The color mix master

A while back a friend asked me if I could build a custom toy for a little guy called Oscar. She said something in the lines of ”The little guy is crazy about knobs, button, switches and blinking lights. You know, the same stuff that you like.” Of course I could not pass up an opportunity to lead a new requite towards the world of electronics so I accepted. Now it’s finished and the Color mix master is born.


The basic function is that the six RGB diodes on the top is controlled by the knobs, switches and buttons below. The color mix master has 5 modes which can be cycled between by pushing the buttons at the bottom.

Mode 1

In mode one the three switches works as a way to input a binary number. The LED that correspond to the number set by the switches is lit up correspondingly. The three knobs that are colored red, green and blue can be used to set the hue of the LED.

Mode 2

In mode two the three switches works as a way to input a binary number just as in mode one. But what is different in mode two is that the all LEDs up to the number that correspond to the number set by the switches are lit up. The three knobs can be used to set the hue of the LED.

Mode 3

In mode three the switches works just like in mode two but LED color is a fading rainbow and the knobs have no function.

Mode 4

In mode four the switches works just like in mode two. The LED color is a some random sparkles in different colors and the knobs have no function.

Mode 5

In mode five the switches works just like in mode two. The LED color is a dot moving back and fourth between left and right with a fading rainbow trail and the knobs have no function.


The case of the color mix master is an old router that I have spray painted red. It had plenty of room inside after ripping out the old circuitry.

The LEDs are through hole APA106 LEDs and they function in all essence like the WS2812B that is sold by Adafruit under the name Neopixels. They have the nice ability that you can address each diode individually using only one output from the microcontroller. Each diode has a data in, data out, GND and 5V. The diodes are connected one after another where the output from one diode is the input for the next. To make the spacing between the LEDs match the holes I had drilled in the case I made a little jig with the same spacing between the holes as in the final case to use while soldering.

The microcontroller is an Pro Mini, it has the same Processor as the Arduino, ATmega328P, but it doesn’t have USB or a voltage regulator, this makes it bit cheaper but you have to take care of the usb communications and power control your self. To provide 5V power I used a standard LM7805 voltage regulator and a 9V battery. The LEDs shouldn’t be powered from the microcontroller directly because they consume quite a lot of power and you would risk damaging your microcontroller. Instead you can run power to the LEDs directly from the LM7805 as long as you remember to connect the ground to the same rail as the microcontroller is using. If you would like to build a similar device based on my code any microcontoller that can be programmed with the Arduino IDE can be used just as long as it has at least 6 Digital IO pins and 3 analog input pins.


The software is a real hack. It was done in haste to be ready for christmas and can be improved greatly. I had problems to get the debouncing library to work so every time I pressed the button it registered as two presses. There are also unused methods etc. but hey it works! The LEDs are controlled by the excellent library. The code is available at my github:

T-1000c, Killer robot chickens from the future

This easter the city has placed two giant chickens made from twigs outside my house as an innocent easter decoration. I however immediately recognized them for what they were; T-1000c:s, killer robot chickens sent back from the future! All I needed to complete the transformation was the telltale red glowing eyes.

I set out to complete the transformation. Since I did not expect to get what ever i built back again, I decided not to use any expensive components. I also wanted the eyes to turn off during the day to save battery.

What I came up with was a simple circuit, where a transistor acts as a switch and switches depending on the resistance of an LDR (Light dependent resistor). This way the eyes turn on at night when it´s dark outside, and off during the day.


  • 1 x 2n2222 Transistor
  • 1 x LDR that varies between ~6k ohm when exposed to light and ~60k ohm when it’s dark
  • 2 x red LEDs
  • 1 x 20k ohm resistor
  • 2 x 48 ohm resistor
  • Some perfboard and wires
  • 1 x 50 cm (20 in) stick
  • 2 x 1.5V alcaline batteries
  • Duckt tape

I taped together the two batteries with some aluminium foil, and placed them between the poles to make solid contact . I then waterproofed everything with duct tape and installed the whole thing by showing the stick through the head of the chicken.

