Tandem Bikes as Kinetic Sculpture

The Air Kraken is and extreme example of tricycle engineering, steam punk aesthetics and mobile sushi.  Gabriel Cain is building a custom tricycle that will transport two peddlers and a sculpture of a mythic sea monster: the Kraken!

Air Kraken tandem tricycle

Cain is building the whole bike from parts in his tiny urban garage and driveway.   Photos on Cain’s web site document the process of designing, building and eventually riding the tandem tricycle. His site includes links to resources for designs, plans and parts for building your own cycle.

4 wheel bicycle for two peddlers

Or you could buy a bike and customize it.  I have a four wheel tandem cycle that was manufactured for commercial use.  Currently my bike has hundreds of multicolored LED lights and I’m sketching plans to add more visual and sound art.  Cain’s project inspires me to get crackin on my plans and start making things happen!

I’ve been SCUBA diving for 14 years and I would love to make a whimsical sculpture of a sea creature using EL wire, LEDs and an aluminum wire frame.  I’m thinking tropical fish with graceful fins or a gentle jellyfish, or perhaps a school of little glowing fish.  Cain’s sea monster could chase my little fish around.  We shall see who has the faster fish!

How to make an art bike

A beautifully engineered bicycle is a work of kinetic art.  Taken to an extreme, a bicycle can be a platform for intricate sculpture, dramatic lighting and sound.  Issue 26 of Make magazine features a whole bunch of art bikes, go carts, scooters and skateboards.

Make: Live 06 – Bikes, Basics to Extremes
Wednesday April 13th, 9pm ET/6pm PT
Watch at makezine.com/live or on UStream

Why create an art bike?

My cycle is too wide to ride in a bike lane on an urban or suburban road, and way too wide to ride on the bike trails because the faster cyclists would not be able to pass safely.  Why bother making a huge bike that you can’t even ride on streets or trails?

Cain plans to ride the Air Kraken in the Fremont Solstice Parade and use it as his primary method of transportation at Burning Man.  My cycle was great at Burning Man last year!    As a work of art, the Air Kraken would likely be welcomed at festivals, parades and schools.  But mostly these creations are works of loveWe experience a fulfilling joy in the process of creation and in the sharing of our art with others.

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Sound Effects on a Bicycle

I’m sketching ideas for a sound system to attach to my two-person recumbent bicycle.  Clearly it needs great sounds to go with the amazing lights!  The lights are one long ribbon of RGB LEDs which slowly cycle through a rainbow of colors.  The photo below shows the bike on the playa at Burning Man 2010 just after sunset on Thursday night.  A 12V battery is stored safely in the Rubbermaid® bin behind the seats. 

My husband, Greg, on our 4 wheel bicycle for 2 peddlers

We plan to add a small microcontroller which will allow the lights to change in a wide variety of patterns depending on our mood.  Fast flashes, quick colors chasing, a pulsing red heartbeat, or moody fades of blues and greens. 

What kind of sounds?  Our first idea is animal sounds.  I want to find that old toy, the See ‘n Say, where you pull the string and “The cow says moo!”  The See ‘n Say is an amazingly durable toy based on the gramophone from the late 1800’s!  No batteries, just pull a string and a metal needle runs along the grooves in a plastic disk (like a record) to play the sounds on a diaphragm.  You can read more about how the See ‘n Say works at the How Stuff Works site. Unfortunately, the pull-string and gramophone technology was replaced by batteries and a microchip in the 1990’s.  I doubt that I can find a collectible 1980’s era See ‘n Say at Goodwill. 

My goal is to build the sound system out of cheap or recycled parts.  The microchips from recently discarded toys might be fun, or perhaps a new sound chip that I can program with sounds from the internet.  I don’t have a cow that I could record.

