Tag Archives: stepper motor

“Dimmer Not Dumber IV” – the fader continues

The “Dimmer Not Dumber” fader saga has not closed. In the spirit of invention being the mother of invention, introducing “Dimmer Not Dumber IV“, for a customer who wants to control slide dimmers.

Here the “Dimmer Not Dumber IV” is going through its “homing” sequence. The stutter near the top allows the dimmer to travel beyond the proximity detection to reach maximum brightness.   Once homed, the dimmers drop to the OFF “rest” state. The dimmers are programmed to move through a specific light sequence when triggered by the external control signals.

Dimmer Not Dumber IV: with pair of electrical light slide dimmers and control unit

Where the original Dimmer Not Dumber II” design used servo-motor to control a residential rotary dimmer, the new design (and its failed predecessor, “Dimmer Not Dumber III“) uses a stepper motor to control a slide dimmer.

Talk about a hammer to crack a nut. This design uses a NEMA17 stepper coupled to a 1/4” 20 screw upon which a slide assembly that captures a corresponding nut rides. The end-stop, necessary to establish a “home” position for the steppers, uses an inductive proximity detector that is activated by the presence of a machine screw embedded in the slide assembly.

Dimmer No Dumber IV: showing fader base, motor mount, proximity mount, and slide assembly.

The pieces are cut from 12mmm and 6mm HDPE and connected using M3 machine screws. The whole assembly screws to the slide dimmer using the normal fascia mount.

Dimmer No Dumber IV: closeup of the 2-part slider assembly that captures the nut that rides on the screw. The countersink-head machine screw on the left triggers the inductive proximity detector at a distance of ~ 5mm.

The control software consists of an Arduino Nano and a pair of DRV8825 stepper motor drivers. The electronics, steppers and proximity detectors are powered through a 12v connection, and 24v control signals are conditioned to lower voltages for the Nano. Screw terminals are used to make the electrical connections for power, control signals (reset and trigger) and each detector.  The entire electronics assembly is housed in a small enclosure created with from a 12mm HDPE base and 6mm HDPE top plate.

Neater, huh!

 

 

seXY – computer-controlled mechanism for a new clock

s e X Y

Computer-controlled mechanism for a new clock

seXY is a motorized mechanism that under computer control can move a carriage slide in two separate axes: up to 380mm (15″) in the X-axis (side to side) and 350mm (13.5″) in the Y-axis (front to back). A huge “design space” to play with! My intention is to mount a head to the slider equipped with a servo that engages either a pen or an eraser… More to come on that front!

In the following video, the left and right steppers are being controlled by the micro-controller which is just moving the slide to and fro the X and Y axis, and the four diagonals.

seXY: Stepper-driven X-Y mechanism

So, this weekend CNC project was largely inspired by an interesting product called AxiDraw,  that is described as “the personal writing and drawing machine that mixes the precision of robotics with the warmth of a hand-drawn note.”  I was primarily fascinated by the control belt arrangement that allowed the two steppers to be stationary. This avoids all the complications of creating wiring harnesses that have to flex with the machine movements.

It appeared from the video and other similar designs that the two steppers are fixed at either end of the x-axis and that axis movement is achieved by moving BOTH. This belt arrangement has an interesting effect. When both steppers turn in the same direction, the carriage slide moves along the x-axis. When the steppers move in opposite directions, the carriage slide moves along the y-axis. If either stepper is stopped, the carriage slide moves along a diagonal.

Neat, huh.

So I decided to design and build one.

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Sands Of Time

Introducing my latest work-in-progress: The Sands of Time

This is a project inspired by a piece of articulated artwork by Bruce Shapiro, called “Sisyphus Machine“, described as… “an elaborate kinetic drawing machine that uses magnets to drag rolling steel marbles through a thin layer of sand to create complicated mandala-like patterns”. I found the the patterns to be mesmerizing. I felt I could create something along the same lines to experiment with dynamically changing patterns, and – in keeping with my clock making and fascination with time- that would allow the ephemeral praxis of writing time in the sand….

UPDATE: 9 June 2016: My first sand pattern with “Sands of Time

The software traces a simple helical pattern that traverses the centre of the drawing surface so the final design shows two spirals… Neat huh!

