Monday, 20 May 2013

my Pi-Car

Pi-Car is a Raspberry Pi (RPi) controlled RC (remote control) car, for details click on the link. In brief Pi-car runs without pressing the remote buttons, instead we will send the instructions by a computer program. I have used the basic Pi-Car kit and Raster RC car Porche GT3 RS from Argos.

How it works?
We connect the RC circuit Left, Right, Forward, Backward button points and 0V points with RPi GPIO pins, using Pi-Car circuit which is made of 4 FETs and 4 Resistors. Need to write Python program that controls the behaviour of pressing the L/R/Frwd/Bkwrd button of the remote. For detailed instruction for building a car like this follow the instructions provided here

Here are the pictures of my setup

1. RC Circuit of Raster RC Car Porche GT3 RS from Argos

2. Make 5mm hole on back of the RC to create a passage for wires

3. Final setup looks like this

4. Here is a video showing how it works, doing one forward and backward loop, there is a sleep of 10 sec in between to change the position of the car

5. This video is showing car following the carpet perimeter forward and reverse

6. Sample Python script, here is link to my Python script, which is a modified version of the sample script provided by

Lessons Learnt
I think overall its a great project for any 10+ years old to learn computer programming in fun way. I found that even the five years olds were quite excited and amazed watching the car run by a computer instead of a remote, all they have to do is hit the enter key :-). They also got a hang of it, Big Computer talking to small one, Small one (RPi) is talking to remote and remote is talking to a car. :-)

Controlling a RC car is not that easy, as the basic car doesn't have speed control or break system. It simply runs based on how long a button is pressed, so getting a time accuracy is bit of tedious job and require lots of trial and error. Also it may not run the same distance on and off carpet due to variation in friction. The charge of the battery will also affect the distance it covers in a given time, for example with full charge it may cover 3 ft in 1 sec but with low charge it may be able to do only 2.5 or 2 feet. I think once you get hang of it its fun.

Sunday, 19 May 2013

Tinkercad got a new lease of life

Tinkercad is nice little tool for 3D modeling, specially designed for 3D printing. It's very easy to use compare to other free/open source tools like Blender, Sketchup, Audocad 123D etc. About a month back there was an announcement that Tinkercad will be discontinued as core team wants to pursue other goals. However interestingly on 18/05/2013 they announced that Audocad has agreed to lease a new life to this nice little tool.

I have mainly used two tools Sketchup and Tinkercad, sketchup is mainly used for Architectural design. The model coming out of sketchup is not ready for 3D printing, requires some special plug-ins to export the sketchup model to STL format. As such it may not be fair to compare Sketchup with Tinkercad, as both tool's are designed for different purpose but both are widely used by 3D printing hobbyist users.

What I like about Tinkercad (compare to Sketchup)?

  1. Import SVG, I like it as it makes it very to easy to convert a 2D drawing to 3D model. I have used it to make Map Jigsaw puzzle and Cookie Cutter.
  2. Some of my favourite features are Object rotation, push/pull, cutting, moving object from one place to other, joining two objects, making an object transparent etc.. are way to easy in Tinkercad compare to Sketchup
  3. Best thing in Tinkercad is,  object coming out is always a solid object unlike in Sketchup where sometimes you need to repair the STL.

I wish we have following features in Tinkercad, I am not an expert so if you think this is already possible in Tinkercad, feel free to post your comments.

  • Number of basic shapes available are bit limited, I wish we have Arc or round shape objects. As making round corners of the cube is not that easy
  • Drawing canvas size is bit limited and also zoom is limited
  • I miss the guide and measure tools of sketchup in Tinkercad, the scale tool in Tinkercad provides very limited functionality. I find it very difficult to measure the internal details of the object in Tinkercad. For example in this Map jigsaw, how do we measure the width and height of a particular state?
  • Adjust the size of the tool-bar icons and movement of tool bar side to top or bottom

My creations with Tinkercad
Micky mouse cookie cutter -
Gingerbread woman -
Samsung galacy Ace2 case -
India map jigsaw puzzle -
UK map jigsaw puzzle -

Note: Sketchup is not completely free but they provide free and licensed version both, the free version is quite good enough for any beginner. I find the plug-in architecture of Sketchup quite powerful, as it has allowed to build large list of free plug-in libraries by community.