Serial Servo Controller w/Arduino - Control Up To 12 Servos At Once Using the Arduino and a USB Connection

I'm going to show you how to use your Arduino to control up to 12 servos at once with minimal jitter.  Using a simple serial interface you can control the position of up to 12 servo channels.  Up to 10 snapshot positions can be saved and played back at any time.  Start up values for each servo can be saved as well.

There are two major parts to the application.  The first part I will discuss is the firmware and hardware.  This includes the Arduino and another board we will use to supply power to the servos.  It's important to isolate the servo power supply from the microprocessor power in case the servos need more current than the battery can supply (imagine all 12 servos stalling at once).  If the power supplies are the same you could have a brownout condition on your microprocessor depending what type of power supply you are using.  I will also show you the firmware required to run this application on the Arduino.

In the second part I will discuss some simple software that will allow you to control the firmware through serial commands.  This software provides an interface to the Arduino firmware to control the servos, save servo start up positions, even record a series of positions, or frames, (of all channels saved at once) to playback in sequence when desired.  The software is .Net based so make sure you have the latest .Net framework installed.  I will be supplying an installer and source code.  

Here is a video demo of the project:

Step 1 Parts List

The following is a list of material and items I used for this instructable:

1x Arduino Board (Any variant that has a 328p processor)
1x BreadBoard
1x Battery 6.0-8.0Vdc (I used an 800maH LiPoly battery)
1x 1N4004 Diode
2x 220uF 35V Electrolytic Capacitors
4x 3 Pin Headers  (Use as many as you have servos for, I used 4 for this example but the firmware supports up to 12, just repeat)
4x 100 ohm resistors (1 for each servo.  These are used for current limiting.  At 3.3v the resistor limits the amount of current through the microprocessor at 3.3ma if a low impedance load is seen)
1x Small LED
1x 470 ohm resistor
1x Switch (I used a DIP switch for simplicity)
 4x Hobby Servos
Various Jumper Wires

Comments

[rocketman221]

Cool project.
It would be nice to have a web interface so I could control it with any wifi enabled tablet. I think it can be done with php.

[soshimo]

Thanks for the feedback!

I wish I had made the command handling more modular, maybe that's something I can work on. That way you could abstract the handling out and use any transport mechanism you want. In this example it's RS232, for your idea it would TCP/IP. Heck, you could even go wireless with Zigbee or something and really have some power.

[rocketman221]

I was actually thinking of using some wireless serial transmitters from sparkfun to connect the arduino to a serial port on my server.
But I was considering making pan/tilt mounts with servos for a couple of small security cameras.

[megaduty]

Thanks Soshimo! This could help me with my 4 servo and 6 servo biped project.

[soshimo]

Glad to help. Sweet looking 3d printed parts there. Maybe you can do an instructable when it's done. There is a new contest coming up that this would be a perfect fit for - grand prize is a $50k 3D printer. Feel free to use whatever you need from my instructable and happy hacking!

[cupolo]

is what I was looking for a long time thanks so much ....... very nice ;)

[bqbowden]

I have a prject for an ardiuno to control groups of selenoids on a schedule. Can you suggest a resurce where I can build this kind of circuit?

[soshimo]

I would start with the Arduino Playground [http://arduino.cc/playground/]. There are plenty of examples of using an Arduino to control a solenoid. Just extend one of those examples into a scheduler which shouldn't be too hard to do - plenty of examples of writing a generic scheduler on the web.

[njkl44]

take a look at my project:
http://www.instructables.com/id/Arduino-Wireless-Animatronic-Hand/
i control 5 servos just by power from arduino and no resistors or anything. I am currently powering 7 right now but i have a lipo im using

[soshimo]

I had brownout problems early on with a PTZ camera I was using to control from the Arduino so I've always been wary of using the power from the board. If you are powering from USB the maximum current you can source is 500-900ma. If from a walwart usually around 750-1000ma. I guess you can power your arduino from a lipo as well, but coming from the RC world (fixed and rotor wing craft) it's always a good idea to separate your command/logic supply from your servo/motor supply. As the motor battery drains, which they all do quickly during flight, you may lose control to your craft and suffer a catastrophic crash.

[future-tinker]

cool!

[soshimo]

Thank you sir! It was my first instructable so I was a little nervous about it. I almost had as much fun documenting it as I had creating it, plus it forced me to fix a lot of little nagging things.