Let's Make Robots!

Artist, first time robot creator

Hi everyone. I'm an art student who's doing my instillation for my Advanced Drawing class on automated art and the creative power of robots. Needless to say I'm quite lost when it comes to the mechanics of it. I got ideas, but ideas don't mean shit if they're not backed up by knowledge. That's why I'm asking you guys for help, and hopefully I can take the advice and use it to make some really effective pieces.


For the record, I don't have drawings of these (despite me having a vision of the final product in my head). I only just decided I'm going forward with the project, so descriptions will have to do.


In my mind, I'm picturing a roll of thick-weight paper going between two rollers, with a motor consistantly turning the rollers causing the paper to move, having it look like an asembly line. There will be colored ink or watercolors dripping onto the paper from above, which doesn't require any specific electronics. The "complicated" part would be a pen consistantly moving back and forth on one sie of the paper. In order to make the completed drawing interesting, I need some sort of way to introduce a randomness factor. I was considering having the pen speed up whenever the light level changed, or perhaps what would be even better is speeding up when a detector detects non-white on the paper in a specific location.


These are just ideas. And ideas are nothing if I can't put them into practice. I have some experience (in that I can solder and that my sister's boyfriend is fantastic at robots), I'm just curious if anyone can share resources to help me get started. I know basically nothing. I know to salvage motors from printers to use to spin the rollers, but I have no idea how to hook them up to a power source, and I know practically nothing about how to hook up a white-sensitive or light-sensitive detector to a motor that makes a pen go back and forth at varying speeds.


I'm not asking to have my hand held, I don't mind doing a little bit of reading and figuring it out for myself! But if anyone has any resources I'd greatly appreciate it. Thanks!





EDIT: Oh, I understand the issue of having a pen go over wet ink. At the moment that's not nearly as much of a concern as the electronic part of the machine/robot.

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Motors that are required to move forward and reverse are connected to a h-bridge. To move a motor in one direction with the ability to turn it off would only require a couple resistors, a diode, and a transistor or maybe a FET (Field Effect Transistor). If you want to control speed and direction though, you will still need some kind of h-bridge. What kind of h-bridge will depend on the motor/s you are using.

White sensing. IR detectors (Sharp IR detectors, or, homemade; search this site) 'might' have slightly different measurements due to wether they are looking at white or another color. CdS cells or LDRs (Light Dependent Resistor) are variable resistors that change resistance due to light. Light reflected off of white 'should' give a different resistance value vs. light reflected off of whatever color your ink/paint is.

I agree with Max. You might well be able to build what might be considered a BEAM painter (BEAM is a type of robot that is built without a microcontroller). You might even be able to control the randomness based on some kind of timer that 'counts' how long white has been 'seen'. A microcontroller would simplify things. If you are moving the motors all the time at a constant speed, maybe they don't need to connect to the microcontroller at all. A relay might work, one that is powered when the rest of the circuit is turned on. I believe, even in that case, you should keep all your grounds connected. Some of the smarter guys will set me straight if I am wrong. :)

My white sensing ideas may or may not work. A search for sensing color/white may be in your future. If you find that one of my suggestions work, I would offer that you might want to consider more than one sensor. Possibly in a similar setup to a line following robot. *Ding* Line followers typically use either LDRs or IR sensors. IR sensors have issues with certain types of light source. The sun is an extreme example. It throws out lots of visible light, but, it also does a fine job throwing out IR, which blinds many IR sensors. Fluorescent lights have been known to cause issues for IR sensors. You have been warned. :)

Just remembered you are moving the pen/brush/paint/ink back and forth. You will need an h-bridge to control the motor that moves your pigment dispersement. Preferably, you will also want a way to control the speed of that motor. Typically, we control the speed by putting a PWM signal on the Enable line of the h-bridge chip/circuit we use.

For extra randomness, high level languages that most microcontrollers are programmed in allow for a psuedo random number generation. I would suggest you look into ways to further randomize the random numbers you use. I would think a pair of random numbers coupled together by some form of math would accomplish that to an extent. There are others that will surely suggest better ways. :)

I believe I have managed to ramble my way through all of your questions. I have one question/request now. Please let us know what microcontroller you are considering, so we can offer more suggestions on where to find code snippets that might help you.

Using the duck-saying I mean that what you technically describe is a printer. Let's say an ink-printer.

Is it feasable for you to just use an old printer that gets its data from a computer? Like a regular print-job? Then there is no custom printer-mechanism and no micro-controller involved - just off-the-shelf material.

You might then stick a pen (or your watercolor ink pen) to the cartridge and there your "random" image appears.

So if you get more elaborate and maybe add a drawing-sketch with 

a) the installation you want to make to get a high-level-overview and
b) expected measurements (is it A4 you print or A0 or even bigger?) we could support you in the right direction.


Have a look at this video: http://v.youku.com/v_show/id_XMTM1OTAxNzYw.html

This is a robot I saw at the ShenZhen Hi-Tech Fair 2 years ago. The beauty of the robot is that it is just some servos and fishing line but it does exactly what you are talking about and paints Chinese charactors with a paint brush.

Perhaps you could experiment with a simple robot where the paper stays still and the robot runs about on the paper such as my Doodle Bot.

This robot was being controlled by a TV remote, video here: http://www.youtube.com/watch?v=jjDlVXBSvP0
The robot could also run autonomously, video here: http://www.youtube.com/watch?v=P7nDmojTbIo
These are all relatively simple robots that only need a basic controller, servos, geared motors and simple programming.

If you want to try something more creative then try spraying paint or coloured water like my SplatBot did when writting LMR in two colours on beach sand: http://www.youtube.com/watch?v=rXW559l9FwA

You could definitely do this using analog or TtL/CMOS circuitry, but I would definitely consider one of the many excellent micro controllers available to you. An Arduino, PicAxe or Basic Stamp would allow you flexibility and control over the project (for example, you could exchange the sensor that introduces the randomness for another type) but moreover, once you learn one of these systems and see what it can do, your world of artistic possibilities will explode! The start up costs aren't too bad, and considering the headache factor you eliminate, it makes good sense. Examine it at least. Welcome to LMR!

Welcome to LMR! best place for anything....well, robotics thing...

have fun! i've seen a lot of artists here as well, merging electronics with arts :)

Purchase a "Bread-Board", it would work best for your type of project, and it is solder free. Then you sould look into basic project boards and micro-controllers.  Your Idea will not need advanced programing so your scott free on that one.  All in all, just get your homework done, your plan will do great if you know what your getting into, because going in blind is never a good idea.