Hacklet 74 – Well Balanced Projects

Balance: we humans take it for granted. Without the sense of balance provided by our inner ears, we would have a hard time standing or walking around. What’s easy for us can be very hard for machines though. Projects that balance things have long been a challenge for engineers, makers and hackers. And rightly so, as building a machine to keep an object in balance often requires some novel electronic and mechanical solutions. This week’s Hacklet is all about projects that keep an object – or themselves – in balance.

wheelWe start with [Manuel Kasten] and Balance Wheel. Inspired by a project at Chaos Communication Congress, [Manuel] created a hack that looks timeless. A stainless steel ball is balanced on top of a wooden wheel. The system detects the ball’s position using a solar cell. More light on the cell means the ball is slipping off the wheel. The system counteracts this by spinning the wheel to oppose the falling ball. In the old days this would have been an analog system. [Manuel] made things a bit more modern by using an ATmega644p processor. The video shows the wheel spinning a bit fast, as the system was tuned for a ping pong ball rather than a heavy steel roller.

sidewayNext up is [Jason Dorie] with Sideway. Sideway is a two-wheeled skateboard that self-balances. One of the best parts of this project is that most of the mechanical components are from electric scooters, which means they are easy to source. The frame is even easier: A solid piece of plywood supports the rider and all the electronics. Two scooter motors are driven by a Sabertooth 2x32A motor controller. A Parallax Propeller performs the balancing act, obtaining IMU data from an ITG3200 digital gyro and an ADXL345 accelerometer. Speed is controlled by leaning forward and back, like a Segway. Steering is controlled by a Wiimote nunchuck. Sideway is powered by 3 cell LiPo batteries. [Jason] says this ride gets a lot of attention every time he takes it out.


balance-robot[Dominic Robillard] developed his Stair-climbing self-balancing robot as part of his masters degree at the University of Ottawa. We don’t know what grade his advisors gave him, but we give this project an A+. The robot is a 4WD off-road monster. Two heavy-duty drive motors give it tank style steering. The most impressive part of the robot are the two arms which allow it to roll its entire chassis up and over obstacles which would stop much larger robots. [Dominic’s] robot isn’t just statically balanced though – it can rear up and ride on two wheels Segway style. If it does tip over, the arms will lift it right back up!


terrabalanceFinally, we have [Paul Bristow] with Terabalance. [Paul] got his hands on an early copy of the TeraRanger One, a Time of Flight (ToF) sensor developed at CERN. He decided to test it out by using it to balance a ping pong ball on a wooden bar. The sensor had to be slowed down quite a bit in this application, data is only read about 1000 times a second and averaged. An Arduino reads the distance data from the sensor and uses that data to drive a hobby servo. No PID loops here, in fact, Terabalance is a great example of how a proportional only system will hunt forever. That said, it is good enough to keep the ball on the balance bar.

There are a plenty of balancing projects on Hackaday.io. If you want to see more, check out the new well balanced project list! Did I miss your project? Don’t be shy, just drop me a message on Hackaday.io. That’s it for this week’s Hacklet, As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

Two Wheeler is Gyroscope Stabilized

[Jim] loves gyros – not those newfangled MEMS devices, but old-fashioned mechanical gyroscopes. His obsession has pushed him to build this gyro stabilized two wheeler. We love watching hacks come together from simple basic materials and hand tools, with liberal amounts of hot glue to hold everything in place.  That seems to be [Jim’s] philosophy as well.

This is actually the fifth incarnation of [Jim’s] design. Along the way he’s learned a few important secrets about mechanical gyro design, such as balancing the motor and gyro assembly to be just a bit top-heavy. [Jim’s] gyro is a stack of CDs directly mounted to the shaft of a brushed speed400 R/C airplane motor. The motor spins the CDs up at breakneck speed – literally. [Jim] mentions that they’ve exploded during some of his early experiments.

The gyroscope is free to move in the fore-aft direction. Side to side balance tilting is on the wheels themselves. The wheels are model airplane wheels, which have a curved tread. No cheating by using flat LEGO wheels in [Jim’s] lab! A potentiometer measures the tilt angle of the gyro. The voltage from the pot is fed into an Arduino Uno which closes the loop by moving a servo mounted counterweight.

The vehicle is controlled with a regular R/C plane radio. A servo steers the front wheel while another DC motor drives the rear wheel. Not only is [Jim’s] creation able to balance on its own, it can even make a U-Turn within a hallway.