Atari Punk Console Kit for making weird sounds

In addition to animal sounds, I also want some Atari video game sounds.  For that, I’m buying a kit from Dorkbot Seattle as part of their annual Kit Night fundraiser.  Dorkbot Seattle  made a bulk order of kits from the MakerShed and are selling them at a slight markup.  I purchased the Atari Punk Console Kit  and my husband ordered the Lux Spectralis Kit .  We will solder the kits at Jigsaw Renaissance on Wednesday.  Then we will make videos of  annoying our cat with blinky lights and weird sounds on Thursday.  LOL

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Art: Mu the Robot

My friend and former coworker Mary R. Lee made an adorable robot gift for me.  I named her Mu (Greek letter μ) the Friendly Robot Muse.  In this photo she is standing in my home workshop next to my trusty Fluke multimeter.  Her warm smile encourages me to keep on making stuff and embracing DIY, craft and creativity.

Mu the Friendly Robot Muse

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Mousey Part 4: It’s Alive!

Mousey the Junkbot is alive!  I finished Mousey and let her zoom around the house on Friday, February 7, 2011 after a long session of soldering, gluing and Dremeling™.  She looks a lot like all the other computer mouse-based robots out there on the web.  This one is mine and she’s awesome!

Here are 3 ways to get step by step instructions on how to build Mousey:

My blog entries are intended to supplement the instructions written by Gareth Branwyn.  I have a list of tips for builders that I learned along the way.  See the previous 3 Mousey blog posts for tips and tricks for building an inexpensive robot.

Summary of this blog entry:

  1. Use the largest mouse case you can find so that components fit easily inside the small space.
  2. Position the motors so that they mostly stick out of the case and down at a 60 degree angle using hot glue to hold it in place.
  3. Use thin, 24 gage, stranded wire so that the folded up wires in the case don’t put unnecessary strain on the solder joints.
  4. Use an IC socket to hold your OpAmp integrated circuit chip.  The socket will take the heat of soldering and the pins will withstand the stress of the solder joints better than the fragile pins on the IC.
  5. Follow the bump switch instructions on the Instructables link, and don’t try my short cuts and don’t use super glue.

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You’re going to need all the room you can to fit all the parts and all the wires inside and still close the case.  Most of the problems I encountered had to do with figuring out the best way to fit all the parts and wires inside the case like a 3D puzzle.  Soldering inside that puzzle was also challenging.  The alternative is to have some parts mounted outside the mouse, which gives a different aesthetic.  I wanted it to look like a normal computer mouse rolling around the house.  If you want a road-warrior mouse with random cybernetic parts sticking out through holes in the case, then I say embrace that theme! 

2. Position the motors

Things got pretty crowded inside the mouse case as I was trying to fit all the parts inside so that the top and bottom of the mouse case would still close.  In order to fit the relay and the OpAmp IC chip into the front of the mouse, in front of the battery, I had to move the motors around four times.  I affixed the motors to the case with hot glue, so snapping the bond was fairly easy with a minimal amount of force using my hands and no tools.  I would put the motors in what I thought was a good spot, then many steps later as I would realize I had no room to glue down the parts, so I’d have to move the motors again!  In the final design, the motors were mostly sticking out of the case at about a 55 degree angle so that I had more room inside the case for all the electronic parts.  The exact degree isn’t important, as long as the two motors are symmetrical. 

After I was sure I’d found the best location for the motors, with just the smallest amount of the motor inside the case, I used lots of hot glue to really support the motor all the way around the bottom, left and right of the opening in the side of the mouse case. I used pliers to shape the hot glue.  After the glue dries, it is easy to pick the glue bits off of the metal pliers.

Tip for handling hot glue: 

You can reuse the same blob of glue when you reposition the motors by using the hot shaft of your soldering iron to reheat and reshape the glue that is stuck to your mouse case.  If you have a temperature dial for your soldering iron, set it to low.  I found that the soldering iron helped me shape the blob of glue into a wedge shape that would support the 60 degree angle that I wanted for my motors.  Safety: Ventilation is important for your health and use a wet rag to remove the excess glue from your soldering iron.  The glue fumes are not toxic, but they can still cause headaches and stink up the house.  I also blame the fumes for some of my less effective design decisions (keep reading). 