Sands Of Time

Sands Of Time: my first sand drawing.. Here, the ball is making a pair of intersecting spirals.

A new top lip – made of 6 identical sections of alder that I shaped on my CNC machine – captures an acrylic drawing surface that is covered in a thin layer of finely ground sand. The magnetic coupling between the carriage’s magnets and the 12mm steel ball bearing is lower than expected so that the friction of the sand is sometimes too great and the ball loses connection. The gap that separates the magnet from the ball is slightly over 3/8″ – 1/4″ ply (as the top support) and 1/8″ acrylic – and this appears too great to ensure a really strong magnetic coupling. So, rather than redesigning the top to reduce this thickness, I shall try out a spherical rare-earth magnet, rather than the current steel ball bearing.

Here, a small thrust bearing is magnetically coupled to the carriage of the carousel, which is rotating underneath a temporary sheet of acrylic. In the completed design, a thin layer of fine sand will sit atop the acrylic and a ball bearing will be moved through it. Articulation of the carriage and carousel will allow for the tracing of “mandala-like” patterns.

In this clip, the carriage and carousel can be seen operating together under the control of separate stepper motors. The unique design (all mine!) places the carriage servo at the absolute centre of the carousel’s rotation. This geometry allows completely independent motion of the carriage and carousel. In other words, the carousel can rotate freely in any direction while the carriage can traverse the carousel’s diameter, and both can operate completely independently.

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Time Weights 4 !Man clock

My latest project is the “Time Weights” Clock.

As it sounds, the time is presented as the height of three moving weights representing the current time hours, minutes and seconds. The twist is that each of the weights are connected on one long continuous loop that is reeled in and spooled out on demand. The software determines the correct position of each of the weights based on the time and the geometry of the design, and turns each of the three stepper motors accordingly. It takes into account that each weight much also pass on the additional belt required by the more significant time element(s). Additional consideration is given to account for the difference in belt length around the stepper drive pulley and the weight pulley based on the vertical height of each weight.

An interesting mathematical problem to model and solve, indeed!

Time Weights

Time Weights: In progress. The three steppers driving the single continuous belt show hours, minutes and seconds. The spooling system, seen on the right, allows the excess belt to be spooled up while also allowing it to be played out as needed.

Here’s a (crappy) video showing the work in progress and the successfully operating spooling mechanism that was cobbled together from an old tape measure.

The video shows the spooling mechanism reeling in belt slack as the seconds weight crosses the minute boundary.

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LightWriter Clock: Resurrected?

The original idea for the LightWriter Clock was to play with the ephemeral nature of time – in that each specific measurement of its passing quickly fades into the past. In a very literal way, this clock writes out digits of the time onto a phosphorescent media which then slowly fade away.

Here’s the latest and long awaited update of the LightWriter Clock project, and yes, I did paint the body a lurid shade of lime! (Why, because I can! or at least had a can?)

The final design is covered with a sheet of clear acrylic, the bottom section of which is painted with several coats of a phosphorescent spray paint. Every 3 minutes, the LightWriter bursts into life articulating the two arms to write out, using a UV laser, the four digits of the time, in 24 hour format, onto the phosphorescent coating.

LightWriter Clock

LightWriter Clock

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ROUND ABOUT Clock

Continuing the theme of examining metaphors for the measurement of, and perception of, time, the ROUND ABOUT Clock makes concrete the response to “What time is it?” … which may be…  “it’s a round about eleven twenty five”.

Round About

Round About Clock: displaying 11:25 PM

A rotating face – the “round-about” – and a periphery of lights combine to replace the hands of a traditional analogue clock such that time is displayed both spatially and through continual movement. (I plan to design a new and larger top disc for the “round-about” to have the lights fully illuminate the numerals, but as a prototype, this is quite functional.)

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LightWriter Clock – reborn

The initial LightWriter Clock was designed to play with the notion of the ephemeral nature of time. The current time is “written” with light onto a phosphor-coated panel, such that the image of the time slowly fades away before the new time is written.

“Such are the metaphors we live with, Grasshopper!”

The original unit was designed and built almost a year ago yet has sat gathering dust for all that time (no pun intended). Now, with a new paint job (yes, really!) it is ready to be reborn.

LightWriter Clock

LightWriter Clock

Watch this space…
Video of the LightWriter Clock in action coming soon

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