Tag Archives: servo motor

PUSH-UPs… 2×8 pixel unit

After the design and build of the prototype PUSH-UPs articulated display panel, I have now built the first of 4 identical modules, each containing 16 controllable rods.

The four modules will form an 8×8 “pixel” animated surface display system to create a dynamically changing topography.

Stimulus for this display unit will be derived from a camera, an arrays of sensors, or purely from software that simulates different surface topologies.

PushUps: Top view of the 2×8 design

The design of the 2×8 unit parallels that of the 2×4 prototype. However, I changed the design of the servo horn and connecting linkage to ensure that the “pixels” fall onto a 33.34mm pitch (2 times the 16.67mm pitch of the LEDs on a 60 led/metre strip) for both rows and columns.

PushUps: side view showing the thinner servo horn and offset connecting linkage

In addition, the underside of the top plate was cut to allow for a simpler installation of the LED strip, that now contains a total of 34 LEDs.

PushUps: showing LED illumination for each “pixel” element

PushUps: all 16 units pictured in mid-articulation of a sine wave

PushUps: closeup of the servos

PushUps: closeup of the nano, 16-channel PWM/servo multiplexer and buck power supply

PushUps: close-up of the underside of the top plate showing installation of LED strip

 

Getting there!

PUSH-UPs: an articulated display panel

Introducing PUSH-UPs, an articulated display panel.

PushUps: a prototype for an articulated display surface

This is a 8 “pixel” prototype of a animated surface display system. The final goal is to create a surface with a hundred or more separately articulated “pixels” to create a dynamically changing topography. Stimulus for the larger unit may be from a camera, an arrays of sensors, or purely from software that simulated different surface topologies.

I’ve been talking about designing an articulated tabletop for sometime now – taking my inspiration from TRANSFORM, from the Tangible Media Group at MIT Media Labs. While I am not trying to copy their design, the key to this idea is in the design of a moving “pixel” that is small, provides several inches of “travel”, is able to be illuminated and, most importantly, cheap! This allows the design to be scaled to whatever size is desired. As this “pixel” element is actually a linear actuator, I have considered and experimented making all sorts of actuator designs but nothing I came up with is satisfying these criteria. In the video we can see that the table-top part of each pixel is a small square-section plastic tube connected to a wire or plastic linkage that connects to the control box below. But what is this control element and how does it provide the 4″ of travel that the video shows?

In a telephone discussion with Doug, an engineering colleague of mine, we noodled through some simple design ideas that would use cheap and readily available servo motors to articulate acrylic rods that can pass light.

So, the seeds of this prototype design were sown.

So, voila. PUSH-UPs.

I have made many designs using servos (see PopUp Clock, and Flipper) and I had plenty of the small metal-geared MG-90s on hand. In addition, I have created lots of clocks recently (yet to be posted) that use acrylic rods as light pipes for colourful displays so I had lots of 1/4″ and 3/8″ rod stock. And of course, I always have yards of addressable LEDs.

PushUps: going through the motions. Picture captured the unit articulating a sine wave

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Dimmer Not Dumber II: Servo-controlled light fader

Introducing the “Dimmer Not Dumber” II

A novel approach to fading line voltage lights!

This video shows me triggering the unit and then at the end, applying a reset signal. The unit is programmed to climb slowly to preset light levels upon repetitive triggering (10%, 20%, 30%, 40% and 100%). The reset signal applied at the end [44s] slowly fades down the light intensity to fully OFF.

A client wanted me to control the brightness of two sets of residential 110v pot lights. The only experience I have in controlling line-powered equipment is through using relays and opto-isolated solid state switches. However, these just provide simple ON/OFF control; and dimming lights is a whole different ball of wax! Plus, I did NOT want to mess with mains voltages!  There are devices on the market to do this but they are a) expensive, b) require electronics connected to the 110v load side and c) require real-time software to control (see discussion below). I wanted a simpler solution that used off-the-shelf residential electrical components, used simple electronics and gave me complete electrical isolation.

So, I came up with the “Dimmer Not Dumber” light fader design.

In this design, a servo motor is connected to the shaft of an unmodified residential light dimmer (Levitron, I believe) via a simple gear pair. This dimmer has a control shaft that rotates about 320 degrees to fade between full OFF to full ON. In addition, pushing the switch knob turns the whole unit ON and OFF.

As servo articulation is typically a maximum of 180 degrees, a 2:1 gear pair means that the full range of the servo translates into a complete rotation of the dimmer shaft. Control of the servo position therefore allows full control of the intensity of the light, so now all I have to do is connect the servo to a micro-controller and voila!  Full control of the light intensity and complete electrical isolation!

The Dimmer Not Dumber II version now includes an Arduino Nano, input conditioning for 5 – 24V triggers and a 5V buck converter. An 8-tooth gear attaches to the electrical fader’s control shaft and tightened with a small set screw, while the larger 16 tooth gear attaches to the servo using a plastic servo horn.  All electrical components are located within pockets in the base attachment plate while the upper plate holds the servo and has holes to access the pair of 3-pin servo connections and the 4-pin screw terminal block for external connections.

The body of the unit is made in two parts: a 12mm HDPE base attachment plate and a 6mm HDPE upper plate servo mount. The base and upper plates are attached using 3 3mm Allen-head bolts. The electrical fader mounts inside an electrical box as normal, and the Dimmer Not Dumber II unit bolts to the dimmer using the normal screw holes used for fascia plates.