So happy easter from jenslabs and the T1000c!


I have always wanted to use an accelerometer in a project, so when my daughter Beatrice was born I knew exactly what to build; The Hypno-Jellyfish! The Hypno-Jellyfish is a jellyfish-shaped toy filled with RGB LEDs that changes color when you move it. So if you have just become a father, (or want to give someone else a very personal/strange gift), this is the project for you.


Design requirements

When designing a toy for a baby you need to understand the intended users modus opperandi.

1. If it fits in the mouth, it will go in the mouth.

  • Has to be free of toxins
  • No small parts that can be swallowed
  • All parts that can be touched by the user has to be waterproof

2. If it can be pulled it will be pulled with as much force that can be achieved by a 0 year old.

  • Needs to be built to handle some serious pulling.

3. If it can be dropped on the floor it will be thrown on the floor repeatedly and you have to pick it up over and over again.

  • Make it undroppable or very sturdy.

4. Blinking lights are beautiful and will be stared at intently.


Step 1

To remove as much sensitive parts out of Beatrices reach as possible, I decided to go with a two part design. The first part contains the Arduino and the battery, this part will sit on top of the babygym and out of baby reach. The other part is the jellyfish, constructed from polymorph plastic, that contains the Neopixel ring and the accelerometer.

To achieve a sturdy connection between the two parts that would hold for design requirement 2, I made use of some paracord where I replaced the center strands wires from an ethernet cable. I could only fit two wires in each paracord mantle, so to get the 6 connections I needed, I had to use three pieces of paracord with two wires in each mantle. I then braided the paracords to make one wire. This way all mechanical stress will be picked up by the paracord and the wires will hopefully stay soldered in place.


Step 2 – Electronics

The accelerometer (MPU6050) is connected to the Arduino Nano with five wires.

  • MPU6050 – Arduino
  • VCC – 3.3V
  • GND – GND
  • SCL – A5
  • SDA – A4
  • INT – D2

The NeoPixel ring only needs VDD (PWR), GND and a DATA in. I chose to power the Neopixel ring from the 3.3V output on the Arduino. In a worst case scenario the Neopixel ring could draw to much power from the Arduino, but to save on the number of parts, and also number of wires, I decided to try it and it worked. Ideally I should have used a power regulator circuit to provide power to the Neopixel straight from the battery to avoid overloading the Arduino.

  • Neopixel Ring – Arduino
  • PWR – 3.3V
  • GND – GND
  • IN – 100 ohm resistor – D5

 Step 3 – Making the jellyfish

The jellyfish is made from Polymorph plastic which I bought of BLRTronics on ebay. Polymorph plastic is a really cool material. In room temperature it is hard and durable, but if you heat it to above 60 C it becomes translucent and soft, and can easily be molded by hand. It is non-toxic and is often used in medical implants. However it is not super easy to work with, and when it is soft it tends to stick to itself.

My first approach was to mold body and tentacles from one pice of plastic. As I was almost finished I decided to heat up only the tentacles to give them a final twist. This was a bad decision and all the tentacles got tangled and stuck to each other so I was back to square one again.

To avoid making the same misstake again, I decided to mold the tentacles and the bottom part of the body, (that houses the neopixel ring), as separate parts. I then heated the bottom part of the body and made little knobs with a pair of tweezers where I planned to attach the tentacles. Finally I attached the tentacles to the body by heating only the knobs on the body in some hot water and only the top of the tentacles to avoid a sticky tangly tentacle mess again.

This method turned out to be much more successful. After successfully attaching all tentacles, I attached the Neopixel ring and accelerometer to the bottom part of the body with a small pice of polymorph plastic across the ring and accelerometer. The top part of the body was molded around the paracord to avoid any joints to the body. To make sure all mechanical stress is picked up by the paracord, and not the wires, I made a big knot inside the jellyfish that is to big to pass through the hole. Finally I joined the top and bottom part of the jellyfish with another piece of polymorph plastic that I had heated thoroughly so that it was rely sticky and acted as a glue.

