after?
vahid_you2004 (author)  nmvb2 years ago
Because it must control the current to flow to the motor, so it must be before motor.
nmvb3 years ago
what is a roller on the SPDT switch? does it matter if this has one?
vahid_you2004 (author)  nmvb3 years ago
roller causes the switch move on the ground perfectly, I recommend to attach a simple roller to your switch or use a switch with roller.
David974 years ago
I built one of these and my one doesn't tip over. It is about 11 cm in height. Also mounting the switch out further from the axel helps it is 1.5 cm from axel from the cloest edge on switch. Hope this helps to get your one working well.
Aso it is a good idea to have the hight of switch adjustable. As I spent 2 hours adjusting the hight.
vahid_you2004 (author)  David974 years ago
Good idea, by an adjustable switch you can make robot standing on a steep too.
Could you upload a video of your robot, it would be very helpful for ones who want to make one.
AlKaswa5 years ago
where would i find a single pole double throw switch
vahid_you2004 (author)  AlKaswa5 years ago
Electronic devices shop
 aka radioshack

ive also pulled one out of a computer, and several other interesting looking switches. mostly out of the optical drives, front panels and a somewhat of floppy drives, but if you keep your eyes open...
I've also noticed that radioshack has accelerometers. I wonder if you could use those too? Might be more arduino based than BEAM though....
try the buttons from mouses. they are conveniently SPDT, (not needed) but they have no lever, i've been able to fashion ones from paperclips and other simple materials.
TigrisLi4 years ago
Where did you get the wheel with the shaft??
vahid_you2004 (author)  TigrisLi4 years ago
A toy!
ok, thanks!
Add a second sensor, the motor wont work as hard, and it will stay balanced longer.
tobyscool4 years ago
i made the hugest mistake i shorted the batteries EPIC FAIL so my battery bursted
Exocetid5 years ago
This robot is great and I really like how you did the position sensor, extremely clever and what "Instructables" is all about. That said, you might want to change the switch on your sensor, which basically just gives you "Bang-Bang" control and hence the instability, to a potentiometer or variable resistor. That may involve putting an amplifier in there, but we EE's have been allowing ME's to use electronics for quite some time now ;-) (mechatronics)
vahid_you2004 (author)  Exocetid5 years ago
Good idea. I like mechatronics a lot.
It seems to me that the center of gravity is high which causes the robot to have to react faster than it is capable of due to the circuitry delays, inefficiency of the wheels to move as quickly as needed.

I have two Segways (a blast, by the way) and they stand up on their own. It's fun to watch them "dance"..

I literally had to go to the factory in NH to take a class on how to ride these models. Yes, long time ago.

What they suggested this: to stabilize my units when first riding it, add some weights to the saddle bags on either side. It not only helped me when learning, it helped the Segway stay upright without excess movement

So what I'll seggest (lol) to you is this: get the center of gravity lower by moving the batteries down or adding weight to the bottom of the plastic. That should allow the bot to stay upright without falling over.


Grand Rapids, MI
 Thats really cool and a good idea, and i have an alarm clock like that, it has a very dense material on the bottom with a rounded edge, so to turn it off u just push it back, then it pops back up.

but why do u have 2 segways, its pretty cool, i just dont understand y u have them.
Originally, I bought the two Segways for advertising purposes.

My intention was to hire good looking college gals to ride them around with our company logo on the side of the saddle bags, answering questions about our business and handing out literature.

Great marketing idea, but have not had enough time to devote to the project.
Robot Lover5 years ago
  I like this. Reminds me of my youth, building a line following robot with a car battery and two window regulator motors from an old Lincoln.
  It would be interesting to try it with tilt switchs (**MERCURY is BAD kids**) and perhaps make two stages of power, voltage divider between cells for those times when it tilts beyond a certain range the additional voltage is switched on.
  Also would be neat to try a magnetic pendulem with reed switchs.

Good Job.
but you would need a spdt tilt switch... i think this switch is better because of its immediate response and its adjustable. You can't adjust the force of gravity on the tilt sensor...
Mercury is Cool !
it's true.
ratgod5 years ago
Thats pretty good considering their is no microcontroller doing the balancing, its a neat simplistic design.

excellent instructable.
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