Driving up to 48 servos with a Spider controller
@ March 22, 2011
- CPU: ATmega1280 or ATmega2560
- Power source: 7.2V - 24V
- Programming language: Arduino C
| Attachment | Size |
|---|---|
| _48_servos_array.zip | 850 bytes |
This tip/walkthrough will work with all Arduino Mega PCBs and their clones. I have found the instructions for the servo command to be a little vague so in this tip I will share my research.
The Spider controller is an Arduino Mega compatible PCB. Unlike the Arduino Mega the Spider controller was designed specifically to drive a large number servos. This made it ideal for this tip/walkthrough.
The Arduino servo library is capable of driving up to 48 servos. After a bit of experimenting I found that the servos can be assigned to any of the digital pins from D0 to D63. For those thinking that the digital pins only go to D53, analog pins A0 - A9 are digital pins D54 - D63.
For those who have never used the servo command before I will start at the beginning using the attached code as my example. The first line of the code "#include <Servo.h>" means that the instructions needed to generate the servo control signals will be included in the code to be uploaded to the microcontroller.
Before the setup() function you must define your servos same as you define your global variables. I've simply called my servos s00 to s47. You should name your servos with descriptive names to make your program easier to read.
The Servo command uses a timer for each 12 servos used starting with Timer 5. As these timers are also used for commands like PWM you need to plan your pin assignments to avoid conflicts.
1 to 12 servos use timer 5 disabling PWM on pins 44,45 and 46.
13 to 24 servos use timers 1&5 disabling PWM on pins 11,12,44,45 and 46.
25 to 36 servos use timers 1,4&5 disabling PWM on pins 6,7,8,11,12,44,45 and 46.
37 to 48 servos use timers 1,3,4&5 disabling PWM on pins 2,3,5,6,7,8,11,12,44,45 and 46.
Once you have defined your servos you need to attach them to the physical pins of the controller. In the setup() function you can attach your servos to any of your digital outputs. In my sample I have avoided digital pins 0 and 1 as they are used for serial communications. At this point even thought the servos have been attached to a pin they are not receiving any signals.
The first time you write to a servo using either the servo write() or writeMicrosecond() command the pin will be initialised and the servo will receive a control signal. depending on your application you may need to initialise the servos in the setup() function. In my example I initialise the servos in the loop() function.
@ Fri, 2012-04-13 08:17
Adding Sweep?
I purchased a spider controller for an art installation I am doing in Chicago- it is beautiful. I have 40 servos running off the code provided here- thank you, it looks very cool.
Any hints on how I would go about applying the Servo Sweep that comes as an example in Arduino? To all 40 servos? I am new to all of this, however I know the basics of arduino/processing and mid-level in python. I am a skilled in rapid prototyping, so hopefully I can offer up help to someone in that area to return the favor. Not just a newbie without any skills to share! I'm sure this is easy, just thought I would check here first. thanks.
// Sweep
// by BARRAGAN <http://barraganstudio.com>
// This example code is in the public domain.
#include <Servo.h>
Servo myservo; // create servo object to control a servo
// a maximum of eight servo objects can be created
int pos = 0; // variable to store the servo position
void setup()
{
myservo.attach(9); // attaches the servo on pin 9 to the servo object
}
void loop()
{
for(pos = 0; pos < 180; pos += 1) // goes from 0 degrees to 180 degrees
{ // in steps of 1 degree
myservo.write(pos); // tell servo to go to position in variable 'pos'
delay(15); // waits 15ms for the servo to reach the position
}
for(pos = 180; pos>=1; pos-=1) // goes from 180 degrees to 0 degrees
{
myservo.write(pos); // tell servo to go to position in variable 'pos'
delay(15); // waits 15ms for the servo to reach the position
}
}
@ Fri, 2012-04-13 14:57
Servos as an array
I have updated the attached sample code. The new code is similar to the servo sweep example except that you can select how many servos from 1-48. Each servo can move at a different speed and / or direction.
@ Fri, 2012-04-13 18:36
That is very cool. I tried
That is very cool. I tried it this morning and it works great. Thank you very much... I will post pictures once it's finished. It's a 1ft x 30 ft, undulating strip of turf grass that hangs from the ceiling using an aluminum armature, 40 servos, piano wire and few other things. Setup could be applied to a crawling worm bot for sure.
@ Fri, 2012-04-13 18:53
I'm glad I could help
@ Mon, 2011-06-13 07:58
So will there be an option
So will there be an option to just get a board unpopulated or maybe the gerbers. And when will this beastie be available
@ Mon, 2011-06-13 15:58
The board is available from
@ Wed, 2011-04-06 19:04
Wahoo!
Looking at the back of the spider, it looks like ground and Vcc for the servo pins could be re-routed off-board from the back side. With the USB to the right, looking at the back of the board, the top left corner looks like a bottle neck for ground and Vcc that could be severed, and soldered for off board (leave ground connected of course).
@ Wed, 2011-03-30 19:58
What do you reckon the
What do you reckon the likely cost of this will be, OddBot. Just an idea.
@ Thu, 2011-03-31 03:36
Tough call
I can't say as it is up to the distributors. It should be roughly the same price as the Arduino Mega.
@ Wed, 2011-03-30 20:20
Whoa! For a moment I thought
Whoa! For a moment I thought that the Dagu Spider controller pictured as part of the Quadruped Walking Robot kit was for sale for only $29.
However, further reading showed me that "Motor controller, microcontroller, batteries sold separately". I haven't found the controller for sale in the wild yet.