Step 4 – Code

The code is based on the i2cdevlib by Jeff Rowberg and Adafruits neopixel library. The basic concept is to read the position of the accelerometer every 300 ms and compare the result. If there is a big enough change between the current and last value it is considered as a ”movement detected” and the color changes. The code can be found at my github in the Hypno-Jellyfish repo.


If you don’t have any kids or know anyone who has and still want to build one, you can always claim you are going to use it for light painting.

Vacation project, a time laps panning rig from an egg timer and a bottle.

A positive thing with being on vacation is that you have more spare time than usual. A negative thing with being on vacation is that you are far away from your lab and tools. Luckily, creativity is not confined to any particular place and there is always something that you can use to build something. During one of my spare time moments, my eyes fell on an egg timer, and I remembered seeing someone using an egg timer to make a time lapse panning rig. This seemed like the perfect vacation project! Two plastic bottles, a board, a screw, a few minutes work and the time lapse rig was finished. tlr_final_sunset

How to build it


  • An Oval egg timer
  • A plastic bottle
  • A knife and a pair of scissors
  • A piece of string
  • A marker pen
  • An iPhone with the app iMotion or any other time lapse app.

Optional, for a make shift camera support.

  • Another bottle
  • A board
  • A screw


Step 1, fitting the bottle on the egg timer.

Use the string to find the circumference of the egg timer by wrapping it around the the egg timer and cutting it so the ends of the string meets. Now wrap the string around the neck of the bottle and mark the spot to cut, then cut the bottle’s neck at the mark. You might have to use the scissors to trim the size a bit to make it fit snuggly on top of the egg timer.

Step 2, cutout to fit the phone.

Cut the bottom of the bottle. Place your phone on its long side in the center of the bottle, then mark the thickness of the phone. Next, use your phone to mark its breadth to know how far to cut. Once you have made the marks, use the scissors to cut the bottle to the right shape.

Step 3, Setting up the shot

Launch the iMotion app and set the timer to take at least one picture every 2nd second. If you use less frequent shots the footage will be a bit choppy and not the fluid motion we want. On the 360 degrees shot at 1:09 in the video I set iMotion up to take one picture every third second and that turned out a little choppy. Wind up the egg timer and place the phone in the bottle, start the iMotion and wait.

Step 4, Optional, the camera support board.

I quickly realized that you often want to tilt the camera a bit, or that the wind knocked the camera over. To remedy this, I built a camera support. The camera support is just a piece of board with the bottom of a bottle screwed on to it. The bottle was cut to fit the bottom of the egg timer. This makes it more easy to place the rig on an uneven surface or to tilt it to take a shot at an angle.

A dirt cheap DIY digital microscope

When I first saw this instructable by Yoshinok on how to make a microscope using a lens from an old laser pointer, I knew that I had to build one. The first attempt turned out pretty well, but I did learn some things from the build.

If I was to build another one, I would make sure that I positioned the lens between the two threaded rods that holds the sample tray, rather than towards the edge of the plexiglass. The only structural support the sample tray has are the two wing-nuts that is used to adjust the focus with. This makes it sensitive to weight distribution and if the sample it self is heavy, then the sample tray will tilt outwards due to the skewed weight distribution. It´s  hard to find focus when the tray is tilted. This weight distribution problem could perhaps be improved with some washers on top of the wing nuts and in the original instructable Yoshinok uses washes on top of the wing nuts. I would also have made the plexiglas the phone is placed on slightly bigger to allow for different positions of the phone.

The second thing I found was that the nuts I used to hold the plexiglas the phone is placed on, are too thick. The laser lens has a very short focal length, so the sample has to be very close to the lens to get a clear focus. If the sample is small and flat, it will still be out of focus even if the sample support tray is raised as high as it goes before it is stopped by the nuts. I solved this by using a plastic lid that I had laying around, which fit between the supports to raise the sample of the sample tray so that it could be put into focus. I used M8 size rod and nuts but I would say that M6 would be enough and those nuts are much thinner.