3. Tips for Wiring:

I used 24 gage stranded wire for everything except for the eye stalks.  The thin, bendy wire put less strain on the solder joints and allowed me to move stuff around while I was soldering in small spaces.  I used shrink tubing to cover many of the solder joints and prevent shorts.  I used electrical tape to cover some of the larger solder joints, fearing that I would need to re-solder them frequently in the final stages of development. 

In my photos, you can see that the wires inside the case are longer than they need to be.  I followed Gareth’s original instructions which suggested long 3” or 4” wires for many of the steps.  Now that I am done, and I can see exactly where all the components fit in my mouse, I could go back and shorten all the wires.  Shorter wires means easier to close the case.  The photos on the Instructrabls site show much shorter wires than in the original Make Magazine project. 

One of the comments from another builder on Instructabls shows that he used a prototyping board to make the circuits really compact and reliable.  Sure, it’s always possible to redesign and Build a Better Mousey!  At this moment, I’m not inspired to rewire anything.  I learned a lot about my tools, my abilities, and about junkbots from this project.  I am not fixated on perfecting this robotic toy. 

The one place where I used solid core 24 gage wire was on the eye stalks.  The red wires from the eye stalks get attached to the LED and the resistor.  These are nice thick connections.  However the black wires from the eye stalks get soldered to pins on the OpAmp Integrated Circuit (IC) chip.  These little IC pins are fragile.  When I closed the mouse case by squishing the top and bottom together, the force of the solid core wire pulled so hard on the solder joint to the IC pin, that it snapped a leg off!  Only a tiny bit of metal pin is still attached to the IC.  I blinded Mousey in one eye!  The poor thing just drove in circles. 

4. Use IC Sockets

 I had to completely replace my IC chip at a cost of $2.31, and find a way to put less strain on the pins from the stiff eye stalk wires. 

8-pin IC Socket

The solution is an 8-pin IC Socket for 95 cents!  The socket lets you solder your wires to the stronger pins of the socket, then plug your more expensive IC chip into the socket.  Your IC won’t have to experience the heat and stress of soldering!  Later, when you put this project on a shelf, you can pull the IC out of the socket for use in another project!  Win – Win – Win!  Now Mousey doesn’t just drive in circles.  She follows light and rams into furniture like she’s supposed to.

5. Making the bump switch (how not to use super glue)

The tiny switch that I salvaged from inside the mouse (which was the “clicker” button), has just a tiny red surface for clicking.  The design by Gareth Branwyn suggests using a piece of plastic, like a 2.5” x 0.5” piece of an old credit card and sticking it somehow to that switch.  There are two options here.  First, stick the plastic directly to that tiny red button.  The second is to affix the plastic to a front corner of your mouse case so that the plastic hovers in front of the clicker until it bumps into something.  I tried option 1 and it failed miserably.  I thought it would be a cool shortcut.  Wrong!  This poor decisions was made when I was tired and I wanted to finish before going to bed.

Read on to enjoy laughing at my failed “short cuts” for the front bumper.  I tried double sided sticky tape, but it wasn’t sticky enough to keep the plastic on after ramming into a wall.  The fast mousy hits with force!  The tape wasn’t sticky enough, so why not use something extremely sticky, like Super Glue!   Super Glue is very thin and can easily seep under the button which essentially glued the button in a permanently unclicked position.  I ruined that button.  Good thing my mouse had two buttons!  Another reason not to use a Mac mouse.  Finally I went to bed and later I moved the clicker button to be flush with the front of the mouse case and then attached the bumper according to Gareth’s instructions. 

Although I encourage mods, my attempt at modding the bumper failed.  Overall this project was a fantastic learning experience on a minimal budget.

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Art: Cross-stich Robot by Kristen Rupp

"And Far Away" by Kristen Rupp

I like this artist and this piece because she uses recycled materials (upholstery fabric) and a traditional craft (cross-stitch) to create endearing images with a very modern edge.  Art works by Kristen Rupp on display now in Seattle at Twilight Artist Collective.

