Writing with solder

                                    So recently(the last few months) I have become obsessed with the idea of conductive inks and making circuits on fabric and paper, I think it is sheer brilliance to be able to design and build circuits as seamlessly as drawing on a piece of paper, now there are several products which achieve this , such as conductive thread , conductive ink and writing instruments etc (search for bare conductive on google).The thing is that by designing tools and technologies which enable us to do so will allow us to deal more with these circuits , we feel it as art, and because it is so much more simpler and fun we will do it more often not to mention the infinite creative possibilities which it will open up. Such a wonderful thought it is.

So being inspired and all I was looking at ways it can be done, here is what I tried.

•  First the simplest thing, you know pencil is made of graphite, and it is a good conductor of electricity, so I tried making marks of pencils on paper and measure the resistance. Obviously you need to make a very dark mark and greater the thickness greater is the conductivity. Typically with a mark of about 1cm long an 3 mm wide the resistance was about 400 k ohms and it was pretty much obeying ohms law( the longer the mark the greater the resistance)

•  Next it struck me that if I make two patches of pencil marks on the either side of the paper it will for a capacitor I tried it out but did get the chance to test it ( exams and all right now ), but it should have it in the order of picofarads .

•  Finally I decided to make an el cheapo version of a silver ink pen, to make it cheap, it does not have silver ink, instead as you write it leaves a solder wire on the paper( non melted), there are improvements to make like making the solder wire adhesive and making the tip a heating element do it can be fixed to any ic pin without any extra tools.
  
  
  
  So this is what i made till now i converted a normal pen to dispense solder wire, i made a spindle on the top with the refill and an aluminum pipe, it does not look pretty but it all i had at 4 am in the night, i will post an instructable on this soon
  
  
  
  This is how the solder path looks
  
  
  
  
  
  I know this is very trivial, but it is sort of nice, ill post more when i improve it
  Coming up resistor pen -set the value draw the resistor
  bye for now
  
  

Experiments with oobleck and homemade magnetorheological fluid

So i have tried to use the famous oobleck as a smart surface by making it harden under command by passing ultrasound waves through it, so what happened is well........NOTHING, turns out that you need a lot more acceleration to see any appreciable changes in its solidity.(tried out a small vibration motor as well, but as expected nothing happened).

Another failure is trying the same with a homemade magneto rheological fluid , but this time applying a magnetic field....still no appreciable results...but i think i will get a custom fluid form the metallurgy department and try more.Wish me luck.

The above picture is of the iron filings we collected from the construction site to make the magnetorheological fluids. we made acolloidal solution of this with vegetable oils.

Grid Follower (nexus IIT Bombay)

So as usual there is Nexus at this time of the year and looking at the problem statement i decided to ditch the event but...nancy was enthu about it so we all(me, mishel, nancy and chinmayee) decided to go for it with less than 2 weeks left for the event (more than enough anyway). By the way we won first place and kicked some a**.Check out the video here.

THE BOT:

I decided to get rid of the chassis and instead use the pcb itself as the base and attach the motors to it.

Specs:

THE MOTORS are rated at 12v and 420rpm they've become my favorite recently , been using them in most bots, they are small and give sufficient torque.(check out the pic).


We used standard 5mm IR DIODES AND EMITTERS , they have an angle of acceptance of 5 degrees, which is a good thing since they are directional the entire arrangement will be reliable because the emitters of one pair do not interfere with the other.


The sensing resistors are 10 k and each of the emitters are getting about 20 mA (which makes them pretty bright) .Refer to the circuit diagram at the end .

The micro-controller is an atmega 168 and we used a l293d for the motor driver

                                                                                                         This is how it looked after the assembly

We initially put two wheels in the front ,but later replaced them with a caster wheel (cause three wheels will always stay on the ground as all of them will be in one plane)

The sensor board is detachable and we put burg strips in front to protect the sensors

The green module you see on the top is a rf transceiver module based on the cc2500.(bought from robosoft systems)


I used a LM7805 as the voltage regulator to provide the 5v supply needed for the micro-controller.


This is the motherboard you ca see the slots for the micro-controller and the l293d in this pic

 Software:

We used arduino as the platform for this bot. the micro-controller has arduino firmware and is programmed in system using the rx,tx (usart) pins with connectors coming from the arduino decimilia board.

We used the flood-fill algorithm to find the shortest path to the destination,it optimizes the path and returns the path with the least distance and the least number of turns required.

You can checkout the code here.