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Peoria, IL
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I am just starting into robotics. I am working on designing a build for a biped humanoid with about 23 digital servos. I need to choose a board that will let me grow. Down the line I would like to add sound, lighting, voice control, sensors, wireless,  etc. He will be a dancer.

This is my build list so far. I just started putting it together yesterday so it is still in the very early stage. It will be made from Lynxmotion parts.
      
1   BPS-NS   Biped Scout (no servos, no electronics)
Lexan Components
5x Aluminum "C" Servo Bracket with Ball Bearings Two Pack (ASB-09)
2x Aluminum Multi-Purpose Servo Bracket Two Pack (ASB-04)
2x Aluminum Dual Inline Multi-Purpose Servo Bracket Single Pack (ASB-15)
1x Aluminum Long "C" Servo Bracket with Ball Bearings Two Pack (ASB-10)
1x Aluminum 15-degree Ankle Bracket Two Pack (ASB-17)
1x Aluminum Robot Foot (Pair) (ARF-02)
1x E-Z Aluminum Servo Bracket (One Pair) (ASB-02)
1x SES Electronics Carrier (EC-02)


2   RH-01   Robot Hand - A Single (no servos)
1   BT-01           Humanoid Biped Torso - A (no servos)
3   ASB-04       Multi-Purpose Servo Bracket Two Pack (Arms)
1   ASB-06      "L" Connector Bracket Two (Arms)
1   ASB-09      "C" Servo Bracket w/ Ball Bearings Two Pack (Arms)
1   ASB-11      Offset Servo Bracket w/ Ball Bearings Two Pack (Arms)
1   RB-Hit-108   HPP-21 Digital Servo Programmer
2   RB-Dfr-105   DFRobot Rainbow LED Ring (Arduino Compatible)
19   HRC35485S   Hitec HS-5485HB Standard Karbonite Gear Digital Universal Servo
4   HRC35645S   Hitec HS-5645MG High-Torque 2BB Metal Gear Universal Servo

I'll be using the four higher torque servos for the shoulders and hips.

I build my own computers(I started learning on DOS) and am into RC multirotor helicopters. I also have over 25 years experience in Commercial Sound and Special Effect Lighting Systems. I can design, install and program killer systems.

I'd like to keep my initial controller under $100.00. My total budget to start will be between $1,200.00-$1,500.00. I usually end up spending more.

I am going to see if I can throw this together in a CAD program using the CAD files from Lynxmotion. I probably have more servos than I need but I like having extras whenever I do any hobby.  I am thinking down the road I would like to give him a tail or an extending neck. Maybe give him a Harvey Keitel head reminiscent of the robot in the movie Saturn 3, Hector.
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Sounds like you need a 2560. Has 16 PWM channels that will let you control 32 or 48 servos I think.
Mega has 54 IO lines broken out. Be good for initial development, then exand to a standalone board to get to access All of the 84 IO lines the 2560 offers.
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the land of sun+snow
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Lynxmotion already has most of the electronics aspect covered. I would definitely get
the SSC-32 servo controller, and not try to control the servos directly from an Arduino.
Much much too much trouble for a walker with many DOF. You really want a dedicated
servo controller for that.

But now the problem comes in. If you want to use an Arduino as the master controller,
you talk to the SSC-32 using an RS232 port. Since this is a walker, it would be nice to
use a smallish sized pcb - such as an Arduino-UNO - but the UNO only has a single
"hardware" RS232 UART, and the Arduino software UARTs really don't work all that well.

So, best to find an Arduino board with UNO form-factor but with a better chip than
the 328, ie more than 1 h.w. UART. Then, you can do SSC-32 comms simultaneously
with connection to the PC for s.w. development.
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Peoria, IL
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I did add the SSC-32 Servo controller to the list. I liked the look of the software for programming movements and setting limits. It reminds me of programming moving mirror and moving head intelligent lights.

I don't mind using the Arduino Mega 2560 Microcontroller Rev3. I like bigger. I am thinking of beefing up the leg servos to be able to carry a 3S lipo and use a 15amp UBEC that will drop the voltage from 11.1v down to 5v or 6v to power things since I already have those parts. The 11.1v can power the 2560

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If you want to go with the Mega 2560 board, then you'll have extra h.w. UARTs.

11.6V is a little high to power the Mega bd with, although it's probably indicated as
being within the allowable range. The problem is those weensey smt v.regs on the
bds will get hot if there is a large voltage drop across them, and the load current
is too high. Eg,

Pd = (11.6V - 5V) * 75 mA = 0.5 watt, which is about what those devices can dissipate.
IOW, not even close to 1 Amp.
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This is what is stated on the arduiino website for the board.

The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

The power pins are as follows:

VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.

5V. This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.

GND. Ground pins.

IOREF. This pin on the Arduino board provides the voltage reference with which the microcontroller operates. A properly configured shield can read the IOREF pin voltage and select the appropriate power source or enable voltage translators on the outputs for working with the 5V or 3.3V.

If I can use some of the 3S lipos that I already have it would make things easier. I have a decent 20amp charger that can also handle NiCd/NiMH batteries from 1 – 18 cells so if I have to go with NICd's it is no big deal.

Thank you guys for your help! I appreciate it.
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