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Mousey part 3: Troubleshooting a circuit

The problems I’m having with Mousey are not unique.  Checkout this YouTube video from Makemagazine with Bre Pettis, who had similar problems with the mouse driving in circles and a motor hooked up backwards.  Unfortunately, in his brief video he doesn’t go into detail about how he diagnosed and fixed the problems in the circuit.  He shows the Mousey not working, driving in circles like mine does, and then Mousey works properly.

This blog entry serves 2 purposes, it forces me to fully think through and write down my troubleshooting steps and test data.  Second it might help others who are troubleshooting similar circuits.  I know there are some kids and teachers who read my blog and hopefully everyone can learn that problems can be overcome with a series of hypothesis, tests and refined hypothesis.  The Scientific Method Rules!

Desired Behavior of Mousey: I want my 2 motors to receive the same power (voltage) when both light sensors receive the same ambient light.  If the right sensor receives more light, then I want the left motor to move faster than the right motor, thus moving Mousey toward the light.  Vice versa with the right motor and left sensor.  Also, when the bump switch is closed briefly (when bumped) it should reverse both motors, which makes the Mousey run backwards like it is afraid for a few seconds before returning to normal forward behavior.

Problem statement 1: Under ambient light, one motor consistently receives more power than the other, which would make my robot drive in circles to the left.  One motor gets about 4 VDC, the other gets 4.5 VDC.  Half a volt difference will make one motor significantly faster.  Note that I don’t have the motors attached right now because I’m isolating any differences in the two motors and focusing on the voltage that each one receives out of the Relay pins 4 and 13.  My relay is R72-11D1-5 and the PDF datasheet can be found on the NTE web site here.

Problem statement 2: The bump switch doesn’t cause the motors to reverse.  Let’s tackle problem 1 first and get to problem 2 in another blog post.

Mousey Circuit

Mousey Circuit, by Gareth Branwyn

Hypothesis 1: The light sensors are the problem, sending different readings when exposed to the same ambient light.

Test for Hypothesis 1: Check if the light sensors are sending widely different voltages into the Op Amp (LM 386).  Place the voltmeter between ground and the anode of each light sensor, noting that the anodes are connected to pins 2 and 3, respectively of the Op Amp (LM386).

Voltage across:
light sensor Left (touching anode and cathode of sensor pins): 2V
light sensor Right (touching anode and cathode of sensor pins): 2V
Op Amp pin 2 & GND: 0.0048 V
Op Amp pin 3 & GND: 0.0041 V
In other words, the left sensor is getting more light. 

Op Amp pin 5 and GND: 3.94 V
The output of pin 5 goes to the motors and divides the energy
between High (Relay pin 13) and Low (Relay pin 4 = GND = 0)

Transistor base and GND: 0.34 V (same across capacitor)
Transistor collector to emitter, and into pin 16 of Relay: 8.61 V
Relay pin 4 to GND: 0 V 
Relay pin 13 to GND: 8.61 V
Left motor  = Relay Pin  4 (0V)     to OpAmp Pin 5 (3.94V) = -3.94 V
Right Motor = Relay Pin 13 (8.61 V) to OpAmp Pin 5 (3.94V) =  4.67 V

Note that it’s perfectly fine that one motor gets negative and the other positive voltage  because the motors will be laying on their sides, and one rotates clockwise, the other counterclockwise to make the mouse go forward.

High voltage from the battery is around 8.6 V and I want the output of OpAmp Pin 5 to be exactly half = 4.3 V so that it equally divides the voltage between the two motors and makes them go the same speed, making Mousey drive straight.  I continued testing by metering OpAmp pin 5 and found that I could get 4.3 V when a lot more light goes into the right light sensor than the left, either by putting the left sensor in shade, or putting the flashlight right on top of the right sensor.

Troubleshooting the light sensors: Ideally the sensors behave the same way under the same light conditions.  If that were true, I would see the same behavior if I swapped the sensors on my board.  Specifically, I would pull the black wire from OpAmp pin 2 and swap it with the black wire from OpAmp pin 3.

