When brewing your own beer, temperature control is important. If the temperature isn’t regulated correctly, the yeast will be killed when it’s added to the wort. It’s best to cool the wort from boiling down to about 25 C quickly before adding yeast.
To do this, [Kalle] came up with a wireless temperature controller for his home brewing setup. The device uses a heat exchanger to cool the wort. An ATmega88 connected to a H-bridge controls a valve that regulates flow through the heat exchanger. It reads the current temperature from a LM35 temperature sensor and actuates the valve to bring the wort to a set point.
A neat addition to the build is a wireless radio. The nRF24L01 module provides a wireless link to a computer. There’s an Android application which communicates with the computer, providing monitoring of the temperatures and control over the set point from anywhere [Kalle] can get an internet connection.
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”
Tinywrench is [Tanjent’s] take on a motor controller board. It aims to replicate all of the functions that a standalone motor controller chip offers at as low a cost as possible. Early results are in. It works, and as seen can be assembled for about $8.
The top of the device offers a terminal block for connecting motors, ground, and 24V input. A pin header on the bottom has all the connections you would expect to find with a stepper motor driver board. Looking back on top there’s also a pair of ATtiny24 chips, each with its own trimpot for balancing the constant current output. Hiding on the underside of the board are two H-bridges built using high and low-side MOSFETs along with some diodes for protection, and various passive components for driving them.
As it stands, each of those H-bridges can handle around 9 amps which should be more than enough for projects with small motors. [Tanjent] mentions that one of the main advantages of working with this instead of a single motor-driver chip is that if you fry one of the MOSFETs you can replace it instead of trashing the entire board.
[Ed Rogers] has the unfortunate privilege of living right next to a set of train tracks, and as a man who holds his sleep in high regard, he needed to find a way to keep the noise in his bedroom to a minimum. To combat the sound of passing trains, he built himself a system that automatically closes his windows when a train passes by his apartment.
The setup relies on a web cam, which uses motion-sensing software to detect a passing train. The video is analyzed by a computer in his room which passes a message to an Arduino when a train is near. The Arduino then sends a pair of window mounted linear actuators into action, slowly (and quietly) shutting his windows.
The linear actuators move pretty slowly as you can see in the video below, but we doubt that matters. Since it looks like [Ed] lives in a slow zone, it likely takes quite a bit of time for a freight train to pass, making the 40-second closing period more than reasonable.
Continue reading “Motion detecting window closers keep train noise at bay”
[Petter] built himself a DIY Segway out of a couple of cheap electric scooters. We’ve seen a couple of very nice Segway builds in the past like the all analog Segway, or the creepy walking version, [Petter]’s Segway build seems like it would be a useful human transport device.
The motors, chains, gears, and wheels are scavenged from a pair of electric scooters. Steering left and right is accomplished by tilting the handlebars left and right. The handlebars themselves are attached to the joint at a base that allows them to be taken on and off. We’re thinking this would be great for throwing a [Petter]’s Segway in the trunk of a car – a design feature the original Segway doesn’t have.
Continue reading “DIY Segway recycles broken electric scooters”
So your electronic hobby skills are coming along quite nicely but you’re not very comfortable doing more than blinking a few LEDs. Now’s a good time to try something new by driving a couple of DC motors.
You probably know that you can’t just hook these up to the pins of your favorite uC and call it good. The motors draw a lot of current (especially if they’re strained in lifting a heavy load) which would burn out your logic circuitry. Add to this the excess induced current that is generated when a spinning motor is shut off and you’re going to need a control system that can handle these dangers.
Enter the h-bridge motor driver. [Chris] has guided us through the process of building and using a H-bridge in the past. This time he’s using a motor controller that has four half H-bridges built into it. He hooks up the SN754410 to two motors, giving him speed and direction control for both based on the duty cycle of a PWM signal entering the chip for less than $2.50. Check out the video after the break for an overview of his methodology, then work your way through the multi-page post that he recently published.
Continue reading “Intro to DC motor control using the SN754410”
Many a hacker has put together one of those cheap $30 robot arm kits you can get in just about any store with a section labeled, “science”. In an ongoing search for a cheap robot arm, [Larry] decided to modify one of them to be controlled with a PC through an Arduino. The article doubles as a really basic tutorial on dc motor control. On the site he gives a brief explanation of how to use H-bridges and a good explanation of how he wired them up for this purpose. He eventually goes on to add a processing interface to the project. The next step would be figuring out how to add some kind of position feedback, such as encoders. Though, if modifying an arm is not your style, [Larry] has another cool article on rolling your own robot arm cheaply with some foam board and hobby servos.