Editing Arduino Laser Cannon

= Arduino Laser Cannon =

'''early draft, some text is mixed from another project, should be better updated in a few days'''

Before you get too excited:  the armament is just a laser pointer, so nothing blows up.  The arduino controls the aim of the laser.  Using a terminal program you can aim the laser in a number of directions.  Once aimed you can commit the position to memory and recall it later.


*Name:  Arduino Laser Cannon
*Status: in fairly early development, but is working. 
*Technology: Arduino 
*Author: [[russ_hensel]] ( where you can find an email address to reach me ) 
*Summary: An Arduino controls two servo motors to aim a laser pointer. A terminal program is used to control the Arduino. This project was written as part of a course on the Arduino at AS220 in Providence RI.  see: [http://as220.org/labs/pages/Arduino%20and%20Servo%20Motor%20Workshop#preview|Arduino and Servo Motor Workshop]

Archive for the project will be posted.  See download section below. 

This project can be used as is or may give you ideas for other similar projects: 
Example code for stepper motor control and for RS232 communications ( interrupt driven on the receive end ) on the PIC16F877A. 
Determining which drive wire is which on a unipolar stepper motor. This is the type of motor that I have most commonly found surplus or in salvage equipment 
Determining angle per step or steps per revolution of a stepper motor. 
Determining maximum speed of stepper motor. 
Demonstrating the operation of a stepper motor. 

Platform: Arduino ( I used the bare bones board, but any should do ).  Added an external 5 v regulator to power the servos and the laser pointer ( which I got from … ).  Software done using arduino.ext.   

A laser pointer is connected to 2 Servos and the servos are connected to each other so one controls the azimuth while the other controls the altitude ( like most standard cannons ).   ( controlled by the RS232 connection ): 

*Set  azimuth
*Set  altitude
*Save and recall azimuth and altitude
*“Tour” all the saved settings.

Example:


Hardware 

 

== Command Interface ==

All commands ( except stop should be terminated with a carriage return ) Note that the command interface is not very smart, giving parameters that are out of range my blow the whole program up. If so reboot the microcontroller . Do not send a new command ( except stop ) until earlier commands have been completed ( actually you can get ahead some if you are careful ). Commands may be either upper or lower case. The backspace key usually works.


{| class="wikitable"
|-valign="top"	
! Command
! Code
! Notes, Arduino Response
<!------------------------------->
|-valign="top"		
|Report version
|v
|Version of the software something like: 
Servo ver Dec 28b 2010
<!------------------------------->
|-valign="top"		
|Aim up
|unnn
d-
|Shift the aim up by nnn microseconds.  Software keeps pulse in legal 1 to 2 msec range.
<!------------------------------->
|-valign="top"		
|Aim down
|dnnn
d-
|Shift the aim down by nnn microseconds.  Software keeps pulse in legal 1 to 2 msec range.
<!------------------------------->
|-valign="top"		
|Where = Request aim position
|w
|tells fire point, index and x and y pulse delays.
<!------------------------------->
|-valign="top"		
|Report on all parameters
|r
|Delimited by commas something like:
Dir +1, Permutation 1, Stepper Pos 80, Step Delay Us = 300 .....
<!------------------------------->
|-valign="top"		
|Go for a number of steps
|gnnn
|go for a number of steps ( max. about 30,000 ) Direction set with d. 
Responds with "g starting<cr>" when rotation begins, then with "g done<cr>" when done.  May be stopped early with stop command.
<!------------------------------->
|-valign="top"		
|Set the time delay between steps in ms ( max 255 )
|tnnn
|Reports delay set.  nnn = 0 to 255
<!------------------------------->
|-valign="top"		
|Micro second delay in addition to to the ms delay.
|unnnn
|Reports delay set. Ok to use values nnn = as high as 5000 us.
<!------------------------------->
|-valign="top"		
|Set the permutation of the motor wires.
|pn
|Set the permutation, find the value that works for your motor. ( n = 0 to 5 ) Responds with the permutation set.
<!------------------------------->
|-valign="top"		
|Special command 1, Spin the motor in an interesting way.  
|x1
|Motor spins responds with "x special done<cr>" when it is done.  May be stopped with the stop cammand.
<!------------------------------->
|-valign="top"		
|Special command 2, Vibrate the motor first a lot then less and less to stop
|x2
|responds with "x special done<cr>" when it is done
<!------------------------------->
|-valign="top"		
|Stop 
|!
|Should almost immediately stop long running commands like Go or x1 or x2. Responds with  Stopped<cr> when stoped ( wich should be quick ).
<!------------------------------->
|-valign="top"		
|Other, not understood commands
|xxx
|Responds with "!Bad Command = xxx" if the command is not understood.
<!------------------------------->

|}


Notes on terminal program set up. 
Baud rate should be 19.2K 8N1, but is easily adjustable in the header file for the program. 
Most terminal programs can be set to treat a carriage return as a carriage return line feed. Do it. 

