Automated Turntable Photography

April 11, 2012 by Mike Szczys 3 Comments

[Muris] has a friend who is selling items on the internet. This friend wanted a simple way to make rotating images of the products and asked him to help. The result of his labors is this base unit that drives the turn table and controls the camera.

The first iteration of the turntable was powered by the stepper motor from a floppy drive. A disc was mounted directly on the motor spindle, but the results were a bit poor. This is because the motor had a fairly low resolution of 200 steps per rotation. That doesn’t allow for smooth animation, and there was a lot of vibration in the system. An upgrade to the geared system you see above included swapping out that motor for one from an old scanner. Now it achieves 1200 steps per rotation and the vibration is gone.

The connectors seen in the base are USB, incoming power, and shutter control. [Muris] wrote a program to control the PIC 16F628A inside the base. The program sends commands via USB and has parameters for number of frames per rotation, direction of rotation, and the like. Set it up as desired, place the product on the turntable, and hit start. Unfortunately there’s no video of this in action because [Muris] gave it to his friend as soon as it was finished. We guess the fact that he didn’t get it back means it’s working great.

If you don’t mind some rough edges and exposed wiring you can throw a system of your own together pretty quickly.

Wind-powered POV Weather Station

March 2, 2012 by Mike Szczys 23 Comments

The more we think about this one the more we like it. [Michael] built himself a wind-powered persistence-of-vision weather station. Okay, that sounds interesting, but he ups the ante when you find out what’s included in the system.

A stepper motor acts as the generator which powers the electronics. As we’ve seen before; if you spin the shaft of a stepper motor electricity is produced. [Michael] is actually spinning the housing of the motor, with the shaft mounted to the base that holds the weather station in place. This way, the electrical contacts are spinning along with the blades of the generator. By mounting all of the electronics on these blades he gets around the problem of transferring power onto a spinning platform.

A set of LEDs on the end of the blades display temperature and relative humidity readings. A hall effect sensor pulled form an old floppy drive syncs the display with the rotational speed. He’s even got a shunt system which keeps the input voltage at a safe level, and will act as a break in high winds to keep the rotors from spinning out of control. See what we mean? An interesting idea because a fantastic project when you build in features like these!

Investigating The Generative Properties Of A Stepper Motor

January 23, 2012 by Mike Szczys 40 Comments

You probably know that if you spin a motor (mechanically) it generates electricity on what would normally be the inputs. This can be a problem when you shut off a spinning motor and is the reason that protection diodes are built into motor driver circuits. But [Dino] isn’t interested in driving a motor, he wanted to see what he could do with the electricity generated by spinning a stepper motor.

He built the test rig that you see above for this purpose. In the foreground a 12V DC motor is held in place with an electrical conduit clamp. This connects to the stepper motor being tested using a segment of rubber tube. The DC motor provides a reliable input for his experiments, but could be replaced in the future by a propeller to make it wind powered, or by a water wheel. Check out the video after the break to see what kind of juice [Dino] gets out of it, and how it can be used for powering LEDs, recharging batteries, or driving a motor.

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High Speed Stepper Driving: 25k Steps Per Second

December 14, 2011 by Mike Szczys 30 Comments

Stepper motors are pretty easy to control with a microcontroller. But if you’re looking to run then at a high number of revolutions per second things get tricky pretty quickly. [Uwe’s] been learning about and building stepper drivers for years, and recently he decided to build a high-performance driver based on a MicroChip reference design.

As with the reference design, his board uses a dsPIC33. But instead of using a series of discrete MOSFETS to switch the signals to the motor, he sourced an L298N motor driver. That’s it sticking up next to the large capacitor. When driven hard it needs its own heat sink, which [Uwe] cut from a larger CPU heat sink. During development, he decided to use interrupt-based PWM rather than the hardware PWM offered by the dsPIC. It works, but he would go the other route if doing it again.

For the pedestrian, the video after the break has all the details you need. For those that really want to dive in, [Uwe’s] multi-paged write-up is worth bookmarking.

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Arduino Boards Control Cheap Clockworks Via Coil Injection

September 27, 2011 by Mike Szczys 23 Comments

Here’s a couple of clocks that use Arduino boards to control inexpensive clockworks. The concept is quite simple, and perhaps best outlined by [Matt Mets’] article on the subject. As it turns out, these clockworks are driven by a coil, forming a device that is quite similar to a stepper motor. If you solder a wire onto each end of the electromagnetic coil and hook those to a microcontroller, you can alter the speed at which the clock ticks. Just drive one pin high and the other low, then reverse the polarity for the next tick.

The clock you see on the right (translated) is a store-bought cheapy. The Arduino barely visible at the bottom of the image is sending pulses once every second. But as you can see in the video after the break, holding down a button will fast-forward through time. [Sodanam] posted his code as well as pictures of the hardware hack itself.

To the left is a horse of a different color. It’s a clock modeled after the Weasley household clock from the Harry Potter books. The clockwork trick is the same, but the Arduino uses GPS data and NOAA weather information to set the status.

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Sustainability Hack: Wind Turbine Battery Charger

September 27, 2011 by Mike Szczys 16 Comments

Hit your parts bin and set aside an afternoon to build a wind turbine that recharges batteries. You can see two AA batteries hanging off the side of this small generator. You only need a few parts to make this happen, and chances are you have them sitting in your junk bin already.

The generator itself is a small stepper motor which can be pulled from a floppy disk drive or a scanner. The blade is cut from a single piece of 3.5″ (90mm) PVC pipe, with another piece of smaller-diameter pipe serving as the body of the turbine. The tail-fin makes sure it’s always pointing into the wind and was made from some plywood. As the blade spins, a current is induced on the control pins of the stepper motor. By building a pair of bridge rectifiers and using an RC filter you’ll get the most out of the generated current.

This turbine can charge a pair of NiCad batteries in about 10 hours, but it might be worth developing some smart circuitry to manage charging. If it were able to choose between a dedicated storage battery and the on-board battery holder you could put all of the wind energy to good use.

[Thanks Michael]

Building A Stepper Driver

July 11, 2011 by Mike Szczys 8 Comments

[TBJ] is building what he calls a junkbox 3D printer. You can probably guess that he’s trying to salvage most of the parts for the device, and after pulling a stepper motor from an old printer he was in need of a way to control it. What he came up with is a stepper driver that uses discrete components that are easy to acquire and inexpensive. The design calls for two inputs, one that toggles the direction in which the motor will spin, and the other that triggers one step of the motor. A CD4013 dual flip-flop takes care of both of these inputs in one chip package.

The motor is driven by a pair of H-bridges that he built using six transistors each. The trick with a stepper motor is that you need to drive the four poles of the motor to a specific logic level at a specific time. For this [TBJ] uses a CD4017 decade counter. A network of diodes grounds half of the output lines based on the flip-flop that controls direction. Our friend the 555 timer provides a clock for the circuit, keeping everything moving at a predefined rate. Check out the video after the break for an explanation and demonstration.

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