Light Sensors

Original left sensor to Pin 2: 4.9 mV
Original Right sensor to Pin 3: 4.5 mV, a difference of 0.4 mV
Output of OpAmp pin 5 is 3.94 V (same as above experiment)

Swapped sensor to Pin 2: 5.4 mV
Swapped sensor to Pin 3:  4.1 mV, a difference of 1.3 mV
Output of the OpAmp pin 5 is worse at 3.69 V,
which makes Mousey spin in even tighter circles.

No sensor connected to Pin 2: 3.2 mV
No sensor connected to Pin 3:  2.0 mV
Output OpAmp Pin 5: 3.79 V

What have I learned from these readings?  OpAmp input Pin 2 always has a higher voltage than input Pin 3.  That doesn’t make sense to me.

Under similar light conditions we want OpAmp output Pin 5 to have an optimal midpoint value of 4.3 V.  What I learned from this test of swapping the sensors is that regardless of the sensors, the OpAmp seems to be receiving an input difference between pin 2 and pin 3, and outputting less than half of my Vmax.  I would prefer exactly half of Vmax.

Test 2 for Hypothesis 1:  Try different sensors

I purchased two IR LEDs (Infrared light emitting diodes) for ten cents each.  When I replaced my recycled sensors with these brand new ones, I still saw a difference between the input voltages, and still don’t get the desired 4.3 V output:

New IR LED sensor on OpAmp pin 2 = 8mV
New IR LED sensor on OpAmp pin 3 = 6mV
Output of OpAmp pin 5 = 3.6 V

Is this normal behavior for an OpAmp?  Time to research!

Hypothesis 2: Something is wrong with the Op Amp (LM386).
These chips are static sensitive and I could have fried it.  I do my work in slippers, on carpet, and a fuzzy cat frequently walks across my desk.  Static is everywhere!  A few quick tests showed that I did not fry it.

OpAmp LM386

The OpAmp LM386 datasheet is full of information that I don’t completely understand.  Pins 1 and 8 are the Gain pins, and the Mousey instructions in my book tells me that wiring them together helps make my circuit more sensitive to changes in the light.   So, on a whim, I removed the wire connecting pins 1 and 8 on the OpAmp and Abracadabra  I get the exact midpoint 4.3 V output from pin 5!   The midpoint voltage means that my motors will move at exactly the same speed.  The other thing I really want is for the output of pin 5 to CHANGE when there is a big difference between the amount of light on one sensor vs the other.  When I put one sensor in the shade and shine a flashlight on the other sensor, my pin 5 output barely changes.  It stays within 20 mV of 4.3 V.  I don’t want this behavior.  I want more dramatic changes in voltage to really make Mousey turn towards a light source.  From this experiment I learned that the gain really does make a more dramatic change in the output of pin 5.

What if I put a resistor instead of a wire between the gain pins?  I tried a  1000 Ohm resistor which acted a lot like the circuit did when it was wide open.  Then a 510 Ohm, and it still wasn’t sensitive enough.  Experiments with smaller resistors gave good results which I will describe below here.  When running experiments it is good to keep in mind our Desired Outcomes.  Remember a perfect midpoint voltage under ambient light is 4.3 V and a desired change in motor speeds will come from about 200mV of difference between the motors.

With the 200 Ohm resistor across the gain pins, I get close to my midpoint desired voltage.  OpAmp pin 5 = 4.2 V,  Left Motor = 4.2 V, Right Motor = 4.3V.  My light sensitivity test shows that when I put bright light on the Right sensor, the Right motor voltage drops to 4.2V and the Left motor speeds up to 4.36 Volts.  I like this combination of nearly equal speeds at ambient light (100 mV difference) and difference of 160 mV in the flashlight test.

With the 100 Ohm resistor across the gain, I now get an ambient light reading from pin 5 of 4.05V giving me 4.05 V on the left motor, 4.46 on the right, which means Mousey will veer to the left under ambient light.  Not optimal ambient light behavior.  Next I ran the flashlight test.  With light on the right sensor, the voltage of the right motor drops to 3.95 V   and the Left Motor speeds up to 4.2.  The delta in motor voltages is 250 mV in the flashlight test.  This circuit is more sensitive than the previous experiment, but the ambient light behavior is undesirable (400 mV difference).

