What makes a project really exceptional? Part of it is a, ‘gee, that’s clever’ angle with a little bit of, ‘that’s actually possible.’ One thing the Hack a Day crew really appreciates is awesome enclosures. Altoids tins will get you far, but to step up to the big leagues you’ve got to bend some aluminum. Luckily, [Rupert] sent in a great tutorial on bending aluminum sheets for enclosures.
To make his press brake, [Rupert] scavenged a few pieces of 38mm bamboo worktop scraps. After assembling a few of these pieces with some hinges, he was ready to bend some aluminum.
One trick [Rupert] picked up is scoring the sheet metal on the inside of a future bend. For [Rupert]’s project, he sent his 3mm aluminum sheet through a table saw set to cut 1mm deep. Of course this should only be done with a blade designed for non-ferrous metals with as many carbide teeth as possible. Judging from [Rupert]’s homebuilt Hi-Fi that used this construction technique, the results are phenomenal.
Here’s a nice little circuit that will drive a motor and allow you to stop its rotation, giving your robot a set of brakes. It’s part of [JM’s] post about the in’s and out’s of building microcontroller friendly motor controllers (translated).
This particular setup is a half H-bridge. It allows you to drive the motor in one direction only. The MOSFET used on the ground-side of the motor doesn’t actually need to be there. This is the brake which let you electronically stop the motor from spinning. Without it, the motor will keep turning under its own momentum when the half-bridge is shut off. Depending on the application this can be a big problem. There’s a great demonstration of the circuit braking a fast spinning motor in the video clip below the fold.
It is possible to use this driver with PWM, but [JM] has some warnings about inbuilt functions like FastPWM. Make sure you read his admonition, and if you need a refresher don’t miss this Hackaday video segment.
Continue reading “Motor drivers: half h-bridge with brake and more”