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.
Brushless motors and the way in which they are controlled can be a bit of an enigma to those just starting out in hobby electronics. [Andrew] from spingarage thought it would be helpful to put together a quick tutorial showing how he built a simple brushless motor controller in about a day’s time. He constructs everything on protoboard from components he acquired at RadioShack in order to demonstrate the ease of sourcing parts and building a brushless motor driver.
While he skips most of the theory behind brushless motor control itself, he does touch on the signaling these motors require for movement as well as how motor position is determined. Specifically, he expands on how half-bridges can be used to create the sine wave signaling required by a single motor input, as well as how three of these can be combined to drive a brushless motor.
The post is the first in a series of posts about brushless motors, so we should see some code examples and some practical applications in the near future.
[Nothinglabs] built this motor controller as an alternative to using an H-bridge. They call it the RAT controller which stands for “Relay and Transistors”. You can see above that two Darlington transistors along with their base transistors allow logic signals to switch the relay on and off, driving the motor in one direction or the other based on the open or closed state of the relay. See it working in the video after the break.
It’s a nice little workaround with few parts, but because the relay is mechanical there will be a short lifespan when compared to solid-state motor controllers. That’s okay, because the motivation here was lack of parts on hand, rather than an increase in performance. It’s also worth mentioning that all of these parts can be purchased at your local Radio Shack when you don’t want to wait for component orders by mail. We certainly appreciate that it takes far few components than [David Cook's] H-bridges. His designs are our favorite - we’ve used them in our own projects - but for quick and dirty you can’t beat five components and the short assembly time needed when using this type of dead-bug style soldering.
The parts laid bare in the picture above all make up a roll away alarm clock that flees when you don’t get out of bed. It’s an interesting idea, but considering most folks don’t sleep on hardwood floors we can understand why [TheRafMan] was able to pick this gem up for under $5. That’s quite a deal because there’s a very usable LCD module at the top. But for this hack, he focused on using the gearhead motors to make a programmable rover.
In order to make this programmable [TheRafMan] had to add a microcontroller. He chose an Arduino variant, called the Ardweeny. It’s a board that piggy-backs the ATmega328. But he didn’t use a stock Ardweeny; he’s altered it to play nicely with jumper wire. The uC is able to interface with the gearhead motors thanks to an L293D h-bridge motor driver chip. As you can see in the clip after the jump, the rover can now be driven around using a Wii Nunchuck or via a USB connection. If you’ve got a Bluetooth module lying around it wouldn’t be hard to make this a wireless solution that can be controlled with the accelerometers in a Wii remote.
His first entry is a low-power H-bridge, which can be used to drive small servos. While he admits that it is a bit odd to build use a 555 timer to construct an H-bridge, they are cheap and plentiful enough to justify their use. Check out the video below to see the simple H-bridge controlling a servo.
[Bob's] second entry is quite a bit more complex than his H-bridge. His secret knock detector listens for a pattern of knocks, triggering a relay if the proper cadence is detected. If a knock is heard, the first 555 timer starts, listening for another knock within a specific time range. If a knock is heard during this period, the next timer is triggered, and the process is repeated. Subsequent knocks must be timed correctly, or the circuit halts, waiting for a reset timer to expire before listening is resumed. It’s a bit hard to get the knocks just right, but that should be fixable with a few small tweaks.
The third entry he sent us is a project that is pretty common, though with a somewhat uncommon implementation. Class D amplifiers are often built as low-power headphone amps for personal audio applications. He liked the idea of a Class D amplifier, but wanted to build something with enough power to listen to his music in a small room. To accomplish this task, he looked over the internal block schematics of a 555 timer and constructed a pair of high-power 555 timers himself, using discrete components to mimic those usually found in the 555 package. His results were decent, though admittedly not of the highest quality, and could be tweaked a bit to provide better sound fidelity.
Continue reading to see videos of each project in action.
This collection of model vehicle hacks adds obstacle avoidance in an attempt to make them autonomous. At the front end you’ll find two PCBs which use IR approximation to monitor the road ahead. We’re not familiar with this particular use of these IR receivers (TSOP1738) which we’re used to seeing in remote control receiver applications but if recent posts are any indication we think you’ll enjoy the use of a 555 timer on each of those boards.
The rest of the hardware is pretty common, a PIC 16F628 does the thinking while an L293D h-bridge drives the motors. Alas, we didn’t find a video, or even a description of the finished project. But there are full schematics, board layout pictures, and the code for both this vehicle and a second Tank version.
I find that I do a lot of fun projects but I’m very bad about documenting them when I’m done. Holidays are for hacking (in my mind) so I usually plan ahead and do something cool during my time off. This project, which I loving call the Autodine-2009, was a spontaneous event over Thanksgiving that I’m just getting around to writing about.
Our cat’s want to be fed at 6am and are very insistent about it. Like most folks, I’d rather be sleeping at that time of day so I built an automatic cat feeder. Now we sleep while the cats eat. We don’t want to rely on a hack to feed our cats when we’re away so I didn’t go the route of an Internet-enabled multiple-dose feeder. Instead, I used parts on hand to create a single-serving dispenser on a timer. A servo rotates a false bottom to gravity-feed the cat food. The servo doesn’t have control circuitry so it is controlled through an h-bridge (I did have to buy 2 transistors for that) by an AVR ATmega8 microcontroller. There are two salvaged tactile switches to set the time and timer, and a serial LCD display that I’ve had sitting around for years. Power comes from an old cell phone charger a friend had just given me that spawned the feeder idea when I asked myself “hmmm, what can I use this for”?
I’ll demonstrate this recycled device for you in a video after the break. This wasn’t as hardcore as my AVR Tetris build but I’m much happier now that I can sleep in a bit.