Result:  Adding a 200 Ohm resistor across the gain of the OpAmp gives more accurate behavior in ambient light and flashlight conditions. Yeah!  To summarize what I learned today, I have a better understanding of the Gain on an OpAmp chip, and how to modify it using resistors to give a desired output.

Mousey Part 3: Add a resistor to the OpAmp Gain

Problem Behavior 2: Bump Switch behavior not working properly.

I pulled the DPDT (double pole double throw) relay off of my breadboard circuit and put it into another breadboard for “bench testing.”  A bench test is where you isolate one part of your circuit, in this case the DPDT relay integrated circuit.  A relay has a normal state, and a state when a voltage is applied across the coil, in this case pins 1 and 16.  It can be confusing reading the data sheet for your relay because each manufacturer might number their pins differently.  However all DPDT relays will have two pins for the coil, in our diagram 1 and 16.  Then two common pins, usually labeled COM1 and COM2, which are the outputs.  There are usually 4 inputs in a DPDT relay, two Normally Open inputs and two Normally Closed inputs, labeled NO1, NO2, NC1, NC2.

DPDT relay with numbered pins

When there is no voltage across the coil, then COM1 voltage = NC1 and COM2 = NC2.    When sufficient voltage is across the coil, then the internal circuit of the relay will switch so that COM1 voltage = NO1 and COM2 = NO2.  With this data, you can run a quick bench test using either a voltmeter or a couple of LEDs and resistors.

Another example of DPDT diagram from a data sheet

In my test, I discovered that my relay was broken because when I put 8 volts across the coil, the common pins still registered the values of the normally closed pins.  In other words, my relay would not switch.  So I threw it out and purchased a new one.  The new relay passed the bench test, so I put it back in the Mousey circuit and it worked fine!  Mousey now drives backwards when the bump switch is pushed, which puts voltage across the coil of the relay, which reverses the polarity of the voltage to the motors.  Make sense?  Please post questions in the comment section of this blog if you need help with your circuit.

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Mousey part 2: Reusing motors from old toys

Goodwill shopping spree

Bargain Electronics from Goodwill

Today I shopped for small DC motors to add to Mousey the photovore robot.  I love GoodWill. I donate often and shop carefully.  My Mousey robot needs 5V motors, so I searched specifically for RC toys that require 4 AA batteries = 6V maximum.   Then I manually spin the wheels to feel if the motors are resisting my motion a little bit.   When you manually spin the axle of a DC motor, you are essentially generating electricity, like inside a wind turbine.

Ultimately I purchased 2 RC vehicles, for $2.99 and $1.99.  I was excited to discover the $2.99 truck had 2 DC motors! Bargain!

I came home with a few extra cool thingies, in addition to 2 remote control (RC) toy trucks.   I also had to buy a 1970’s era analog clock made by General Electric for $1.99, a string of solar powered LED lights, a stick-on LED light (for mounting under counters), and a modem card with some useful chips and capacitors.


Harvesting Motors 

Goodwill had dozens of remote control toys without the control units.  Deconstructing the RC truck required two flat screwdrivers for prying plastic casing apart, two sizes of philips drivers for the small screws, and a pair of needle nose pliers for both prying and grabbing small plastic bits. 

$3 RC toy contains $3.50 worth of DC motors

The three dollar truck contained two DC motors which are similar if not identical to the “Standard Motor 3” DC motors from Solarbotics, which would be $3.50 plus shipping.  Note that Solarbotics is awesome and offers great pricing, but recycling old toys is more fun!  The toy also yielded a nice battery holder, wheels for a different project, and nice power cables on the motors.

RC toy front motor

DC motor in an RC toy

 I resisted using the dremel to cut the plastic toy, and instead opted to keep prying with the screwdrivers and pliers until the front motor was freed from the plastic chassis.  The ream motor is still in there, along with a nice hexoganal axle and probably some cool gears.  I’ll keep prying at that later.  For now, let’s put the motors on the Mousey test circuit!  IT WORKS!  Hop over to YouTube to see the video.

It Works! Recycled motors for Mousey!

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