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[on:]

Hi, im new to the arduino, but i have read up on the arduino, and i plan to start an animatronics project using the arduino. Im trying to make a biped robot. I plan to use a RS-7250 SBC connected to an arduino(s) witch connect to many digital servos. I need up to 20-24 servos. Also i will connect up 1 gyro and 1 accelerometer. I was wandering if someone would give me a rough idea of how this could lay out. If i could get all the servos to work on one digital line or would i need 3 to 4 arduino's connected to the SBC with 5-10 servos per a arduino. I could really use some help. Thanks.

[Reply #1 on:]

Although others may have their own opinions, I think that for so many servos you should offload that part of the work to a dedicated controller like this:

http://www.lynxmotion.com/Product.aspx?productID=395

Controls up to 32 servos, takes commands over serial.

Keeping 24 servos updated will eat up a lot of your computational effort. Also the wiring will be messy - the SSC-32 handles the servos for you and the wiring is already dones.

Of course there is satisfaction in doing it all yourself from scratch, and if that's the way you go make sure you let everyone know how!

[Reply #2 on:]

You could offload the driving of 20+ servos to one or two arduinos but it would take some tricky programming with interrupts and timers to get it going. The device linked by trialex seems a good way to go. btw, that board does look like it uses the same chip as the arduino  

[Reply #3 on:]

Google for 'OpenServo' and see if that might be of help.

It consists of an open hardware/software solution to convert a regular servo into a digital servo, but the result can be controlled over I2C, not just the good old pulse duration method.

This means you could give each servo its own address on the I2C bus and control them all with just two pins (analog 4 and 5, can't be changed cuz linked to hardware I2C on the atmel chip).

You would then send a two byte angle to a given servo's address and that servo will seek and hold that angle until a new order is sent. No need to maintain a pulse signal.

You can even pre-program move sequences from what I understand.

[Reply #4 on:]

Oh, do keep in mind servos are huge power hogs and 20+ of them will require separate power from the Arduino itself.

[Reply #5 on:]

Thanks alot, very much appericiate the help. I will definitly use a different powersource, and use the SSC-32 servo controller. So far this is the layout im planning, the SBC has 2 serial connections, 1 to the arduino and another to the SSC-32 controller. The Arduino will control the gyro and the accelerometer and plus any other sensor i may put on there. Also if anyone has any recomendations, i would much appericiate them. Also if there is a tutorial on how to get a gyro working with the Arduino that would help too. I already know how to get the accelerometer to work. Thanks again for yalls help.

[Reply #6 on:]

Also i was just thinking to keep my options open. Does anyone know how i can connect the ssc-32 serial board, a gyro, an accelerometer, and a speaker plus touch sensors without the SBC. I dont think the adurino is powerful enough or has enough ports to handle all of this without an SBC.  Thanks again for the help.