It is a very fun and useful little thing and it is very simple both to build and to use.

The First fly


Coin and rollerball pentip

LCD Screens

Screen comparison between Sony Xperia ZR and iPhone 5. Max magnification of a white area.

Wild Strawberry

The second fly








The Circlon machine and the pen test.

After seeing a video by Robert Howsare, showing what he calleds ”a drawing apparatus” (built out of two turn tables and some wood), I was fascinated. The urge to find out what the design was capable of, was so great that I decided to build one for myself. Mine is built with two stepper motors instead of turn tables. Stepper motors are not as cool as turn tables, but they do give you the opportunity to control the speed and direction very precisely.

One thing that anyone who as ever built a drawing machine realizes, is that to get quality results you need a quality pen. There are millions of pens out there, but after a little trial and error I realized that rollerball pens or pens with gel ink are the best pen types for my machine. Both rollerball and gel ink pens use a water based ink that is less viscous then the oil based ink used in ballpoint pens. The Circlon machine sometimes move very fast, so the pen has to be able to release enough ink to make solid lines even at high speed. Rollerball and gel ink pens will release ink easier then the ballpoint, so they seem to be the best choice. To once and for all try to find the best pen for the Circlon machine, I bought seven pens from and did some testing.

The pens in the pen test are:

Pentel EnerGel

Pilot G-2 07_2

Pilot G-TEC-C 025 2

Pilot G-TEC-C4

Rotring Tikky Rollerpoint

uni-ball eye micro

uni-ball Vision Elite 2



The pens best suited for the drawing machine were the Pentel Energel Deluxe RTX and the Pilot G-2 07. These two pens were the only pens where the line was solid even at very high speeds. For normal hand writing I liked the uni-ball eye micro the best, however all the pens in the test (except the two pilot G-TEC-C models) were great for my style of had writing. Due to the very narrow tips of the G-TEC-C models, the pen has to be held at almost a right angle towards the paper to get good results, and that is not the way I like to write.

I have paid for all the pens used in the test my self and I have no affiliation with the

Pentel Energel Deluxe RTX

The Pentel Energel Deluxe RTX releases a lot of ink, and it does so very quickly. It was the best performer when it came to drawing a continuous line in the drawing machine, regardless of the speed. When left stationary in the drawing machine with the tip out, an ink blot formed around the tip. When it comes to handwriting, it might even be considered a bad ability that that the ink flows so easily. The lines are also a little to thick for my taste.

Pilot G-2 07

Before this pen test, the Pilot G-2 07 was my favorite pen. The one I had ran completely dry while demoing the Circlon machine at  Stockholm Mini Maker Faire. After the G-2 ran out, I switched to a Ballograf ballpoint pen and the results were quite disappointing with ink blotches and more mechanical ware on the paper compared to the gel ink Pilot G-2. The Pilot G-2 was the second best pen to use in the Circlon machine, it produced nice solid lines even at high speed. The only thing that made is slightly inferior to the Pentel Energel Deluxe RTX, was that the line thickness of the G-2 was not as consistent. After trying out all these pens, I now feel that the G-2 releases a little to much ink to be perfect in the machine.

Pilot G-TEC-C25

The Pilot G-TEC-C25 has the thinnest tip of all the pens in the test, and that becomes very evident when you try to write with it. It feels more like you are trying to engrave the paper than writing. You have to hold the tip almost perpendicular to the paper for it to release any ink at all, and that is not my style of writing. When it comes to the Circlon machine, I think it did slightly better then its thicker brother G-TEC-C4 but there are some gaps in the line with the C25 as well.

Pilot G-TEC-C4

While not as thin as the 0.13 mm tip of the C25, the Pilot G-TEC-C4s tip is still to fine for me to write with at a normal angle. This could be a good pen for drawing thin lines with a ruler, but it is not for writing. One use for it would be in the Circlon machine when running very dense patterns that tend to get messy with a thicker tip. However, the fine tip makes it very slow in releasing ink which makes it necessary to run at very slow speeds.

