PIDDYBOT – A Self Balancing Teaching Tool

We’re sure that most Hackaday readers are already familiar with the inverted pendulum system, which basically consists of a pendulum having its center of mass above its pivot point. Most applications (like the one we are going to describe) limit the pendulum to 1 degree of freedom by affixing the pole (or circuit board here) to an axis of rotation. The overall system is therefore inherently unstable and must be actively balanced in order to remain upright.

[Sean] created the piddybot, a tiny balancing robot aimed to teach the basics of PID control by trying to get the robot to stand still. More interestingly, the Proportional / Integral / Derivative values can directly be adjusted using the three on-board potentiometers. This will allow users to get the feel of each parameter’s impact on the robot behavior. The piddybot is based around the Arduino nano, a custom PCB, 2x 26:1 geared motors, one 1A dual motor driver board, a six degrees of freedom Inertial Measurement Unit, 2 batteries and finally a 3D printed body. You can check out a video of the robot in action after the break.

This project stems from a non-PID self balancer which [Sean] hacked together in September.

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Kitchen Hacks: Improving an espresso machine

The heat sensor in [Cameron]‘s espresso machine doesn’t work very well. He sees some pretty crazy variations in temperature when pulling an espresso shot, and when the boiler is just sitting there the heater element will heat the water full-bore then shut off for a while. Since this is a pretty low bar from a control theory standpoint, [Cameron] decided on a PID makeover on his espresso machine.

Instead of going with a commercial PID controller like we’ve seen on a few kitchen hacks, [Cameron] decided to roll his own Arduino derivative based on an ATMega328 microcontroller. The newly designed board reads the state of the ‘Steam’ button, a few relays for controlling the heater and the pump, and of course an LCD display.

[Cameron] still has to do a little tweaking to get his PID algorithm down, but already the new control board keeps a much more stable temperature than the old thermostat. The fancy new bezel and LCD display adds a lot of techy class to his espresso machine, to boot.

Silvia PIC controlled PID looped Espresso Machine

Last night I rebuilt my ECM Giotto with a new boiler. I’ve seen PID controlled machines before, but today I stumbled across this modded Rancillo Silvia. [Tim] replaced the internal brain with a PIC controller, added a NES control pad for input, a VFD display and a custom laser cut acrylic top. He used the PIC to provide PID control and PWM heater control with the usual solid state relays. I was leaning towards using a PIC for PID control myself, but then I scored my Giotto. (The heat exchanger and larger boiler makes it a bit of a moot point, but I’m still tempted to add PID boiler controls.)