Easy Power Supply Mod Takes Control

Inexpensive bench top power supplies are great for the home hobbyist, featuring wide voltage range and current limiting for a low price. What’s not to love? The controls; most have a single-turn pot that is typically very fidgety, especially at low voltage.

The solution is to replace the factory pots with nice wire-wound 10 turn units in order to gain 10x the precision. Of course nothing is ever drop in, the new pots didn’t fit the old holes, but that is nothing a few moments with a drill can’t fix. Also the original knobs no longer fit, but that’s just an opportunity for a knob upgrade.

The end result is still a power supply with fidgety controls, but instead of holding your breath, tippy tapping knobs to get within 100mV of your target, you can dial right in to within 10mV of your target. That makes life much easier, especially on low voltage projects that may not have power regulation quite yet.

Join us after the break for a video with all the info.

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Heating Up a Printrbot’s Bed

A heated bed for the Printrbot 3D printer

Heated beds for 3D printers help reduce the amount of curling and warping of parts. The warping happens when the part cools and contracts. The heated bed keeps the part warm for the entire print and reduces the warping.

As an upgrade to her Printrbot, [Erin] added a heated bed. The first plan was to DIY one using Nichrome wire, but heated beds are available at low cost. They’re basically just a PCB with a long trace that acts as a resistor. She added a thermistor to monitor temperature and allow for accurate control.

The Printrbot heated bed worked, but didn’t heat up quite quick enough. [Erin] was quick to scratch off the solder mask and solder new leads onto the board. This converted the board into two parallel resistors, halving the resistance and doubling the power.

This version heated up very quickly, but didn’t have a steady heat. The simple control that was being used was insufficient, and a PID controller was needed. This type of control loop helps deal with problems such as oscillations.

The Printrbot’s firmware is based on Marlin, which has PID support disabled by default. After rebuilding the code and flashing, the PID gains could be adjusted using g-codes. With the values tuned, [Erin]’s printer was holding steady heat, and can now print ABS and PLA with minimal warping.

Toddler computer remote

[Killerdark] has built a simple remote for his toddler to control videos on a PC. He gutted a USB number pad, built a new enclosure with the necessary buttons clearly labeled, and mapped the buttons in software.  He could have possibly done better with larger color coded buttons, but really, it seems to work well as is. This reminds us of the giant iPod remote from back in 2006. Good job [Killerdark]

Wii Fit Balance Board controls robot


More Wii Fit Balance Board hacks keep rolling in from Europe. We’re not sure we agree with [Juan Gonzales]’s assertion that the Wii Fit Balance board is the best way to control robots, but we can’t deny how fun it looks. [Gonzales] managed to control a robot of his own design with the balance board, making it turn when he leans to the sides and moving forward and back when he leans in those directions.

The robot, which he calls SkyBot, is fairly impressive in its own right, built from a PIC microcontroller and featuring various infrared sensors and 6 contact sensors. The robot’s OS can be controlled from Windows, OS X, or Linux, but for this project, they used Debian. The balance board interfaces with a laptop connected to SkyBot; custom software (tar.gz file) to make this work was written in python, and is available on [Gonzales]’s robot wiki, as well as instructions on how to build a SkyBot. It is in Spanish, however, so fire up Google Translate and get to work.

[via Balance Board Blog]