Rotring Tikky Rollerpoint

The Rotring Tikky Rollerpoint has a nice dark black ink which flows very easy. It’s a nice pen to write with but sometimes it feels like the ball at the tip gets a little stuck, this is a very minor thing but I did notice it. At slower speeds I think that this pen could work very well with the Criclon machine, but at high speeds it does not release enough ink to draw a continuous line.

uni-ball eye micro

The uni-ball eye micro is the pen I liked best for writing with. It has a nice black ink and releases enough ink to make nice smooth lines, but not to much to cause ink blots. The tip runs very smoothly against the paper. It was not the best choice to use with the Circlon-machine, but it did ok there as well.

uni-ball Vision Elite

The uni-ball Vision Elite has an ink that is tinted slightly towards grey rather then black. It feels nice to write with, but I preferred the uni-ball eye micro. It did not perform as well as the uni-ball eye micro in the Circlon machine, and there is plenty of gaps in the line where the pen has been moving fast.

Eleven awesome robots!

In recent years, the number of robots and other kinds of self propelling machines has increased significantly. This new breed of machines resemble everything from humans, dogs and donkeys, to birds or insects. Perhaps I will have a robo butler in my lifetime after all!

Petman (Protection Ensemble Test Mannequin)

This anthropomorphic robot from Boston Dynamics is just as scary as it is impressive. Petmans intended application was to test out chemical protection suits.

Boston Dynamics is a spinoff company from Massachusetts Institute of Technology and was spun off in 1992. They are famous for having created a number of different robots between the size of a donkey to a small dog. Not much has been heard from the company since it was acquired by Google in December 2013. I can only go on to assume they are building something mind blowing.

Wild Cat

This dog sized robot from Boston Dynamics can move at a speed of about 16 mph on flat terrain using bounding and galloping gaits. It was developed using funds from DARPAS M3 program.

Magnetically Actuated Micro-Robots

This is a completely different piece of technology, but just as impressive. Imagine what you could do with control over swarm of ants at your fingertips. Developed by SRI with funds from DARPA, these antlike robots are controlled by magnetic fields. SRI calls this technique Diamagnetic Micro Manipulation (DM3). The intended application is that they should be used within the manufacturing industries with such tasks as surface mounting of electronic components.


This robot spider is more of a gadget then the high tech creations above but it is still pretty cool. Who wouldn’t like to have a robo-spider!


Developed by Harvard University, this robot looks more like an insect then a thing made by man. It uses piezoelectric actuators to propel the wings.  Piezoelectric actuators are strips of ceramic that expand and contract when an electric current is applied. Possible applications would be:

  • autonomously pollinating a field of crops
  • search and rescue (e.g., in the aftermath of a natural disaster)
  • hazardous environment exploration
  • military surveillance
  • high resolution weather and climate mapping
  • traffic monitoring


The Robot Dragonfly

The Robot Dragonfly from TechJect was successfully crowd funded via IndieGogo, the campaign ended December 31 2012. Judging from the updates on the IndeGoGo page, TechJect seem to struggle a lot with quality problems and has not yet delivered any products to their backers. If the Robot Dragonfly will be commercially available remains to be seen, but it is still one of the most beautiful flying robots I have seen.

KAIST Raptor

This biped robot from the MSC (Mechatronics, Systems and Control) Lab at the South Korean university KAIST is a fast one, it can run at an impressive speed of 45 km/h (28 mph). This speed is achieved with the help of active tail stabilization. The active tail stabilization also makes it able to run right over obstacles up to 100 mm high. Just imagine a pack of these hunting you, not a very compelling thought?

Out Runner

With its very original design and with speeds reaching 72 km/h (45 mph) on thread mill and 40 km/h (25 mph) when running out doors, it is a real speedster. The makers of Out Runner, Robotics Unlimited, are currently running a Kickstarter campaign, but with only a few days to go and 90k USD short of their goal of 150k USD, I don’t think they will go into production very soon.