The alpha commands are case insensitive, use upper or lower case.

== Program Design ==

The program does not use the Arduino servo library ( ref would be nice ) or interrupts.  Instead it relys on polling comparing the current time ( mills() ) to a saved time to see if it is time for a new pulse.  This seems to be a common tenique, which I borrowed from the web. ( For some info on servo motors see: [http://opencircuits.com/Motors#Servo Motors] ).  Two variables store the time in microseconds for each pulse, this time is implemented using the delaymicroseconds() function.  See the function: xxx.  The Arduino PWM functions and hardware are not used: on most microcontrollers these give you good resolution in a 0 to 100% duty cycle, but not good for the 5% to 10% duty cycle used by servos ( this may or may not apply to the Arduino, I did not even check ).

The archive has 2 versions of the program the Simple Laser Cannon can only aim the laser left, right, up, down and does not save any setings or "fire" at any points.

In the more advanced version settings may be saved and recalled from 2 arrays ( one for X one for Y ).  Shifting to one of these arrays moves the laser to that "point" and we say it fires ( actually I leave the laser on all the time ).  The laser may also be sent on a tour of the defined points.

Most of the important constants are defined ( using #define ) in the servo header file.

I have tired to do a good job commenting the file, try reading it.  Email me if you have questions [[russ_hensel]].

Commands are received via an serial communications routine [[Arduino Command Interpreter]], the main loop checks each time around to see if a complete command has been received. Because commands are only interpreted in the main loop all commands are ignored until the program returns to the main loop. RS232 functions are not driven by an interrupt.

== Hardware ==

An Arduino of course, and to run the motors I used an external plug in dc supply of well over 5 volts and a 5 volt linear regulator to power the servos.  I left the arduino running off the usb port.  I bought a couple of laser pointer lasers ( a laser pointer without the case, batteries, and swithch, but with an adjustable lens ), I will try to find a refence when I order more.  I added 2 RC servo motors, one standard size, one micro.  Using a small peice of sheet stock, I drilled 2 holes in in and then using double sided foam tape and a nylon tie, fastened the servo to the sheet.  I fastened the smaller servo to the horn of the larger servo so the axies are at right angles.  Finally I tied on the laser to the horn of the small servo.  ( a picture will appear here, soon? ).  The laser is powered from the 5 volts thru a current limiting 200 ohm resistor ( a 150 or perhaps even 100 ohm resistor would give a brighter beam, at some point the beam gets too bright and the laser fails, experiment at your own risk.  My laser came without specs. )  In the program the output pins for the Arduino are defined in the header file.

[[Image:can1.png|alt text]]

The servos come with 3 pin female connectors, these can be plugged into 3 pin male headers, to plug them into the protoboard, make dual males like so:

[[Image:con1.png|alt text]]

[[Image:con2.png|alt text]]

I have some more discussion of this technique at:  [[Solderless protoboard]]

My bare bones board plugs right into the protoboard:  this one is a much bigger protoboard than I need even with the additional parts used for a stepper tester ( discussed at [[Stepper Motor Demonstration and Tester]] ).

[[Image:ard1.png|alt text]]

== Other Things to Try ==

*You can use the pointing feature of the system to implement an instrument with a very large scale:  Put a temperature scale on one side of the room, the "cannon" on the other and have it point to the temperature.  

*I have been thinking about a clock, each hour would be a piece of crystal and the laser would hit it on the hour.  Minutes might use another laser or other sort of display.

*Surely you can think of something.

== Additions/Changes ==

These are changes I may or may not make: ( or you may take them on ) 
 

== Possibly useful links ==

*This program uses my: [[Arduino Command Interpreter]]

*[[RS232]] Discusses the sort of interface that is used by this project. 

*More information on serial communications with microcontrollers: [[Microcontroller Serial Communications Articles]] 

*A free terminal program, I like this much better than hyperterminal: Welcome to our Free Download/New Products Page! http://www.rs485.com/psoftware.html

*[http://www.popsci.com/node/19965How|It Works: The Flying Laser Cannon] for a more distructive version.

== Download ==

email me to see if there have been some unposted revisions – which right now is all there is. [[russ_hensel]]


== Comment, Questions, Contributions?  ==

Email me [[russ_hensel]], or use the talk page for this topic. All feedback is welcome. 

[[category:Projects]][[category:Serial Communications]][[category:Microcontroller]][[category:Arduino]]