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Building an accurate equal arm balance


This interesting take on weights and measures uses a two foot long level as the base for a diy equal arm balance. The balance is the oldest method used for measuring mass. That’s because you don’t even need a reference weight for it to work as long as you are measuring ingredients that are proportional to each other in whole numbers.

The key to accuracy with these scales is to reduce friction at the fulcrum. In this case the fulcrum is made of two upturned razor blades on the base, with a single razor blade resting perpendicular to those on the arm. But because gravity is doing the equalization, the base must be as level as possible. Adjustable feet were added to the base so that it can be leveled on two axes. When the tower at the center was built (using threaded rod) a disc level was used to fine-tune the mounting angle of the two razor blades. The finishing touches include a coupling nut on each end for fine-tuning the balance, and the halves of a tea ball strainer as the weighing vessels.


This cube is made for walkin’


Meet Cubli, a research project which aims to make a cube that can walk around without using any appendages. It’s a research project at the Institute for Dynamic Systems and control in Switzerland. Anyone else thinking about our beloved companion cube right now?

The robotic experiments are based on angular momentum. Inside of the cube there are center mounted motors which each spin a wheel. Three of these are mounted perpendicular to each other to give the cube the ability to change its position along any axis. This is best shown by the first video after the break where just a single side of the assembly is demonstrated. A square frame starts at a rest position. You see the wheel spin up and it is suddenly stopped, which causes the momentum of the wheel to pop the square frame up onto one corner. The wheel then switches into a second mode to keep it balancing there. The final mode is a controlled fall. This theoretically will let the cube move around by falling end over end. So far they’re not showing off that ability, but the second demo video does show the assembled cube balancing on one corner.

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Printing and programming a self-balancer

The Hackaday staff isn’t in agreement on 3d printers. Some of us are very enthusiastic, some are indifferent, and some wonder what if they’re as widely useful as the hype makes them sound. But we think [Jason Dorweiler’s] self balancing robot is as strong a case as any that 3d printing should be for everyone!

Don’t get us wrong. We love the robot project just for being a cool self-balancer. Seeing the thing stand on its own (video after the break) using an Arduino with accelerometer and gyroscope sensors is pure win. But whenever we see these we always think of all the mechanical fabrication that goes into it. But look at the thing. It’s just printed parts and some wooden dowels! How easy is that?

Sure, sure, you’ve got to have access to the printer, it needs to be well calibrated, and then you’ve got to make the designs to be printed out. But these hurdles are getting easier to overcome every day. After all, there’s no shortage of people to befriend who want nothing more than to show off their Makerbot/RepRap/etc.

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The bicycle can tell us how to make it better

Over the years bicycle design has changed. Materials were upgraded as technology advanced, and accumulated knowledge helped bicycle builders make improvements along the way. But deep analysis with the intent to make meaningful improvements has not been widely embraced. Reasearchers at UC Davis are looking to expand into this frontier by letting the bicycle tell us how it can be improved. This is one of the test bikes they’ve been working on, which is mainly aimed at data harvesting. They’re hoping to find some real improvements based mostly on how the machine can get out of the rider’s way as much as possible. The thought here is that the rider’s body makes up 80-90% of the volume of the vehicle and should be accommodated in every way possible.

Sure, this could be a case of trying to build a better mouse trap. But listening to the discussion in the video after the break really drives home the complex issues of stability and locomotion that go into these seemingly simple vehicles. We’re going to guess the final recommendations will not involve making the bike five times taller.

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Android legs stability testing

This is [James’] latest android build, a set of legs that use gyroscopes for balance.

He started off by planning the build with some LEGO pieces to get an idea of how each foot and leg joint would fit together. This let him achieve one of his goals. From the start he wanted to create a robot that would remain stable, and not build up enough momentum to tip itself over if there is a problem. With the dimensions established he cut out parts from 2mm sheets of HIP plastic using a hobby knife. They work in conjunction with a frame made from aluminum and HDPE. The whole thing houses eight servos responsible for movement, but he found an interesting way to use them for balance as well.

[James] came across some gyroscopic sensors which are made for use with RC helicopters. They connect in-line with a servo motor and offset it based on the gyro data. He’s using four of them with this bot, playing the hip and ankle servos against each other for balance. What results is a set of legs that look like their jonesin’ for a fix. See for yourself in the clip after the break.

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