Nano Quad Rotor Swarms

This video was shot at GRASP Lab, University of Pennsylvania. The first time I saw it, I was struck by the feeling that I was watching a swarm of insects behaving in a very unsettling way. Next came the feeling of wow! The quad rotors are developed by KMel robotics, consisting of Alex Kushleyev and Daniel Mellinger who, not surprisingly, are graduates of the University of Pennsylvania.


This robot from MITs  Biomimetic Robotics Lab was built to show the efficiency of a new type of motor.


Another robot from Boston Dynamics, this time it’s a cute little fellow called RHex. To me, it looks like he is WALL·Es lovable cousin from the country.

If you feel that there is a robot or a machine that I have missed make a comment with a link to it or send it via Facebook, Twitter or e-mail.

Teaching a laser cutter to draw

A few weeks ago I went to the mini maker faire in Stockholm and I wanted to show of the laser. Due to safety concerns I couldn’t run the laser out in public, but to be able to show of the CNC capabilities I built a penholder.

It is a quite simple build made out of wood, some plastic from an old cutting board, a few screws and a 9g servo. The servo is controlled by an Arduino, when the signal that would normally turn the laser diode on is high the servo is set to an angle that pushes the pen against the paper. The design was inspired by the brush holder on the WaterColorBot by Evil Mad Scientist. In their design the pen is lifted up by the servo rather then being pushed down like I did it. I don’t know what is best but it works both ways.

Stockholm Mini Maker Faire 2014

Here are some pictures from the Stockholm Mini Maker Faire 2014. I didn’t have much time to look around during opening hours so most of the pictures are taken before the faire opened on Sunday morning.

The most impressive build by far was done by Jonny Eriksson with his creation popmaskinen (The pop machine). Popmaskinen is an electromechanical one man band. Not suprisingly Jonny Ericsson was awarded maker of the year 2014.

Jonny is a musician/electrician/furniture carpenter and building Popmaskinen was a way for Jonny to put all his skills to the test. The heart of Popmaskinen is the spinning metal barrel called ”taktverket” which translates loosely into the pace keeper. The taktverk was designed by Jonny and then manufactured using a CNC-lathe. Taktverket contains a myriad of little holes into which little bolts can be inserted. As the taktverk spins the bolts that has been inserted into the taktverk hit little switches that in turn trigger one of the instruments to play a note. The function is similar to how a music box works. What note that gets played is controlled by the keys on the main unit and the strumming action is controlled by at what pace the the spinning cylinder is turning at.

To be able to play both in major and minor scales Jonny has built a custom two necked guitar where one of the necks is tuned to a minor chord and the other neck to a major chord. To control the guitars Jonny has mounted electromagnets all along the guitars necks and for the strumming actions. He had to rebuild the guitar three times before he finally got it just right. The casings that houses the mechanics of popmaskinen is built from MDF and the absolutely stunning finish of the surface has been achieved by using car enamel. The estethics of Popmaskinen makes me think of cars from the 1950s and the whole build screams hard work and quality.


Today I have been trying out StippleGen2 by Evil Mad Scientist. Stippling is when you create an image from little dots of the same color but with different sizes and with different density. StippleGen2 is built in Processing and uses an algorithm written by Adrian Secord. To try it out I used this classic picture of Louis Armstrong playing the trumpet. Once you load the picture you want to stipple the StippleGen2 starts crunching numbers and the algorithm continues to refine the result by applying the algorithm over and over again and the resulting image gets better and better.

After letting StippleGen2 crunch the numbers for a while I imported the resulting vector graphic file into inkscape and generated the G-code so that I could use my laser cutter to cut the image into a black paper. 2 hours and 23 minutes later I had a 20×20 cm piece of paper with about a 1000 holes in it and it looks awesome! Would be perfect for a lamp shade or just nice to put up in a window and let the sun shine through. I can highly recommend StippleGen2 it’s super easy and a lot of fun.