Dimmer Not Dumber II: showing top face with the two servo pins and the external connection screw terminals.

Dimmer Not Dumber II: closeup of the two servo connector pins and the screw terminals for 9-12V, Ground, Trigger and Reset connections

“Dimmer Not Dumber” works like a charm, both in the light and the dark!

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CYCLOPS: servo-controlled Mechanical Iris

It’s been a while since I’ve posted – I have been busy though – and even longer since I posted something not related to a clock!

So, behold… CYCLOPS – The Mechanical Iris!

The video above – taken from the front – shows the completed CYCLOPS Mechanical Iris opening and closing as the servo runs back and forth. The video below – shot from the back – shows the mechanical linkages between the outer gear ring and the “petals” of the iris, and how the assembly operates to open and close the iris.

 

The CYCLOPS Mechanical Iris is made up of a face plate and five pivoting “petals”, each linked to a large rotary gear ring. The petals are carefully shaped to allow them to open and close a central iris that is 200mm (8.6″) in diameter. A 5:1 gear connects the outer ring to a small metal-gear servo motor mounted to the face plate. As the videos show, as the servo rotates through 180 degrees, the petals move so that the iris fully opens and closes.

Mechanical Iris: with outer gear ring and linkages to each of the 5 petals

Mechanical Iris: showing 5 petals in open position

Mechanical Iris: showing 5 petals in closed position

Designed and built as a proof of concept, the CYCLOPS Mechanical Iris was made quickly to test geometries and mechanical operation. It was designed using SketchUp with CAM operations using SketchUCam, and cut on my CNC machine  The face plate is cut from 12mm baltic birch, while the petals, linkages, outer ring, servo mount and servo gear are cut from 6mm HDPE (High Density PolyEthylene).

The initial design was for a proof-of-concept mechanical door to a “locked” compartment. Upon receipt of a trigger signal, the iris was required to open to allow access to the compartment behind and whatever it contains. While the POC was very successful, a number of design changes will be made to improve performance and usability. In this design, I incorporated three different linkage points on each petal, each a different distance from the pivot point, to test different lengths and designs of linkage arms. Tests showed that only the outermost (furthest) connection point was necessary, so the others will be removed. A simple curved linkage allowed for some spring in the mechanism that helped to fully close the iris, and this design element shall remain. The teeth of the outer gear ring covered an arc of 90 degrees. This proved to be in excess of what was needed and a sweep of only 45 degrees will be used. Additionally, the face plate will be redesigned with a deeper pocket to accommodate the outer gear ring and servo gear. This will also allow for a simpler servo mount and gear ring restraint. Also, the new face plate will also have simpler attachment points to the hidden compartment to make it easier to install.

Neat huh?

Pop-UP Clock… now in colour!

The Pop-Up Clock described in a recent post “Pop-Up Clock and Flipper Clock – Magnetic Digit Elements” is a work-in-progress proof of concept as I develop a full 4-digit clock (complete with flashing colon).

So far, the design displays the time on this single digit display in a sequential manner: two digits for the hour, then a dash (“-“) followed by two digits for the minutes.

Wishing to increase the illumination of the display and the contrast of the segments between ON and OFF (or IN and OUT) states, I made some changes. I added a strip of addressable WS2812 LEDs around the periphery of the display and blacked-out the rear of each segment so that little light passes into the HDPE when it is extended (OUT).  When retracted (IN), light from the LEDs shines into the elements and illuminates them.  In the software I reversed the direction of the segments so that when it is ON, it is retracted (IN).  Here’s a video that shows the effect.

This test shows considerable light bleed from the LED strip, and this shall be rectified when there is a fully enclosed baffle between the front plate and servo mount plate… In addition, I shall also increase the contrast of the segments with a better light seal.

As with many of my clocks, the accurate time is obtained from an NTP request to the US National Institute of Science and Technology (NIST) atomic clock server, using an ESP8266 WeMost D1 Mini WiFi module.  WiFi channel access parameters, local time relative to GMT, daylight savings active, and duration between display updates (minutes) are entered on its web server and subsequently stored in EEPROM when the unit is powered on for the first time, or if it fails to connect to the local WiFi channel.

Oh yes, and just for Lise, the display its blue!

 

Pop-Up Clock and Flipper Clock – Magnetic Digit Elements

Season’s Greetings


It’s been a while since my last post, while I have been working on two new proof-of-concepts for some new clock displays. Both of these displays employ magnetic coupling – attraction and repulsion – to animate elements (segments / flippers) of a numeric display that will be incorporated into a clock.

The first is a single 7-segment digit for a new POP-UP CLOCK.

Pop-UP Clock: Single 7-segment Digit

And the second, for The FLIPPING TIME CLOCK -is a 3×3 flipper array for a digit that displays numbers 0-9 as “pips” on a domino.

Flipper Clock Digit: Showing 3×3 array of flippers used to display the numbers 0-9 like pips on a domino

Interested in reading how these elements work????

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LightWriter Cricket

Hard on the heels of the LightWriter Clock project, comes my latest creation – LightWriter Cricket. This little critter writes the time with light onto a phosphorescent screen, and like the LightWriter, the displayed time just fades away until it is rewritten at the next minute. And, mirroring the ephemeral perception of time, each specific moment quickly fades into the past.

Here, LightWriter Cricket is seen writing out the time 14:13. Notice how quickly the display fades away such that the hours are almost totally invisible by the time the minutes are written.

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