Is It A Stepper? Or Is It A Servo?

Almost everyone who is involved with 3D printing thinks to themselves at some point, “this could all be done using a closed-loop system and DC motors”. Or at least everyone we know. There’s even one commercial printer out there that uses servo control, but because of this it’s not compatible with the rest of the (stepper-motor driven) DIY ecosystem.

[LoboCNC] wanted to change this, and he’s in a unique position to do so, having previously built up a business selling PIC-based servo controllers. His “servololu” is essentially a microcontroller and DC motor driver, with an input for a quadrature encoder for feedback. The micro takes standard step/direction input like you would use to drive a stepper motor, and then servos the attached DC motor to the right position. It even signals when it has an error.
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Office Supplies Hexapod Tramples Your Excuses

We all have reasons why we’re not building cool robots. “I don’t have a lasercutter.” “I don’t have a 3D printer.” [JAC_101]’s hexapod robot dances all over your excuses with its tongue-depressor body and pencil-eraser feet!

Some folks like to agonize over designs, optimizing this and tweaking that on the blackboard. Other folks just build stuff and see what works. If you’re in the mood for some of the latter, check out some of the techniques at work here. Tongue depressors make a simple frame, and servos are lashed on with zip ties in place of fancy servo mounts (or hot glue). Photoresistors are soldered directly to their load resistors, making a simple light sensor. It’s all very accessible and brutally minimalistic, but it seems to walk. (Check out the video, below.)

Arduino code is available for you to play with, naturally.

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Adorable Matchbox Robot

[wattnotions] has been playing with matches, well the box they come in anyway. One day he was letting synapses fire unsupervised, and wondered if he could build a robot inside of a matchbox. His first prototype was a coin lithium battery and scrounged motors from those 3 US Dollar servos you can buy by the dozen. It scooted around just fine, but it drained the battery instantly and was a little boring.

Next, he etched a board. It had a little PIC micro, a connector for a mini LiPo, and an H bridge. It fired up just fine, and even though it drained the battery way too fast, at least it wasn’t brainless anymore. In our experience, robots tend to discard all the useful data they collect anyway, so being blind wasn’t too much of a problem.

Inspired and encouraged, with synapses gloriously undeterred, [wattnotions] set out to make a version 2. This time he ordered a board from OSHPark, made a 3D model in SketchUp, and proceeded to lock himself out from his own chip. Without a high voltage programmerhe was out of luck. The development was unfortunately put on hold.

It was fun to read along with [wattnotions] as he went on a small robot adventure. We hope he’ll complete a version 3 and have a swarm of the little fellows scooting around.

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Creepy Cat Eyes with a Microsoft Kinect


Ever feel like someone is watching you? Like, somewhere in the back of your mind, you can feel the peering eyes of something glancing at you? Tapping into that paranoia, is this Computer Science graduate project that was created during a “Tangible Interactive Computing” class at the University of Maryland by two bright young students named [Josh] and [Richard], with the help of HCIL hackerspace.

Their Professor [Dr. Jon Froehlich] wanted the students to ‘seamlessly couple the dual worlds of bits and atoms’ and create something that would ‘explore the materiality of interactive computing.’ And this relatively simple idea does just that, guaranteeing some good reactions. 

As you’ve probably gathered from the title, this project uses a Microsoft Kinect to track the movement of nearby people. The output is then translated into actionable controls of the mounted eyeballs producing a creepy vibe radiating out from the feline, robot poster.

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Attiny PWM Generator and Servo Tester


Having the right tool for the job makes all the difference, especially for the types of projects we feature here at Hackaday. [Jan_Henrik’s] must agree with this sentiment, one of his latest projects involves building a tool to generate a PWM signal and test servos using an Attiny25/45/85.

Tools come in all kinds of different shapes and sizes. Even if it might not be as widely used as [Jan_Henrik’s] earlier work that combines an oscilloscope and signal generator, having a tool that you can rely upon to test servos and generate a PWM can be very useful. This well written Instructable provides all the details you need to build your own, including the schematic and the necessary code (available on GitHub). The final PWM generator looks great. For simple projects, sometimes a protoboard is all you need. It would be very cool to see a custom PCB made for this project in the future.

What tools have you build recently? Indeed, there is a tool for every problem. Think outside the (tool) box and let us know what you have made!

The inner workings of servo motors

Servos seem to be the go-to option when adding motors to hobby projects. They’re easy to hack for continuous rotation for use in a robot, but with the control board intact they are fairly accurate for position-based applications. But do you know how the hardware actually works? [Rue Mohr] recently published an article that looks at the inner world of the servo motor.

As you know, these motors use a voltage, ground, and signal connection for control. The position of the horn (the wheel seen on the servos above) is dependent on that control signal. The duty cycle of a 20 ms pulse decides this. Inside the housing is a control board capable of measuring this signal. It’s got a chip that monitors the incoming PWM pulses, but that’s only half of the equation. That controller also needs feedback from the horn to know if its position is correct or needs to be changed. Integrated with the gear box that connects the motor to the horn is a potentiometer. It’s resistance changes as the horn turns. Knowing this, it is possible to fine tune a servo by altering that resistance measurement.

Crafting a hexapod with an RC controller

Here’s a fantastic project that lets to drive a hexapod around the room using an RC controller. [YT2095] built the bot after replacing the servo motors on his robot arm during an upgrade. The three cheapies he had left over were just begging for a new project, and he says he got the first proof-of-concept module put together in about an hour. Of course what you see above has gone through much improvement since then.

The three motors are epoxied together, with the one in the middle mounted perpendicular to the motors on either side of it. Those two are responsible for the front and rear leg on each side, with the third motor actuating the two middle legs. It’s a design we’re already familiar with having seen the smaller Pololu version. You might want to check that one out as there’s some slow motion video that shows how this works.

[YT2095] added control circuitry that includes an RF receiver. This lets him drive the little bot around using a transmitter with four momentary push switches on it. We love the idea of using copper clad for the foot pads.